Clinical Approach to Neuropathic Pain
Comprehensive Practical Framework1. Symptom Overview
Understanding the clinical significance and classification of neuropathic pain
Neuropathic pain affects approximately 7-10% of the general population worldwide, making it one of the most common chronic pain conditions encountered in clinical practice. It accounts for up to 25% of all chronic pain presentations and is responsible for significant healthcare utilization, with patients averaging 12-15 physician visits annually for pain management. The economic burden is substantial, with annual costs estimated at $40,000-$60,000 per patient when accounting for direct medical expenses, lost productivity, and disability. Despite its prevalence, neuropathic pain remains underdiagnosed in approximately 50% of cases, often being misattributed to musculoskeletal or psychogenic causes.
Definition
Neuropathic pain is defined by the International Association for the Study of Pain as “pain caused by a lesion or disease of the somatosensory nervous system.” This definition requires demonstrable evidence of nervous system damage affecting sensory pathways, distinguishing it from nociceptive pain (arising from tissue damage) and nociplastic pain (arising from altered nociceptive processing without clear tissue or nerve damage). The somatosensory system includes peripheral nerves, dorsal root ganglia, spinal cord, brainstem, thalamus, and cortical sensory areas.
Classification by Duration
| Category | Duration | Common Causes | Clinical Significance |
|---|---|---|---|
| Acute | Less than 4 weeks | Acute herpes zoster, traumatic nerve injury, postoperative nerve damage, acute radiculopathy | Early intervention may prevent chronification; aggressive treatment recommended to reduce risk of persistent pain |
| Subacute | 4 weeks to 3 months | Evolving postherpetic neuralgia, chemotherapy-induced neuropathy, early diabetic neuropathy | Critical window for intervention; neural plasticity changes becoming established; reversibility still possible |
| Chronic | Greater than 3 months | Established diabetic polyneuropathy, postherpetic neuralgia, post-stroke pain, phantom limb pain | Central sensitization often established; requires multimodal management approach; complete resolution uncommon |
Classification by Anatomical Location
Peripheral Neuropathic Pain
Definition: Pain arising from lesions or diseases affecting the peripheral nervous system, including peripheral nerves, plexuses, dorsal root ganglia, and nerve roots.
Characteristics: Often follows a dermatomal or peripheral nerve distribution; may be associated with identifiable sensory loss; frequently accompanied by positive sensory phenomena.
Examples: Diabetic polyneuropathy, postherpetic neuralgia, trigeminal neuralgia, carpal tunnel syndrome, radiculopathy.
Central Neuropathic Pain
Definition: Pain arising from lesions or diseases affecting the central nervous system, including the spinal cord, brainstem, thalamus, or cerebral cortex.
Characteristics: Often diffuse or poorly localized; may not follow typical dermatomal patterns; frequently associated with other neurological deficits.
Examples: Post-stroke pain (central post-stroke pain syndrome), multiple sclerosis-associated pain, spinal cord injury pain, syringomyelia.
Classification by Distribution Pattern
| Pattern | Description | Suggests |
|---|---|---|
| Length-dependent (stocking-glove) | Symmetric, distal-to-proximal progression affecting longest nerves first; begins in feet, progresses to ankles, then hands | Metabolic or toxic polyneuropathy: diabetes mellitus, alcohol, chemotherapy, vitamin B12 deficiency |
| Dermatomal | Pain confined to one or more specific dermatomes; often unilateral | Radiculopathy, postherpetic neuralgia, nerve root compression |
| Single nerve territory | Pain limited to the distribution of a single peripheral nerve | Mononeuropathy: carpal tunnel syndrome, ulnar neuropathy, meralgia paresthetica, trigeminal neuralgia |
| Multiple mononeuropathy (mononeuritis multiplex) | Asymmetric involvement of multiple individual nerves; random, non-contiguous distribution | Vasculitis, diabetes mellitus, leprosy, sarcoidosis, hereditary neuropathy with liability to pressure palsies |
| Proximal and asymmetric | Affects proximal limb muscles and sensory territories; often painful with weakness | Diabetic amyotrophy (diabetic lumbosacral radiculoplexus neuropathy), neuralgic amyotrophy |
| Hemibody or regional | Affects one side of the body or a large region not conforming to peripheral nerve or dermatomal patterns | Central neuropathic pain: post-stroke pain, multiple sclerosis, thalamic lesions |
Classification by Symptom Quality
Spontaneous Pain
Continuous: Constant burning, aching, or squeezing pain present without provocation.
Paroxysmal: Intermittent attacks of shooting, lancinating, or electric shock-like pain lasting seconds to minutes.
Evoked Pain
Allodynia: Pain from stimuli that are not normally painful (light touch, clothing contact, temperature changes).
Hyperalgesia: Exaggerated pain response to mildly painful stimuli.
Abnormal Sensations
Paresthesias: Abnormal sensations such as tingling, pins and needles, or numbness.
Dysesthesias: Unpleasant abnormal sensations, whether spontaneous or evoked.
Key Concept: The “Big Five” Causes of Neuropathic Pain
Five conditions account for approximately 80% of neuropathic pain cases seen in clinical practice:
- Painful diabetic polyneuropathy — affects 20-25% of diabetic patients; most common cause worldwide
- Postherpetic neuralgia — develops in 10-20% of herpes zoster cases; risk increases with age
- Lumbar and cervical radiculopathy — nerve root compression from disc herniation or stenosis
- Chemotherapy-induced peripheral neuropathy — affects 30-70% of patients depending on agent
- Trigeminal neuralgia — most common facial neuropathic pain syndrome
Impact on Quality of Life
| Domain | Impact | Frequency |
|---|---|---|
| Sleep disturbance | Difficulty falling asleep, frequent awakening, non-restorative sleep | 60-80% of patients |
| Mood disorders | Depression, anxiety, irritability; bidirectional relationship with pain | 40-60% of patients |
| Functional impairment | Reduced mobility, difficulty with activities of daily living, work disability | 50-70% of patients |
| Social withdrawal | Reduced social activities, relationship strain, isolation | 40-50% of patients |
| Cognitive effects | Difficulty concentrating, memory problems (often medication and pain-related) | 30-40% of patients |
2. Pathophysiology and Mechanisms
Understanding the underlying mechanisms of neuropathic pain
Understanding the pathophysiology of neuropathic pain is essential for rational treatment selection, as different mechanisms respond to different therapeutic interventions. Neuropathic pain arises from maladaptive changes in the nervous system following injury or disease, involving complex interactions between peripheral and central mechanisms. These changes can persist long after the initial insult has resolved, explaining the chronic nature of many neuropathic pain conditions.
The Somatosensory Pain Pathway
| Component | Structure | Function |
|---|---|---|
| Primary Afferents | A-delta fibers (myelinated, fast), C fibers (unmyelinated, slow) | Detect and transmit noxious stimuli from periphery to spinal cord; A-delta mediates sharp, well-localized pain; C fibers mediate dull, burning, poorly localized pain |
| Dorsal Root Ganglion | Cell bodies of primary sensory neurons located outside spinal cord | Integration and modulation of sensory signals; site of gene expression changes in neuropathic states; increasingly recognized as therapeutic target |
| Spinal Cord Dorsal Horn | Laminae I, II (substantia gelatinosa), and V; second-order neurons | First site of synaptic transmission and modulation; integration of ascending and descending signals; site of central sensitization |
| Ascending Pathways | Spinothalamic tract (lateral), spinoreticular tract, spinomesencephalic tract | Transmit pain signals to brainstem and thalamus; different tracts mediate sensory-discriminative versus affective-motivational components |
| Thalamus | Ventral posterolateral nucleus, medial thalamic nuclei, posterior thalamic nuclei | Relay and processing of pain information; integration with other sensory modalities; projects to cortical areas |
| Cortical Areas | Primary and secondary somatosensory cortex, anterior cingulate cortex, insular cortex, prefrontal cortex | Conscious perception, localization, and emotional processing of pain; executive function and pain-related decision making |
| Descending Modulation | Periaqueductal gray, rostral ventromedial medulla, locus coeruleus | Endogenous pain modulation (both inhibitory and facilitatory); dysfunction contributes to chronic pain; target for antidepressant analgesics |
Key Pathophysiological Mechanisms
Peripheral Sensitization
Definition: Increased excitability and reduced threshold of peripheral nociceptors following nerve injury or inflammation.
Mechanisms:
- Upregulation of voltage-gated sodium channels (especially Nav1.7, Nav1.8, Nav1.9)
- Release of inflammatory mediators (prostaglandins, bradykinin, nerve growth factor)
- Recruitment of silent nociceptors
- Phenotypic switch in A-beta fibers to express substance P
Clinical correlate: Primary hyperalgesia, spontaneous pain at injury site
Central Sensitization
Definition: Increased excitability of neurons in central pain pathways, leading to enhanced responsiveness to normal inputs.
