Clinical Approach to Focal Neurologic Deficit
Comprehensive Practical Framework1. Symptom Overview
Understanding the clinical significance and classification of focal neurologic deficit
Focal neurologic deficits represent one of the most critical presentations in medicine, demanding rapid assessment and intervention. Stroke alone affects approximately 795,000 people annually in the United States, with ischemic stroke accounting for 87% of cases. Neurologic emergencies constitute approximately 10-15% of all emergency department visits, and the time-sensitive nature of many causes—particularly acute ischemic stroke where “time is brain”—makes rapid recognition and localization essential. Beyond stroke, focal deficits may herald brain tumors, multiple sclerosis, infections, or other conditions requiring urgent diagnosis.
Definition
A focal neurologic deficit is an abnormality of nervous system function that can be localized to a specific anatomical structure or region of the nervous system. Unlike diffuse or global dysfunction (such as delirium or coma), focal deficits point to discrete lesions affecting the brain, spinal cord, nerve roots, peripheral nerves, neuromuscular junction, or muscles. The deficit may manifest as weakness, sensory loss, visual disturbance, speech impairment, coordination problems, or cranial nerve dysfunction.
Classification by Temporal Profile
| Category | Onset and Duration | Common Causes | Clinical Significance |
|---|---|---|---|
| Hyperacute | Seconds to minutes; maximal at onset | Ischemic stroke, hemorrhagic stroke, seizure with Todd’s paralysis | Vascular emergency until proven otherwise; activate stroke protocols immediately |
| Acute | Hours to days; progressive or stepwise | Evolving stroke, encephalitis, acute demyelination, abscess | Urgent evaluation required; may still be within treatment windows |
| Subacute | Days to weeks; gradual progression | Brain tumor, subdural hematoma, progressive infection, inflammatory conditions | Suggests mass lesion or inflammatory process; imaging essential |
| Chronic | Weeks to months; slow progression | Slow-growing tumor, degenerative disease, chronic infection | Allows time for comprehensive workup; still requires definitive diagnosis |
| Transient | Minutes to hours; complete resolution | Transient ischemic attack, migraine aura, seizure, hypoglycemia | High-risk warning sign; transient ischemic attack carries 10-15% 90-day stroke risk |
Classification by Anatomical Localization
Central Nervous System Lesions
Cortical: Higher function deficits (aphasia, neglect, apraxia) plus contralateral motor/sensory findings; seizures common
Subcortical (white matter/basal ganglia): Pure motor or sensory deficits without cortical signs; movement disorders
Brainstem: Crossed deficits (ipsilateral cranial nerve, contralateral body); vertigo, diplopia, dysarthria, dysphagia
Cerebellar: Ipsilateral ataxia, dysmetria, intention tremor; no weakness
Spinal cord: Motor and sensory level; bladder/bowel dysfunction; bilateral findings below lesion
Peripheral Nervous System Lesions
Nerve root (radiculopathy): Dermatomal sensory loss, myotomal weakness, diminished reflexes
Plexus: Multiple nerve root distributions; complex patterns
Peripheral nerve: Specific nerve territory; may be mononeuropathy or polyneuropathy
Neuromuscular junction: Fatigable weakness; no sensory loss; ptosis and diplopia common
Muscle: Proximal weakness typically; no sensory loss; preserved reflexes early
Classification by Type of Deficit
| Deficit Type | Clinical Features | Localizing Value |
|---|---|---|
| Motor weakness | Hemiparesis, monoparesis, paraparesis, quadriparesis; upper versus lower motor neuron patterns | Distribution and pattern narrow localization significantly |
| Sensory disturbance | Numbness, paresthesias, pain; may involve all modalities or be dissociated | Dermatomal, peripheral nerve, hemisensory, or sensory level patterns |
| Visual disturbance | Monocular versus binocular; visual field defects; diplopia | Precisely localizes along visual pathway from eye to occipital cortex |
| Speech and language | Aphasia (language), dysarthria (articulation), apraxia of speech | Aphasia localizes to dominant hemisphere; dysarthria less specific |
| Coordination/gait | Ataxia, dysmetria, dysdiadochokinesia, gait instability | Cerebellar, sensory ataxia, or vestibular localization |
| Cranial nerve dysfunction | Specific patterns based on nerve involved | Highly localizing; especially valuable for brainstem lesions |
The Critical First Question: In any patient presenting with a new focal neurologic deficit, the first priority is determining whether this represents an acute stroke. The phrase “time is brain” reflects that approximately 1.9 million neurons die every minute during an untreated large vessel ischemic stroke. Thrombolytic therapy must be given within 4.5 hours of symptom onset (and earlier is better), while mechanical thrombectomy may extend the window to 24 hours in selected patients. Therefore, rapid recognition and activation of stroke protocols is paramount.
Localization Principle
The pattern of neurologic deficits allows precise anatomical localization before any imaging is obtained. A single lesion should explain all findings—if it cannot, consider multifocal disease (such as multiple sclerosis, metastases, or vasculitis) or a systemic process. Mastering neuroanatomy transforms a seemingly complex presentation into a logical diagnostic puzzle.
2. Pathophysiology and Mechanisms
Understanding the underlying mechanisms of focal neurologic deficit
Understanding the mechanisms by which different pathological processes produce focal neurologic deficits is essential for both accurate diagnosis and appropriate treatment selection. The nervous system is exquisitely sensitive to disruption, and deficits arise when neurons or their connections are damaged, compressed, demyelinated, or deprived of metabolic substrates. The temporal profile of symptom onset often reflects the underlying pathophysiology.
Primary Mechanisms of Neuronal Dysfunction
| Mechanism | Pathophysiology | Typical Onset | Examples |
|---|---|---|---|
| Ischemia | Interruption of blood supply leads to ATP depletion, ionic pump failure, excitotoxicity, and cell death within minutes | Seconds to minutes; maximal at onset or rapidly progressive | Ischemic stroke, transient ischemic attack, hypotensive watershed infarcts |
| Hemorrhage | Direct tissue destruction plus mass effect; blood products are neurotoxic; surrounding edema develops | Seconds to minutes; may progress over hours as hematoma expands | Intracerebral hemorrhage, subarachnoid hemorrhage, subdural hematoma |
| Compression | Mass effect disrupts axonal conduction and blood flow; may cause herniation | Hours to weeks depending on growth rate | Brain tumor, abscess, subdural hematoma, spinal cord compression |
| Demyelination | Loss of myelin sheath slows or blocks action potential conduction; initially reversible | Hours to days; may wax and wane | Multiple sclerosis, acute disseminated encephalomyelitis, Guillain-Barré syndrome |
| Inflammation | Immune-mediated injury, edema, blood-brain barrier disruption | Days to weeks; often subacute | Encephalitis, cerebral vasculitis, neurosarcoidosis |
| Metabolic/Toxic | Neuronal dysfunction from substrate deficiency or toxin accumulation | Variable; often reversible if corrected | Hypoglycemia, hepatic encephalopathy, Wernicke encephalopathy |
| Seizure | Abnormal synchronized neuronal discharge; post-ictal depression follows | Seconds (ictal); minutes to hours (post-ictal Todd’s paralysis) | Focal seizure with motor symptoms, Todd’s paralysis |