Mechanisms:
- NMDA receptor activation and calcium influx
- Wind-up phenomenon (temporal summation)
- Long-term potentiation in dorsal horn
- Glial cell activation (microglia, astrocytes)
- Loss of GABAergic inhibitory interneurons
Clinical correlate: Secondary hyperalgesia, allodynia, expanded receptive fields
Ectopic Discharge and Ion Channel Dysfunction
| Mechanism | Description | Clinical Manifestation | Therapeutic Target |
|---|---|---|---|
| Ectopic discharge | Spontaneous firing from damaged nerve fibers or dorsal root ganglion; occurs at neuroma sites or along demyelinated segments | Spontaneous shooting or electric shock-like pain; paresthesias | Sodium channel blockers (carbamazepine, oxcarbazepine, lidocaine) |
| Sodium channelopathy | Altered expression and distribution of Nav1.3, Nav1.7, Nav1.8 channels; gain-of-function mutations in inherited conditions | Burning pain, erythromelalgia, small fiber neuropathy symptoms | Sodium channel blockers; Nav1.7-selective agents in development |
| Calcium channel dysfunction | Upregulation of alpha-2-delta subunit of voltage-gated calcium channels in dorsal root ganglion and spinal cord | Enhanced neurotransmitter release, increased excitability | Gabapentinoids (gabapentin, pregabalin) bind alpha-2-delta subunit |
| Potassium channel downregulation | Reduced expression of hyperpolarizing potassium channels following nerve injury | Increased neuronal excitability, repetitive firing | Potassium channel openers (retigabine – limited use due to adverse effects) |
| TRP channel sensitization | Increased expression and sensitization of transient receptor potential channels (TRPV1, TRPA1, TRPM8) | Heat and cold hypersensitivity, chemical sensitivity | Capsaicin (TRPV1 desensitization); TRP antagonists in development |
Descending Modulatory Pathway Dysfunction
Clinical Relevance: The descending pain modulatory system normally balances facilitatory and inhibitory influences on spinal cord neurons. In chronic neuropathic pain states, this balance shifts toward facilitation, amplifying pain signals. This explains the efficacy of serotonin-norepinephrine reuptake inhibitors (such as duloxetine and venlafaxine) and tricyclic antidepressants in neuropathic pain — they enhance descending inhibition.
| Component | Normal Function | Changes in Neuropathic Pain |
|---|---|---|
| Serotonergic pathways | Predominantly inhibitory via 5-HT1A receptors; some facilitation via 5-HT3 | Reduced serotonergic inhibition; shift toward facilitation |
| Noradrenergic pathways | Inhibitory via alpha-2 adrenergic receptors in spinal cord | Reduced noradrenergic tone; diminished alpha-2 mediated inhibition |
| Endogenous opioid system | Inhibitory via mu, delta, kappa receptors; endorphins, enkephalins | Receptor downregulation; reduced opioid responsiveness; explains limited opioid efficacy |
| Endocannabinoid system | Modulatory via CB1 and CB2 receptors; affects both peripheral and central pain processing | Altered tone; potential therapeutic target for cannabinoid-based treatments |
How Specific Conditions Cause Neuropathic Pain
| Condition | Primary Mechanism | Treatment Implication |
|---|---|---|
| Diabetic polyneuropathy | Metabolic injury (polyol pathway, advanced glycation end products), microvascular ischemia, oxidative stress leading to small fiber damage and sodium channel upregulation | Glycemic control may slow progression; gabapentinoids and duloxetine target central sensitization; alpha-lipoic acid may address oxidative stress |
| Postherpetic neuralgia | Viral destruction of sensory neurons in dorsal root ganglion; loss of inhibitory interneurons in spinal cord; central sensitization from prolonged afferent barrage | Early antiviral treatment reduces risk; gabapentinoids and tricyclics for established pain; topical lidocaine for peripheral component |
| Trigeminal neuralgia | Neurovascular compression causing focal demyelination; ephaptic transmission (cross-talk) between adjacent nerve fibers; ectopic discharge generation | Sodium channel blockers (carbamazepine, oxcarbazepine) suppress ectopic activity; microvascular decompression addresses cause |
| Chemotherapy-induced peripheral neuropathy | Direct neurotoxicity affecting dorsal root ganglion neurons (platinum compounds) or microtubule disruption (taxanes, vinca alkaloids); mitochondrial dysfunction | Dose modification primary prevention; duloxetine only agent with evidence for treatment; gabapentinoids commonly used |
| Post-stroke pain (central post-stroke pain) | Lesion of spinothalamic pathway or thalamus; disinhibition of pain-processing areas; maladaptive cortical reorganization | Tricyclic antidepressants or lamotrigine; often refractory to standard treatments; may require combination therapy |
| Spinal cord injury pain | Deafferentation, loss of descending inhibition, glial activation, central sensitization at and below level of injury | Gabapentinoids first-line; may require multimodal approach; neuromodulation (spinal cord stimulation) for refractory cases |
| Painful radiculopathy | Mechanical compression plus chemical inflammation from nucleus pulposus; dorsal root ganglion sensitization; secondary central sensitization | Address mechanical cause when possible; gabapentinoids for radicular component; epidural steroids reduce inflammation |
Neuroplasticity and Pain Chronification
Maladaptive Changes
- Synaptic plasticity: Long-term potentiation in pain pathways
- Structural reorganization: Sprouting of A-beta fibers into lamina II
- Glial activation: Microglia and astrocyte proliferation; cytokine release
- Gene expression changes: Altered transcription of ion channels, receptors, neurotransmitters
- Cortical reorganization: Changes in somatotopic maps; altered connectivity
Factors Promoting Chronification
- Prolonged nociceptive input: Early, aggressive treatment reduces chronification risk
- Psychological factors: Catastrophizing, depression, anxiety amplify central sensitization
- Sleep disturbance: Impairs descending inhibition and promotes sensitization
- Genetic predisposition: Polymorphisms in COMT, GCH1, sodium channels
- Epigenetic modifications: DNA methylation, histone modifications in pain genes
Often Overlooked Mechanism: The Dorsal Root Ganglion
The dorsal root ganglion is increasingly recognized as a critical site in neuropathic pain pathophysiology. Unlike spinal cord neurons, dorsal root ganglion neurons are not protected by the blood-brain barrier, making them vulnerable to circulating toxins, metabolites, and immune mediators. This explains why:
- Diabetic neuropathy and chemotherapy-induced neuropathy preferentially affect sensory neurons
- Herpes zoster virus persists in dorsal root ganglion and reactivates to cause shingles
- Dorsal root ganglion-targeted therapies (such as dorsal root ganglion stimulation) can be effective when spinal cord stimulation fails
- Satellite glial cells surrounding dorsal root ganglion neurons contribute to pain through cytokine release
3. History Taking
A comprehensive approach to eliciting the neuropathic pain history
Red Flags — Require Urgent Evaluation
- Rapid progression of weakness — Guillain-Barré syndrome, vasculitic neuropathy, compressive lesion
- Bowel or bladder dysfunction — Cauda equina syndrome, spinal cord compression
- Saddle anesthesia — Cauda equina syndrome requiring emergency imaging
- Severe unilateral facial pain with corneal numbness — Trigeminal nerve infiltration by tumor
- Weight loss greater than 10% with new neuropathy — Malignancy, paraneoplastic syndrome
- Fever with rapidly progressive neuropathy — Infectious or inflammatory etiology
- Known malignancy with new neurological symptoms — Metastatic disease, leptomeningeal carcinomatosis
- Asymmetric motor neuropathy in diabetic patient — Diabetic amyotrophy, but rule out compression
- Autonomic symptoms (syncope, orthostatic hypotension, gastroparesis) — Autonomic neuropathy, amyloidosis
- Sudden onset hemibody sensory loss — Stroke, spinal cord infarction
Systematic History: The “BURNING” Approach
Use the mnemonic “BURNING” to ensure comprehensive neuropathic pain history taking:
- B — Burning and other descriptors: What does the pain feel like? Burning, shooting, electric, stabbing, tingling, numbness? Spontaneous or evoked?
- U — Underlying cause and onset: When did it start? Was there an identifiable trigger (injury, surgery, infection, new medication, diagnosis of diabetes)?
- R — Region and radiation: Where exactly is the pain? Does it follow a dermatomal or peripheral nerve distribution? Is it symmetric or asymmetric?
- N — Negative and positive symptoms: Are there areas of numbness (negative)? Tingling, allodynia, hyperalgesia (positive)? Both often coexist.
- I — Impact and intensity: How severe is the pain (0-10 scale)? How does it affect sleep, work, mood, daily activities? Use validated tools (Brief Pain Inventory).
- N — Night and timing patterns: Is pain worse at night (common in diabetic neuropathy)? Constant or intermittent? Paroxysmal attacks?
- G — General history and medications: Diabetes, alcohol use, chemotherapy, HIV, B12 deficiency, thyroid disease? Current medications including those that cause neuropathy?
Targeted Questions by Suspected Cause
| Suspected Cause | Key Features | Ask This Question |
|---|---|---|
| Diabetic polyneuropathy | Symmetric, length-dependent, burning feet worse at night, numbness | “Do your feet burn more at night? Do you have trouble feeling the floor when you walk? How long have you had diabetes and what is your usual blood sugar control?” |
| Postherpetic neuralgia | Dermatomal distribution, history of shingles rash, allodynia to light touch | “Did you have a painful rash with blisters in this area before the pain started? Does light touch from clothing make the pain worse?” |
| Trigeminal neuralgia | Unilateral facial pain, brief electric shock-like attacks, triggered by touch or movement | “Is the pain triggered by chewing, talking, brushing your teeth, or touching your face? How long does each attack last — seconds or minutes?” |
| Chemotherapy-induced peripheral neuropathy | Onset during or after chemotherapy, symmetric stocking-glove, dose-dependent | “Which chemotherapy drugs did you receive? When did the symptoms start in relation to treatment? Have symptoms improved, stayed the same, or worsened since completing treatment?” |
| Radiculopathy | Dermatomal distribution, radiating pain, may have associated weakness | “Does the pain shoot down your arm or leg? Does coughing, sneezing, or straining make it worse? Do you have any weakness or difficulty with specific movements?” |
| Carpal tunnel syndrome | Median nerve distribution, nocturnal symptoms, thenar weakness | “Do you wake up at night with numbness or tingling in your hand? Do you need to shake your hand to relieve it? Which fingers are affected?” |
| Small fiber neuropathy | Burning pain, normal strength and reflexes, may have autonomic symptoms | “Do you have burning pain with relatively preserved sensation to touch? Any changes in sweating, dry eyes or mouth, or lightheadedness when standing?” |
| Alcoholic neuropathy | Length-dependent, painful, associated nutritional deficiencies | “How much alcohol do you drink daily or weekly? For how many years? Have you had any nutritional problems or difficulty eating?” |
| Central post-stroke pain | Hemibody distribution, onset weeks to months after stroke, often thalamic | “When did you have your stroke and when did this pain begin? Does the pain affect the same side as your stroke weakness? What does it feel like?” |
| Multiple sclerosis-related pain | Variable distribution, may be paroxysmal (trigeminal neuralgia-like) or continuous | “Do you have a diagnosis of multiple sclerosis? Is this pain new or has it changed? Do you have Lhermitte’s sign — electric sensations down your spine when bending your neck?” |
Characterizing Neuropathic Pain Quality
Screening Tools for Neuropathic Pain
Several validated questionnaires help identify neuropathic pain based on symptom descriptors:
- DN4 (Douleur Neuropathique 4): 10 items; score ≥4 suggests neuropathic pain; sensitivity 83%, specificity 90%
- painDETECT: 9 items; score >18 indicates likely neuropathic pain; useful for mixed pain states
- LANSS (Leeds Assessment of Neuropathic Symptoms and Signs): 7 items; score ≥12 suggests neuropathic pain
- Neuropathic Pain Symptom Inventory (NPSI): Quantifies different neuropathic pain dimensions; useful for monitoring treatment response
Key descriptors favoring neuropathic pain: burning, shooting, electric shock-like, tingling, pins and needles, numbness, pain from light touch (allodynia).
Medication and Substance History
Medications That Cause Neuropathy
- Chemotherapy agents — Platinum compounds (cisplatin, oxaliplatin), taxanes (paclitaxel, docetaxel), vinca alkaloids (vincristine), bortezomib, thalidomide
- Antibiotics — Metronidazole (prolonged use), nitrofurantoin, fluoroquinolones, isoniazid (without pyridoxine), linezolid
- Antiretrovirals — Didanosine, stavudine, zalcitabine (older nucleoside reverse transcriptase inhibitors)
- Cardiovascular drugs — Amiodarone, hydralazine, statins (rare)
- Other — Colchicine, phenytoin, disulfiram, dapsone, gold compounds
Substances and Exposures
- Alcohol: Duration and quantity; associated thiamine deficiency; typically length-dependent painful neuropathy
- Industrial toxins: Lead, arsenic, mercury, thallium, acrylamide, organophosphates, n-hexane (glue sniffing)
- Recreational drugs: Nitrous oxide abuse (B12 depletion), cocaine-adulterant levamisole
- Nutritional factors: Bariatric surgery, malabsorption, restrictive diets, eating disorders — risk of B12, thiamine, copper, vitamin E deficiency
Relevant Medical and Family History
| History Element | Relevance | Key Questions |
|---|---|---|
| Diabetes mellitus | Most common cause of polyneuropathy; duration and control predict severity | Type 1 or 2? Duration? Recent HbA1c? History of retinopathy or nephropathy? |
| Malignancy | Chemotherapy-induced neuropathy; paraneoplastic syndromes; nerve infiltration | Cancer type and stage? Chemotherapy regimen? Any recurrence concerns? |
| Autoimmune disease | Vasculitic neuropathy, Sjögren syndrome, lupus, rheumatoid arthritis | Any diagnosed autoimmune conditions? Dry eyes or mouth? Joint pain? Rashes? |
| Kidney disease | Uremic neuropathy; medication dosing considerations | Any kidney problems? On dialysis? Recent creatinine level? |
| Thyroid disease | Hypothyroidism associated with neuropathy and carpal tunnel syndrome | Thyroid problems? On thyroid medication? Any recent thyroid tests? |
| HIV infection | HIV-associated sensory neuropathy; antiretroviral-induced neuropathy | HIV status? If positive, viral load and CD4 count? Current medications? |
| Family history | Hereditary neuropathies (Charcot-Marie-Tooth); familial amyloidosis | Any family members with neuropathy, high arches, hammer toes, or difficulty walking? |
| Surgical history | Post-surgical nerve injury; bariatric surgery (nutritional); spine surgery | Any surgeries near the area of pain? Bariatric surgery? Taking vitamins? |
Functional and Psychosocial Assessment
Functional Impact
- Sleep: Difficulty falling asleep? Night awakenings due to pain?
- Mobility: Balance problems? Falls? Use of assistive devices?
- Work: Able to perform job duties? Days missed?
- Daily activities: Dressing, grooming, cooking, driving?
- Exercise: Able to exercise? Limited by pain or weakness?
Psychosocial Factors
- Mood: Depression and anxiety screening (PHQ-2, GAD-2)
- Catastrophizing: Does patient feel helpless about pain?
- Social support: Family involvement, caregiver burden?
- Substance use: Opioid use, alcohol, illicit drugs?
- Expectations: What does patient hope to achieve with treatment?
4. Physical Examination
A systematic approach to examining patients with suspected neuropathic pain
Systematic Framework: Use the “General to Focused” approach for complete examination of patients presenting with neuropathic pain. Begin with general inspection, then systematically assess each sensory modality, motor function, reflexes, and autonomic signs. The pattern of findings guides localization and differential diagnosis.
General Inspection
- Gait: Observe for steppage gait (foot drop), ataxic gait (sensory ataxia from proprioceptive loss), antalgic gait (pain avoidance)
- Stance: Romberg test — positive suggests proprioceptive loss; worse with eyes closed
- Posture: Guarding of painful areas; asymmetric posture suggesting radiculopathy
- Skin changes: Trophic changes (shiny skin, hair loss), color changes (erythromelalgia), ulcers (insensate feet), scars (prior surgery or trauma), vesicular rash or scarring (herpes zoster)
- Muscle bulk: Focal atrophy (suggests motor involvement, denervation); pes cavus and hammer toes (hereditary neuropathy)
- Foot deformities: High arches, hammer toes — suggest hereditary neuropathy (Charcot-Marie-Tooth disease)
Vital Signs
| Vital Sign | What to Look For | Clinical Significance |
|---|---|---|
| Blood Pressure | Orthostatic hypotension: measure supine and standing (drop ≥20 mmHg systolic or ≥10 mmHg diastolic within 3 minutes) | Autonomic neuropathy (diabetic, amyloid); guides medication choices (avoid tricyclics if significant orthostasis) |
| Heart Rate | Resting tachycardia; loss of heart rate variability; fixed heart rate | Cardiac autonomic neuropathy; associated with increased cardiovascular mortality in diabetes |
| Temperature | Fever in context of rapidly progressive neuropathy | Suggests infectious or inflammatory etiology; may indicate vasculitis |
| Respiratory Rate | Tachypnea, shallow breathing, use of accessory muscles | Respiratory muscle weakness in Guillain-Barré syndrome — requires urgent monitoring |
| Oxygen Saturation | Desaturation, especially when supine | May indicate diaphragmatic weakness; concerning in Guillain-Barré syndrome |
Sensory Examination
Test each modality systematically, comparing side to side and proximal to distal. Map the distribution of any abnormalities to determine if they follow a dermatomal, peripheral nerve, or length-dependent pattern.
Small Fiber Function (Pain and Temperature)
| Test | How to Perform | Abnormal Finding | Interpretation |
|---|---|---|---|
| Pinprick sensation | Use disposable pin; compare sharp versus dull; test distally and move proximally to find sensory level | Reduced or absent sharp sensation; hyperalgesia (increased pain); allodynia | A-delta fiber dysfunction (sharp); C-fiber dysfunction (dull ache) |
| Temperature sensation | Use cold tuning fork or cool metal object; compare warm versus cool | Inability to distinguish warm from cool; paradoxical sensations | Small fiber (C-fiber) dysfunction; often affected early in diabetic and small fiber neuropathy |
Large Fiber Function (Vibration and Proprioception)
| Test | How to Perform | Abnormal Finding | Interpretation |
|---|---|---|---|
| Vibration sense | 128 Hz tuning fork on bony prominence (great toe, medial malleolus, finger); patient reports when vibration stops; compare to examiner’s sensation | Reduced duration compared to proximal sites or examiner; absent at distal sites | Large fiber (A-beta) dysfunction; posterior column involvement |
| Proprioception (joint position sense) | Hold digit by sides; move up or down while patient’s eyes closed; test great toe, then ankle if abnormal | Inability to detect direction of movement; errors in position sense | Large fiber dysfunction; sensory ataxia; posterior column disease |
| Light touch | Cotton wisp or 10-g monofilament; patient reports when touched with eyes closed | Reduced or absent sensation; 10-g monofilament test negative at foot sites predicts ulcer risk | A-beta fiber dysfunction; monofilament testing standard for diabetic foot screening |
Special Sensory Tests for Neuropathic Pain
| Test | How to Perform | Positive Finding | Significance |
|---|---|---|---|
| Static mechanical allodynia | Apply gentle pressure with finger or blunt probe to painful area | Pain from normally non-painful pressure | Central sensitization; common in postherpetic neuralgia |
| Dynamic mechanical allodynia | Lightly stroke skin with cotton wisp or brush | Pain from light moving touch (often described as burning or stinging) | A-beta fiber-mediated pain; central sensitization; highly specific for neuropathic pain |
| Temporal summation (wind-up) | Apply repeated pinprick at same site at approximately 1 Hz for 30 seconds | Progressive increase in perceived pain intensity with repeated stimuli | Indicates central sensitization; NMDA receptor involvement |
| Cold allodynia | Apply cold stimulus (cold tuning fork, acetone drop) to affected area | Pain from normally tolerable cold | Small fiber sensitization; common in oxaliplatin-induced neuropathy |
| Tinel’s sign | Tap over nerve at common entrapment sites (carpal tunnel, cubital tunnel, fibular head) | Electric shock sensation radiating into nerve distribution | Nerve irritation at that site; suggests entrapment or neuroma |
Motor Examination
Strength Testing (MRC Scale)
- Distal weakness pattern: Foot dorsiflexion (L4-L5, peroneal nerve), toe extension, intrinsic hand muscles — suggests length-dependent or mononeuropathy
- Proximal weakness pattern: Hip flexion, shoulder abduction — suggests myopathy, inflammatory neuropathy, or diabetic amyotrophy
- Focal weakness: Corresponding to single nerve or root — suggests mononeuropathy or radiculopathy
- Facial weakness: In Guillain-Barré syndrome, Bell’s palsy, or infiltrative process
Muscle Bulk and Tone
- Atrophy: Thenar eminence (median nerve), first dorsal interosseous (ulnar nerve), anterior tibialis (peroneal or L5)
- Fasciculations: Visible twitching suggests denervation; also seen in motor neuron disease
- Tone: Usually normal or reduced in neuropathy; increased tone suggests central lesion
Reflex Examination
| Reflex | Root Level | Abnormal Finding | Interpretation |
|---|---|---|---|
| Biceps | C5-C6 | Absent or reduced | C5-C6 radiculopathy; brachial plexopathy; peripheral neuropathy |
| Triceps | C7-C8 | Absent or reduced | C7 radiculopathy; brachial plexopathy |
| Brachioradialis | C5-C6 | Absent or reduced | C5-C6 radiculopathy |
| Knee (patellar) | L3-L4 | Absent or reduced | L3-L4 radiculopathy; femoral neuropathy; peripheral neuropathy |
| Ankle (Achilles) | S1-S2 | Absent or reduced (often earliest reflex lost in length-dependent neuropathy) | S1 radiculopathy; peripheral polyneuropathy; often absent in diabetic neuropathy |
| Plantar response | Corticospinal tract | Extensor (Babinski sign) | Upper motor neuron lesion — suggests central rather than peripheral pathology |
Pattern Recognition: Reflexes in Different Conditions
- Length-dependent polyneuropathy: Ankle reflexes absent first, then knee; upper limb reflexes often preserved
- Guillain-Barré syndrome: Areflexia or hyporeflexia, often generalized early
- Radiculopathy: Single reflex affected corresponding to involved root
- Small fiber neuropathy: Reflexes typically preserved (large fibers intact)
Autonomic Examination
| Test | How to Assess | Abnormal Finding | Associated Conditions |
|---|---|---|---|
| Orthostatic blood pressure | Measure BP supine, then standing at 1 and 3 minutes | Drop ≥20/10 mmHg without compensatory heart rate increase | Diabetic autonomic neuropathy, amyloidosis, pure autonomic failure |
| Skin examination | Inspect for sweating patterns, skin color, temperature, trophic changes | Anhidrosis (dry skin), color changes, cool extremities, hair loss, shiny skin | Small fiber neuropathy with autonomic involvement |
| Pupillary responses | Test pupil reactivity to light and accommodation | Sluggish or absent responses; Horner syndrome | Autonomic neuropathy; Adie’s pupil in Holmes-Adie syndrome |
| Sudomotor function | Observe sweating; specialized testing (QSART) if available | Reduced or absent sweating in affected areas | Small fiber/autonomic neuropathy |
Specific Examination Maneuvers by Suspected Condition
| Condition | Examination Maneuver | Positive Finding |
|---|---|---|
| Carpal tunnel syndrome | Phalen’s test (wrist flexion for 60 seconds); Tinel’s sign at wrist; thenar muscle inspection | Paresthesias in median nerve distribution; thenar atrophy in advanced cases |
| Ulnar neuropathy | Tinel’s sign at elbow; Froment’s sign (thumb flexion compensating for weak adductor) | Tingling in ulnar distribution; weakness of finger abduction; “claw hand” in severe cases |
| Cervical radiculopathy | Spurling’s test (neck extension with rotation and axial compression) | Reproduction of radicular arm pain |
| Lumbar radiculopathy | Straight leg raise (L5-S1); femoral stretch test (L2-L4) | Reproduction of radicular leg pain at less than 60 degrees (SLR) |
| Trigeminal neuralgia | Test sensation in V1, V2, V3 divisions; corneal reflex; palpate trigger zones | Trigger zones that precipitate attacks; sensory loss suggests secondary cause |
| Meralgia paresthetica | Palpate lateral femoral cutaneous nerve at inguinal ligament; test sensation on anterolateral thigh | Tenderness at inguinal ligament; sensory loss over anterolateral thigh without motor findings |
Expected Findings by Etiology
| Condition | Sensory Findings | Motor Findings | Reflexes | Other |
|---|---|---|---|---|
| Diabetic polyneuropathy | Stocking-glove loss; often small fiber first (pinprick, temperature) | Distal weakness late; intrinsic foot muscle wasting | Ankle reflexes absent early | Autonomic signs; foot ulcers; Charcot arthropathy |
| Postherpetic neuralgia | Dermatomal; allodynia prominent; mixed hypo/hyperesthesia | Usually normal | Normal | Scarring from prior rash; pigmentation changes |
| Trigeminal neuralgia | Usually normal between attacks; trigger zones | Normal (weakness suggests secondary cause) | Normal corneal reflex (absent suggests secondary) | Sensory loss is red flag for tumor |
| Carpal tunnel syndrome | Median nerve distribution (thumb, index, middle, radial half ring finger) | Thenar weakness and atrophy in advanced cases | Normal | Phalen’s and Tinel’s positive |
| Radiculopathy | Dermatomal pattern | Myotomal weakness | Single reflex may be reduced | Positive straight leg raise or Spurling’s |
| Small fiber neuropathy | Pinprick and temperature loss; light touch and vibration preserved | Normal strength | Normal or preserved | Autonomic symptoms; normal nerve conduction studies |
| Guillain-Barré syndrome | Variable; often mild sensory symptoms despite weakness | Ascending weakness; facial weakness common | Areflexia | Respiratory monitoring essential; autonomic instability |
Important Teaching Point
Normal examination is common in neuropathic pain! Many patients with significant neuropathic pain have subtle or even normal findings on routine neurological examination. This is particularly true for:
- Small fiber neuropathy: Pinprick and temperature may be difficult to quantify; vibration, proprioception, strength, and reflexes are preserved
- Early diabetic neuropathy: Symptoms often precede detectable examination findings
- Trigeminal neuralgia: Examination is typically normal between attacks
- Central neuropathic pain: May have no sensory loss despite severe pain
A normal examination does not exclude significant neuropathic pain. The history remains paramount, and specialized testing (nerve conduction studies, skin biopsy, quantitative sensory testing) may be needed to confirm the diagnosis.
5. Differential Diagnosis
Systematic approach organized by probability, pattern, and clinical features
Step-by-Step Approach to Neuropathic Pain Differential:
- Step 1: Confirm the pain is neuropathic — use screening tools (DN4 ≥4), identify characteristic descriptors (burning, shooting, electric), look for sensory signs
- Step 2: Localize the lesion — peripheral versus central; if peripheral: polyneuropathy, mononeuropathy, radiculopathy, or plexopathy
- Step 3: Identify the distribution pattern — length-dependent, dermatomal, single nerve, multifocal, or hemibody
- Step 4: Consider the “Big Five” first — diabetic polyneuropathy, postherpetic neuralgia, radiculopathy, chemotherapy-induced, trigeminal neuralgia
- Step 5: If not explained by common causes, systematically evaluate for less common etiologies
Peripheral Polyneuropathy (Length-Dependent Pattern)
| Probability | Condition | Key Features | Distinguishing Clues |
|---|---|---|---|
| COMMON (approximately 60%) | Diabetic polyneuropathy | Symmetric stocking-glove; burning feet worse at night; associated autonomic symptoms | Known diabetes or prediabetes; HbA1c elevated; may have retinopathy, nephropathy |
| COMMON | Idiopathic small fiber neuropathy | Burning pain, preserved reflexes and strength; normal nerve conduction studies | No identifiable cause after workup; skin biopsy confirms reduced intraepidermal nerve fiber density |
| COMMON | Alcoholic neuropathy | Painful, length-dependent; associated nutritional deficiencies | Significant alcohol history; thiamine deficiency; may have liver disease stigmata |
| LESS COMMON (approximately 25%) | Chemotherapy-induced peripheral neuropathy | Onset during or after chemotherapy; dose-dependent; may be predominantly sensory | Platinum compounds, taxanes, vinca alkaloids, bortezomib, thalidomide exposure |
| LESS COMMON | Vitamin B12 deficiency neuropathy | May have combined sensory ataxia and neuropathy; paresthesias | Macrocytic anemia; elevated methylmalonic acid; dietary or absorptive cause |
| LESS COMMON | Chronic inflammatory demyelinating polyneuropathy | Progressive or relapsing; motor and sensory; proximal and distal weakness | Elevated cerebrospinal fluid protein; demyelinating features on nerve conduction studies |
| LESS COMMON | Uremic neuropathy | Length-dependent; restless legs common; associated with chronic kidney disease | Advanced chronic kidney disease (estimated glomerular filtration rate less than 30); improves with dialysis |
| UNCOMMON (approximately 15%) | Hereditary neuropathy (Charcot-Marie-Tooth disease) | Slowly progressive; pes cavus, hammer toes; family history | Onset in childhood or adolescence; high arches; genetic testing confirms |
| UNCOMMON | Amyloid neuropathy | Painful small fiber neuropathy; prominent autonomic features; carpal tunnel syndrome | Cardiac involvement; family history (hereditary); monoclonal protein (AL amyloid) |
| UNCOMMON | Paraneoplastic sensory neuronopathy | Subacute onset; asymmetric; severe sensory ataxia; often painful | Anti-Hu antibodies; associated with small cell lung cancer; may precede cancer diagnosis |
| UNCOMMON | HIV-associated sensory neuropathy | Distal symmetric painful neuropathy; burning feet | HIV positive; may be viral or antiretroviral-related (older nucleoside analogues) |
Focal and Regional Neuropathic Pain
| Probability | Condition | Distribution | Key Features |
|---|---|---|---|
| COMMON | Lumbar radiculopathy | L4, L5, or S1 dermatome; unilateral leg pain | Radiating pain worse with sitting or Valsalva; positive straight leg raise; associated weakness or reflex changes |
| COMMON | Cervical radiculopathy | C5, C6, C7, or C8 dermatome; unilateral arm pain | Radiating arm pain; positive Spurling test; associated weakness or reflex changes |
| COMMON | Postherpetic neuralgia | Dermatomal (thoracic most common, then trigeminal) | History of shingles; allodynia prominent; scarring or pigmentation in affected dermatome |
| COMMON | Carpal tunnel syndrome | Median nerve: thumb, index, middle finger, radial half of ring finger | Nocturnal symptoms; positive Phalen and Tinel tests; thenar atrophy in advanced cases |
| COMMON | Trigeminal neuralgia | V2 and/or V3 divisions most common; unilateral face | Brief electric shock attacks; triggered by touch, chewing, talking; refractory periods between attacks |
| LESS COMMON | Ulnar neuropathy at elbow | Ulnar nerve: little finger, ulnar half of ring finger, medial hand | Elbow flexion worsens symptoms; Tinel at elbow; intrinsic hand muscle weakness |
| LESS COMMON | Meralgia paresthetica | Lateral femoral cutaneous nerve: anterolateral thigh | Pure sensory; no weakness; associated with obesity, tight clothing, pregnancy, diabetes |
| LESS COMMON | Peroneal neuropathy at fibular head | Common peroneal nerve: dorsum of foot, lateral leg | Foot drop; history of leg crossing, weight loss, or compression; sensory loss lateral leg and dorsal foot |
| LESS COMMON | Post-surgical neuropathic pain | Corresponds to surgical incision or nerve territory | Onset after surgery; common after thoracotomy, mastectomy, hernia repair, amputation |
| UNCOMMON | Diabetic lumbosacral radiculoplexus neuropathy (diabetic amyotrophy) | Proximal leg, often unilateral initially; may spread to contralateral | Severe pain preceding weakness; weight loss; often in well-controlled type 2 diabetes |
| UNCOMMON | Neuralgic amyotrophy (Parsonage-Turner syndrome) | Brachial plexus distribution; shoulder and arm | Severe pain at onset followed by weakness; often post-viral or post-surgical; patchy weakness pattern |
Central Neuropathic Pain
| Probability | Condition | Distribution | Key Features |
|---|---|---|---|
| COMMON (among central causes) | Central post-stroke pain | Hemibody or partial hemibody; contralateral to lesion | Onset weeks to months after stroke; thalamic or brainstem lesions; often burning or freezing quality |
| COMMON | Spinal cord injury pain | At-level and/or below-level; may be bilateral | Onset after spinal cord injury; burning, electric, or cramping; associated with sensory loss |
| LESS COMMON | Multiple sclerosis-associated pain | Variable; may include trigeminal neuralgia, Lhermitte’s phenomenon, extremity pain | Known multiple sclerosis or new presentation; may be paroxysmal or continuous; often treatment-resistant |
| UNCOMMON | Syringomyelia | Cape-like distribution (shoulders and upper back); suspended sensory level | Dissociated sensory loss (pain and temperature affected, touch preserved); associated with Chiari malformation |
Anatomical Localization Approach
Peripheral Nerve
Carpal tunnel syndrome
Ulnar neuropathy
Peroneal neuropathy
Meralgia paresthetica
Trigeminal neuralgia
Morton’s neuroma
Nerve Root / Plexus
Cervical radiculopathy
Lumbar radiculopathy
Diabetic amyotrophy
Neuralgic amyotrophy
Thoracic radiculopathy
Cauda equina syndrome
Polyneuropathy
Diabetic polyneuropathy
Alcoholic neuropathy
Chemotherapy-induced
Small fiber neuropathy
B12 deficiency
Chronic inflammatory demyelinating polyneuropathy
Central Nervous System
Central post-stroke pain
Spinal cord injury pain
Multiple sclerosis pain
Syringomyelia
Thalamic pain syndrome
Post-surgical myelopathy
Drug-Induced Neuropathic Pain
| Drug or Drug Class | Mechanism | Characteristics | Time Course |
|---|---|---|---|
| Platinum compounds (cisplatin, oxaliplatin, carboplatin) | Dorsal root ganglion toxicity; DNA adduct formation; mitochondrial dysfunction | Sensory ataxia, painful paresthesias; oxaliplatin causes acute cold-triggered symptoms | Cumulative; may worsen (“coasting”) for months after stopping |
| Taxanes (paclitaxel, docetaxel) | Microtubule disruption; axonal transport impairment | Length-dependent sensory neuropathy; painful paresthesias; myalgias | Dose-dependent; may persist long-term |
| Vinca alkaloids (vincristine) | Microtubule disruption; axonal degeneration | Sensory and motor; autonomic involvement (constipation) | Dose-limiting; often requires dose reduction |
| Bortezomib | Proteasome inhibition; mitochondrial dysfunction | Painful small fiber neuropathy; burning feet | Dose-dependent; may be partially reversible |
| Thalidomide/lenalidomide | Antiangiogenic effects on nerve blood supply; direct neurotoxicity | Length-dependent sensory neuropathy; painful | Cumulative; often irreversible |
| Metronidazole | Unknown; possibly RNA incorporation | Sensory neuropathy after prolonged use (usually greater than 4 weeks cumulative) | Usually reversible if caught early; may persist if prolonged exposure |
| Isoniazid | Pyridoxine (vitamin B6) depletion | Sensory neuropathy, paresthesias; preventable with pyridoxine supplementation | Reversible with pyridoxine; develops over weeks to months |
| Nitrofurantoin | Unknown; associated with renal impairment | Sensory and motor neuropathy; often with chronic use or renal impairment | May be severe and persistent; avoid in renal impairment |
| Fluoroquinolones | Unclear; possible mitochondrial toxicity | Peripheral neuropathy; may be rapid onset; associated with tendinopathy | May be irreversible; FDA black box warning |
| Amiodarone | Phospholipidosis; lysosomal dysfunction | Sensory and motor neuropathy; proximal weakness; tremor | Develops over months to years; may persist after stopping |
| Statins | Unclear; possibly mitochondrial effects (controversial) | Sensory neuropathy; paresthesias (rare but reported) | Usually reversible; causal relationship debated |
| Colchicine | Microtubule disruption | Sensory and motor neuropathy; associated myopathy; especially in renal impairment | Dose-dependent; reversible if stopped early |
Quick Reference: “If You See This, Think This”
| Clinical Clue | Think This First | Next Step |
|---|---|---|
| Burning feet worse at night in a diabetic | Diabetic painful polyneuropathy | Confirm with examination; consider HbA1c, B12, nerve conduction studies |
| Dermatomal pain with history of vesicular rash | Postherpetic neuralgia | Clinical diagnosis; examine for allodynia and scarring |
| Brief electric shocks in face triggered by touch | Trigeminal neuralgia | MRI brain with attention to trigeminal nerve to rule out secondary causes |
| Nocturnal hand numbness relieved by shaking | Carpal tunnel syndrome | Nerve conduction studies; consider ultrasound |
| Radiating leg pain worse with sitting, positive straight leg raise | Lumbar radiculopathy | MRI lumbar spine if red flags, progressive weakness, or refractory to conservative treatment |
| Stocking-glove numbness with normal reflexes and strength | Small fiber neuropathy | Skin biopsy for intraepidermal nerve fiber density; autonomic testing |
| Hemibody pain weeks after stroke | Central post-stroke pain | Confirm thalamic or spinothalamic involvement on imaging; tricyclics or lamotrigine first-line |
| Proximal leg pain and weakness in diabetic with weight loss | Diabetic lumbosacral radiculoplexus neuropathy (diabetic amyotrophy) | EMG/nerve conduction studies; exclude structural lesion with MRI; immunotherapy may help |
| Painful neuropathy with carpal tunnel and cardiac symptoms | Amyloidosis (transthyretin or AL) | Serum and urine protein electrophoresis; cardiac biomarkers; consider tissue biopsy |
| Rapidly progressive asymmetric neuropathy with systemic symptoms | Vasculitic neuropathy | ESR, CRP, ANCA, hepatitis serologies; nerve biopsy; urgent evaluation |
| Neuropathy with high arches and hammer toes since adolescence | Hereditary neuropathy (Charcot-Marie-Tooth disease) | Family history; genetic testing; nerve conduction studies show diffuse slowing |
| Subacute sensory ataxia with pain, known malignancy or smoking | Paraneoplastic sensory neuronopathy | Anti-Hu and paraneoplastic antibody panel; CT chest; cerebrospinal fluid analysis |
Important: Conditions That Mimic Neuropathic Pain
- Peripheral arterial disease: May cause burning pain in feet; check pulses, ankle-brachial index
- Restless legs syndrome: Uncomfortable sensations relieved by movement; often coexists with neuropathy
- Fibromyalgia: Widespread pain with normal neurological examination; nociplastic rather than neuropathic
- Complex regional pain syndrome: Pain with autonomic and trophic changes; may be disproportionate to any precipitating injury
- Myofascial pain: Trigger points, regional pain; may coexist with neuropathic conditions
- Functional neurological disorder: Sensory symptoms not conforming to neuroanatomy; positive signs on examination
6. Diagnostic Investigations
A stepwise, cost-effective approach guided by clinical suspicion
Investigation Principles: The diagnosis of neuropathic pain is primarily clinical, based on history and examination. Investigations serve to: (1) confirm the presence of nervous system lesion, (2) identify the underlying etiology, and (3) guide treatment decisions. A targeted approach based on clinical presentation is more cost-effective than extensive screening panels.
Baseline Investigations for All Patients with Suspected Peripheral Neuropathy
| Investigation | Purpose | What to Look For | Practical Points |
|---|---|---|---|
| Fasting glucose and HbA1c | Screen for diabetes and prediabetes (most common treatable cause) | Fasting glucose ≥126 mg/dL (7.0 mmol/L); HbA1c ≥6.5% diagnostic of diabetes; 5.7-6.4% indicates prediabetes | Prediabetes can cause neuropathy; oral glucose tolerance test may detect impaired glucose tolerance missed by fasting glucose |
| Vitamin B12 level | Screen for B12 deficiency (treatable and common) | Low B12 (less than 200 pg/mL); borderline levels (200-400 pg/mL) may still indicate deficiency | If borderline, check methylmalonic acid (elevated in true B12 deficiency); consider checking folate |
| Complete blood count | Screen for macrocytic anemia (B12/folate), infection, malignancy | Macrocytosis (MCV greater than 100 fL); anemia; abnormal white cell count | Macrocytosis may be absent in B12 deficiency with concurrent iron deficiency or thalassemia trait |
| Basic metabolic panel | Screen for renal dysfunction (uremic neuropathy), electrolyte abnormalities | Elevated creatinine; reduced estimated glomerular filtration rate | Chronic kidney disease stage 4-5 associated with uremic neuropathy; affects drug dosing |
| Thyroid function tests | Screen for hypothyroidism (associated with neuropathy and carpal tunnel) | Elevated TSH; low free T4 | Hypothyroidism is a reversible cause; may present with carpal tunnel syndrome |
| Liver function tests | Screen for liver disease (associated with alcoholic neuropathy, hepatitis C-related) | Elevated transaminases, gamma-glutamyl transferase; evidence of cirrhosis | Consider hepatitis B and C serologies if risk factors or unexplained liver abnormalities |
| Erythrocyte sedimentation rate and C-reactive protein | Screen for inflammatory or vasculitic process | Elevated inflammatory markers | If elevated, consider vasculitis, connective tissue disease, infection, or malignancy |
Electrodiagnostic Studies
Nerve Conduction Studies and Electromyography
Electrodiagnostic studies are the gold standard for confirming and characterizing peripheral neuropathy. They help distinguish:
- Axonal versus demyelinating: Guides differential diagnosis and treatment (demyelinating suggests inflammatory or hereditary causes)
- Sensory versus motor versus mixed: Pure sensory suggests sensory neuronopathy or small fiber neuropathy
- Focal versus generalized: Confirms mononeuropathy, radiculopathy, or polyneuropathy
- Severity: Helps with prognosis and monitoring
Limitations: Normal nerve conduction studies do not exclude neuropathy — small fiber neuropathy affects unmyelinated fibers not tested by standard nerve conduction studies. EMG changes may take 2-3 weeks to develop after acute nerve injury.
| Finding | Pattern | Suggests |
|---|---|---|
| Reduced amplitudes with preserved conduction velocities | Axonal pattern | Diabetic, toxic, metabolic, most common polyneuropathies |
| Slowed conduction velocities with conduction block | Demyelinating pattern | Chronic inflammatory demyelinating polyneuropathy, Guillain-Barré syndrome, Charcot-Marie-Tooth type 1 |
| Focal slowing or conduction block at common entrapment sites | Entrapment neuropathy | Carpal tunnel syndrome, ulnar neuropathy at elbow, peroneal neuropathy at fibular head |
| Asymmetric, patchy abnormalities in multiple nerves | Mononeuritis multiplex | Vasculitis, diabetes, sarcoidosis, leprosy |
| Absent sensory responses with normal motor studies | Sensory neuronopathy pattern | Paraneoplastic, Sjögren syndrome, cisplatin toxicity |
| Normal nerve conduction studies in patient with burning pain | Possible small fiber neuropathy | Proceed to skin biopsy and autonomic testing |
Targeted Investigations by Suspected Etiology
If Suspecting Small Fiber Neuropathy
First-Line Tests
- Skin punch biopsy: Gold standard; intraepidermal nerve fiber density less than 5th percentile for age confirms diagnosis
- Quantitative sudomotor axon reflex testing (QSART): Tests sudomotor (sweat) function; abnormal in small fiber neuropathy with autonomic involvement
- Glucose tolerance test: 2-hour oral glucose tolerance test may reveal impaired glucose tolerance missed by fasting glucose
Second-Line Tests
- Sjögren antibodies (anti-SSA/Ro, anti-SSB/La): Sjögren syndrome is common cause of small fiber neuropathy
- Celiac serologies: Tissue transglutaminase IgA; celiac disease associated with small fiber neuropathy
- Genetic testing: Sodium channel mutations (SCN9A, SCN10A, SCN11A) in familial cases or erythromelalgia phenotype
- Amyloid workup: If autonomic symptoms prominent; serum free light chains, cardiac biomarkers
If Suspecting Inflammatory or Autoimmune Neuropathy
First-Line Tests
- Cerebrospinal fluid analysis: Elevated protein with normal cell count (albuminocytologic dissociation) in chronic inflammatory demyelinating polyneuropathy and Guillain-Barré syndrome
- Serum protein electrophoresis and immunofixation: Screen for monoclonal gammopathy (associated with neuropathy)
- Anti-ganglioside antibodies: Anti-GM1 (multifocal motor neuropathy), anti-GQ1b (Miller Fisher syndrome), anti-MAG (anti-myelin-associated glycoprotein neuropathy)
Second-Line Tests
- MRI of spine or plexus: Nerve root enhancement in inflammatory radiculopathy; plexus abnormalities
- Nerve ultrasound: Increased nerve cross-sectional area in chronic inflammatory demyelinating polyneuropathy and hereditary neuropathies
- Nerve biopsy: Reserved for suspected vasculitis, amyloidosis, or when diagnosis unclear; sural nerve most common site
If Suspecting Vasculitic Neuropathy
First-Line Tests
- ANCA (antineutrophil cytoplasmic antibodies): p-ANCA (microscopic polyangiitis, eosinophilic granulomatosis with polyangiitis), c-ANCA (granulomatosis with polyangiitis)
- Hepatitis B and C serologies: Hepatitis-associated cryoglobulinemic vasculitis
- Cryoglobulins: Cryoglobulinemic vasculitis
- ANA and extractable nuclear antigens: Connective tissue disease-associated vasculitis
Second-Line Tests
- Nerve and muscle biopsy: Definitive diagnosis; shows vasculitis of epineurial vessels with nerve fiber damage
- Angiography: May show beading of medium vessels in polyarteritis nodosa
- Tissue biopsy of other organs: Skin, kidney, or lung depending on systemic involvement
If Suspecting Hereditary Neuropathy
First-Line Tests
- Nerve conduction studies: Uniform slowing suggests Charcot-Marie-Tooth type 1; axonal pattern in Charcot-Marie-Tooth type 2
- Family history and examination of relatives: May reveal undiagnosed affected family members
- Genetic testing: Start with PMP22 duplication (Charcot-Marie-Tooth 1A, most common); then expanded panels
Second-Line Tests
- Whole exome sequencing: If standard genetic panels negative
- Nerve ultrasound: Diffusely enlarged nerves in demyelinating hereditary neuropathies
- Transthyretin gene testing: If amyloid neuropathy suspected (hereditary transthyretin amyloidosis)
If Suspecting Paraneoplastic Neuropathy
First-Line Tests
- Paraneoplastic antibody panel: Anti-Hu (ANNA-1), anti-CV2/CRMP5, anti-amphiphysin
- CT chest, abdomen, pelvis: Screen for occult malignancy (especially small cell lung cancer)
- PET scan: If high suspicion and CT negative
Second-Line Tests
- Cerebrospinal fluid analysis: May show inflammatory changes
- Mammography: In women (anti-Hu associated with breast cancer)
- Testicular ultrasound: In young men with sensory neuronopathy
Imaging Studies
| Imaging Modality | Indication | What to Look For |
|---|---|---|
| MRI spine (cervical or lumbar) | Radiculopathy with red flags, progressive weakness, or refractory to treatment; suspected myelopathy | Disc herniation, foraminal stenosis, spinal cord compression, syringomyelia, tumor |
| MRI brain | Trigeminal neuralgia (rule out secondary causes); central neuropathic pain | Neurovascular compression (trigeminal neuralgia); thalamic lesion (post-stroke pain); multiple sclerosis plaques |
| MRI brachial or lumbosacral plexus | Suspected plexopathy; tumor infiltration; radiation plexopathy | Nerve enlargement, enhancement, mass lesion, radiation changes |
| Nerve ultrasound | Entrapment neuropathies; inflammatory neuropathies; nerve tumors | Nerve swelling at entrapment sites; diffuse enlargement in chronic inflammatory demyelinating polyneuropathy; focal masses |
Empiric Treatment Trials as Diagnostic Tools
When Empiric Trials Help Clarify Diagnosis
In some situations, response to treatment supports a diagnosis or guides further investigation:
- Carbamazepine trial for suspected trigeminal neuralgia: Dramatic response strongly supports diagnosis; lack of response suggests alternative diagnosis or secondary trigeminal neuralgia
- Immunotherapy trial for suspected chronic inflammatory demyelinating polyneuropathy: Response to intravenous immunoglobulin or corticosteroids supports inflammatory etiology (must have supportive electrodiagnostic and cerebrospinal fluid findings)
- Glucose control optimization: Improvement in painful diabetic neuropathy with strict glycemic control supports diabetic etiology
- Vitamin B12 replacement: Clinical improvement after B12 supplementation confirms deficiency as contributory cause
- Medication discontinuation: Improvement after stopping suspected causative drug (such as chemotherapy agent or antibiotic) confirms drug-induced neuropathy
Investigation Algorithm Summary
| Clinical Presentation | First-Line Investigations | Second-Line If Unrevealing |
|---|---|---|
| Symmetric length-dependent polyneuropathy | HbA1c, B12, TSH, basic metabolic panel, liver function tests, complete blood count; nerve conduction studies | Serum protein electrophoresis, hepatitis serologies, HIV (if risk factors), oral glucose tolerance test; if nerve conduction studies normal, skin biopsy for small fiber neuropathy |
| Asymmetric or mononeuritis multiplex pattern | HbA1c, ESR, CRP, ANCA, hepatitis B and C, cryoglobulins, ANA; nerve conduction studies | Nerve biopsy; cerebrospinal fluid; imaging of plexus; consider paraneoplastic antibodies |
| Demyelinating pattern on nerve conduction studies | Cerebrospinal fluid (protein), serum protein electrophoresis, anti-ganglioside antibodies | Genetic testing for Charcot-Marie-Tooth; nerve ultrasound; MRI of plexus/roots |
| Pure sensory with ataxia (neuronopathy pattern) | Paraneoplastic antibodies (anti-Hu), CT chest, Sjögren antibodies | PET scan; cerebrospinal fluid analysis; further malignancy workup |
| Focal neuropathy (single nerve) | Nerve conduction studies localize lesion; ultrasound of nerve | MRI if tumor suspected; surgical exploration if compression not relieved conservatively |
| Radiculopathy | MRI spine (if red flags, progressive, or refractory); EMG if clinical diagnosis unclear | CT myelogram if MRI contraindicated; consider other causes if imaging does not explain symptoms |
7. Pattern Recognition and Clinical Decision-Making
Practical algorithms and decision pathways
Step 1: Is This Urgent?
| Clinical Scenario | Urgency Level | Immediate Action |
|---|---|---|
| Rapidly progressive weakness with respiratory symptoms (Guillain-Barré syndrome) | EMERGENT | Admit to hospital; monitor respiratory function (forced vital capacity); prepare for potential intubation; initiate intravenous immunoglobulin or plasmapheresis |
| Cauda equina syndrome (saddle anesthesia, bladder dysfunction, bilateral leg symptoms) | EMERGENT | Emergent MRI lumbar spine; urgent surgical consultation; decompression within 24-48 hours improves outcomes |
| Acute spinal cord compression (myelopathic signs, sensory level) | EMERGENT | Emergent MRI spine; high-dose corticosteroids if malignant; urgent neurosurgical or oncological intervention |
| Trigeminal neuralgia with sensory loss or other cranial nerve findings | URGENT | MRI brain with trigeminal protocol within days; rule out tumor, multiple sclerosis, or other secondary cause |
| Mononeuritis multiplex with systemic symptoms (fever, weight loss, rash) | URGENT | Urgent vasculitis workup (ANCA, ESR, CRP); consider early nerve biopsy; immunosuppression may be needed promptly |
| Progressive motor neuropathy (foot drop, hand weakness evolving over weeks) | URGENT | Nerve conduction studies within 1-2 weeks; evaluate for treatable causes (chronic inflammatory demyelinating polyneuropathy, multifocal motor neuropathy) |
| Acute herpes zoster (shingles) in patient over 50 | URGENT | Start antiviral therapy within 72 hours of rash onset; consider early pain management to reduce postherpetic neuralgia risk |
| Chronic stable painful polyneuropathy without red flags | ROUTINE | Outpatient workup and management; focus on identifying treatable causes and initiating symptomatic therapy |
| Carpal tunnel syndrome without severe weakness | ROUTINE | Nerve conduction studies to confirm; trial of splinting; consider injection or surgery if refractory |
Step 2: Localize the Lesion
Peripheral Polyneuropathy
Clues: Symmetric, length-dependent (feet before hands), stocking-glove distribution
Action: Proceed to polyneuropathy workup algorithm
Focal Neuropathy
Clues: Single nerve territory, may have motor and sensory findings, entrapment history
Action: Nerve conduction studies to localize; consider ultrasound or MRI
Radiculopathy/Plexopathy
Clues: Dermatomal or plexus distribution, radiating pain, associated weakness
Action: MRI of relevant spine segment or plexus; EMG for confirmation
Mononeuritis Multiplex
Clues: Multiple individual nerves affected, asymmetric, often stepwise progression
Action: Urgent vasculitis workup; consider nerve biopsy
Central Neuropathic Pain
Clues: Hemibody or regional distribution not following peripheral patterns; history of stroke, spinal cord injury, or multiple sclerosis
Action: MRI brain or spine to identify lesion; tricyclics or anticonvulsants first-line
Step 3: Polyneuropathy Workup Algorithm
| Step | Action | If Positive | If Negative |
|---|---|---|---|
| 1. Baseline labs | HbA1c, fasting glucose, B12, TSH, renal function, liver function, CBC | Treat identified cause (diabetes, B12 deficiency, hypothyroidism) | Proceed to Step 2 |
| 2. Nerve conduction studies | Confirm neuropathy; characterize as axonal versus demyelinating | If demyelinating: cerebrospinal fluid, consider chronic inflammatory demyelinating polyneuropathy workup. If axonal: proceed to Step 3 | If normal but symptoms present: consider small fiber neuropathy, proceed to skin biopsy |
| 3. Extended workup | Serum protein electrophoresis, hepatitis B/C, HIV (if risk factors), oral glucose tolerance test, ESR/CRP | Treat identified cause (monoclonal gammopathy workup, hepatitis treatment, glucose control) | Proceed to Step 4 |
| 4. Consider specialized testing | Skin biopsy (small fiber), genetic testing (if hereditary features), paraneoplastic panel (if subacute and atypical), anti-ganglioside antibodies | Diagnosis-specific management | Label as idiopathic; treat symptomatically; consider re-evaluation if progression |
Step 4: First-Line Pharmacotherapy Selection
Evidence-Based First-Line Agents
Guidelines recommend the following as first-line options for neuropathic pain (all have similar efficacy; choice based on patient factors):
- Gabapentinoids: Gabapentin or pregabalin — good for anxiety comorbidity; avoid in patients at risk for misuse
- Serotonin-norepinephrine reuptake inhibitors: Duloxetine or venlafaxine — good for depression/anxiety comorbidity; duloxetine also approved for diabetic neuropathy
- Tricyclic antidepressants: Amitriptyline, nortriptyline — effective and inexpensive; avoid in elderly (anticholinergic effects), cardiac disease, glaucoma
- Topical agents: Lidocaine 5% patch, capsaicin 8% patch — consider for localized neuropathic pain (postherpetic neuralgia, focal neuropathy)
| Clinical Scenario | Preferred First-Line Agent | Rationale |
|---|---|---|
| Painful diabetic polyneuropathy | Duloxetine or pregabalin | Both FDA-approved for this indication; duloxetine preferred if depression comorbidity |
| Postherpetic neuralgia | Gabapentin, pregabalin, or lidocaine 5% patch | Topical lidocaine good for localized allodynia with minimal systemic effects |
| Trigeminal neuralgia | Carbamazepine or oxcarbazepine | Sodium channel blockers are specifically effective for paroxysmal lancinating pain; carbamazepine is first-line |
| Neuropathic pain with comorbid depression or anxiety | Duloxetine or amitriptyline | Dual benefit for mood and pain; serotonin-norepinephrine reuptake inhibitors or tricyclics enhance descending inhibition |
| Neuropathic pain with comorbid insomnia | Amitriptyline, nortriptyline, or pregabalin (evening dosing) | Sedating properties can be therapeutic for sleep; give at bedtime |
| Elderly patient or multiple comorbidities | Gabapentin (start low) or topical lidocaine | Avoid tricyclics (anticholinergic, cardiac effects); duloxetine acceptable but watch for hyponatremia |
| Patient with history of substance use disorder | Duloxetine or tricyclic antidepressant | Avoid gabapentinoids (misuse potential); avoid opioids |
| Central post-stroke pain | Amitriptyline or lamotrigine | Often refractory; lamotrigine has some evidence for central pain; may require combination therapy |
| Localized neuropathic pain (small area) | Lidocaine 5% patch or capsaicin 8% patch | Topical therapy minimizes systemic side effects; capsaicin 8% requires clinic application |
| Chemotherapy-induced peripheral neuropathy | Duloxetine | Only agent with randomized controlled trial evidence for this indication |
“What Do I Do If…” Decision Reference
| Clinical Situation | Immediate Action | Next Step |
|---|---|---|
| First-line agent ineffective after adequate trial (4-8 weeks at therapeutic dose) | Confirm diagnosis is correct; ensure adequate dose reached; assess adherence | Switch to different first-line class OR add second agent from different class (combination therapy) |
| First-line agent causes intolerable side effects | Reduce dose or switch to different agent within same class (for example, nortriptyline instead of amitriptyline) | If class-related side effect, switch to different first-line class |
| Patient has failed multiple first-line agents | Consider combination therapy (gabapentinoid plus antidepressant); reassess diagnosis | Refer to pain specialist or neurologist; consider interventional options (nerve blocks, spinal cord stimulation) |
| Patient requests opioids | Explain that opioids are not first-line for neuropathic pain; discuss evidence for first-line agents | If considering opioids (refractory cases), use tramadol or tapentadol first; establish treatment agreement; use lowest effective dose |
| New neurological deficit develops (weakness, atrophy) | Urgent reassessment; repeat nerve conduction studies | Rule out progressive or treatable cause; consider referral |
| Patient with neuropathy develops foot ulcer | Wound care; assess for infection; offload pressure | Podiatry and vascular surgery referral; optimize glucose control; education on foot care |
| Suspected medication-induced neuropathy | Discontinue or reduce offending agent if possible | Monitor for improvement (may take weeks to months); symptomatic treatment while waiting |
| Neuropathic pain with severe functional impairment | Initiate pharmacotherapy; assess for depression and anxiety | Multidisciplinary approach: physical therapy, occupational therapy, psychology, pain specialist |
Troubleshooting Refractory Neuropathic Pain
Systematic Approach to Treatment Failure
- Is the diagnosis correct? Reconsider differential; could this be nociplastic pain (fibromyalgia), vascular, or musculoskeletal?
- Was the treatment adequate? Was therapeutic dose reached? Was duration sufficient (at least 4-8 weeks)?
- Is the patient adherent? Side effects causing non-adherence? Understanding of treatment goals?
- Are there untreated comorbidities? Depression, anxiety, and sleep disorders amplify pain; treat these concurrently
- Is there an ongoing cause? Continued exposure to neurotoxin? Uncontrolled diabetes? Progression of underlying disease?
- Are expectations realistic? Complete pain relief is uncommon; goal is meaningful reduction (30-50%) and improved function
- Has combination therapy been tried? Evidence supports combining agents from different classes
- Have interventional options been considered? Nerve blocks, spinal cord stimulation, dorsal root ganglion stimulation for appropriate candidates
When to Refer
| Refer To | Indications |
|---|---|
| Neurologist | Diagnostic uncertainty; atypical presentation; suspected inflammatory, hereditary, or paraneoplastic neuropathy; progressive weakness; need for specialized testing |
| Pain specialist | Refractory to multiple first-line agents; candidate for interventional procedures; complex pain management needs; opioid management |
| Neurosurgeon | Trigeminal neuralgia refractory to medications; spinal cord stimulator candidate; structural lesion requiring surgery |
| Rheumatologist | Suspected vasculitic neuropathy; connective tissue disease-associated neuropathy |
| Physiatrist (Physical Medicine and Rehabilitation) | Functional rehabilitation; comprehensive pain management; electrodiagnostic expertise |
| Psychiatry or Psychology | Significant comorbid depression or anxiety; chronic pain coping strategies; cognitive behavioral therapy for pain |
8. Clinical Pearls and Pitfalls
Practical wisdom — learn from successes and avoid common mistakes
Must-Know Clinical Pearls
Neuropathic pain descriptors are diagnostic: Burning, shooting, electric shock-like, and tingling are highly suggestive. Use screening tools like DN4 (score ≥4) to support the diagnosis when history is ambiguous.
Small fiber neuropathy explains “normal workup” patients: If a patient has classic neuropathic symptoms but normal nerve conduction studies, reflexes, and strength, think small fiber neuropathy. Skin biopsy is the gold standard for diagnosis.
Prediabetes causes neuropathy: Do not dismiss impaired glucose tolerance. An oral glucose tolerance test can reveal prediabetes missed by fasting glucose or HbA1c, and this is a common cause of otherwise idiopathic neuropathy.
Trigeminal neuralgia responds dramatically to carbamazepine: A robust response to carbamazepine strongly supports the diagnosis. Lack of response should prompt reconsideration of the diagnosis or investigation for secondary causes.
Combination therapy works: When monotherapy fails, combining agents from different classes (for example, gabapentinoid plus serotonin-norepinephrine reuptake inhibitor) often provides better relief than switching between monotherapies.
Topical therapy is underutilized: Lidocaine 5% patches and capsaicin 8% patches are effective for localized neuropathic pain with minimal systemic side effects. Consider these first-line for focal conditions like postherpetic neuralgia.
Treat comorbidities aggressively: Depression, anxiety, and sleep disturbance amplify pain perception and impair treatment response. Addressing these is as important as targeting the pain itself.
Set realistic expectations: Complete pain relief is rare in chronic neuropathic pain. A 30-50% reduction in pain intensity with improved function is a realistic and meaningful goal. Communicate this early to avoid frustration.
Critical Pitfalls to Avoid
Assuming normal nerve conduction studies exclude neuropathy: Small fiber neuropathy affects unmyelinated C fibers and thinly myelinated A-delta fibers not tested by standard nerve conduction studies. A normal study in a patient with burning pain and autonomic symptoms should prompt skin biopsy.
Missing sensory loss in trigeminal neuralgia: Classic trigeminal neuralgia has no sensory loss between attacks. If sensory loss is present, investigate for tumor, multiple sclerosis, or other secondary cause with MRI.
Giving up on medications too quickly: Many first-line agents require 4-8 weeks at therapeutic doses to show full effect. Titrate to target dose and allow adequate time before concluding treatment failure.
Using opioids as first-line therapy: Opioids have limited efficacy in neuropathic pain, carry significant risks (tolerance, dependence, hyperalgesia), and are not recommended as first-line. Reserve for refractory cases under specialist guidance.
Overlooking medication-induced neuropathy: Always review the medication list. Chemotherapy, antibiotics (metronidazole, fluoroquinolones), and other drugs cause neuropathy. Stopping the offending agent may be the most important intervention.
Ignoring autonomic symptoms: Orthostatic hypotension, gastroparesis, urinary dysfunction, and sweating abnormalities suggest autonomic involvement and may indicate more serious conditions (diabetic autonomic neuropathy, amyloidosis).
Attributing all foot pain in diabetics to neuropathy: Peripheral arterial disease, musculoskeletal conditions, and infection can coexist with diabetic neuropathy. Always check pulses and consider alternative or additional diagnoses.
Failing to recognize Guillain-Barré syndrome: Ascending weakness with areflexia following infection requires urgent evaluation. Respiratory failure can develop rapidly. Monitor forced vital capacity and consider early treatment with intravenous immunoglobulin or plasmapheresis.
Key Takeaways
- Neuropathic pain is defined by pain arising from a lesion or disease of the somatosensory nervous system — not simply pain in a nerve distribution.
- The “Big Five” causes (diabetic polyneuropathy, postherpetic neuralgia, radiculopathy, chemotherapy-induced neuropathy, trigeminal neuralgia) account for the majority of cases.
- The diagnosis is primarily clinical — characteristic descriptors (burning, shooting, electric), distribution pattern, and associated sensory signs guide diagnosis.
- Localization (polyneuropathy, mononeuropathy, radiculopathy, central) determines the differential diagnosis and investigation approach.
- Baseline workup for polyneuropathy includes HbA1c, vitamin B12, complete blood count, metabolic panel, and thyroid function; nerve conduction studies characterize the neuropathy.
- Normal nerve conduction studies do not exclude neuropathy — small fiber neuropathy requires skin biopsy for diagnosis.
- First-line pharmacotherapy includes gabapentinoids, serotonin-norepinephrine reuptake inhibitors, tricyclic antidepressants, and topical agents — choice based on patient factors and comorbidities.
- Carbamazepine is specifically first-line for trigeminal neuralgia; other neuropathic pain conditions respond to the general first-line agents.
- Treatment goals should be realistic — 30-50% pain reduction with improved function rather than complete pain elimination.
- Combination therapy and multimodal approaches (pharmacotherapy, physical therapy, psychology) improve outcomes in refractory cases.
- Red flags (rapid progression, weakness, autonomic symptoms, systemic features) require urgent evaluation to rule out treatable or dangerous causes.
- Address modifiable causes: optimize glucose control, replace vitamin B12, stop offending medications, treat underlying inflammation.
Quick Reference Algorithm
Systematic Approach to Neuropathic Pain:
- Confirm neuropathic pain: Use characteristic descriptors and screening tools (DN4 ≥4); distinguish from nociceptive and nociplastic pain
- Assess for red flags: Rapid progression, weakness, bowel/bladder dysfunction, systemic symptoms — urgent evaluation if present
- Localize the lesion: Polyneuropathy (length-dependent), focal neuropathy (single nerve), radiculopathy (dermatomal), plexopathy, or central
- Characterize the pattern: Axonal versus demyelinating; small fiber versus large fiber; sensory versus sensorimotor
- Identify the etiology: Baseline labs for all; targeted investigations based on clinical pattern; treat reversible causes
- Initiate first-line therapy: Select based on patient factors — gabapentinoid, serotonin-norepinephrine reuptake inhibitor, tricyclic antidepressant, or topical agent
- Titrate to therapeutic dose: Allow 4-8 weeks for full effect; monitor for side effects and adjust accordingly
- Reassess and adjust: If inadequate response, consider combination therapy, alternative agents, or referral for interventional options
- Address the whole patient: Treat comorbid depression, anxiety, and sleep disturbance; set realistic expectations; consider multidisciplinary care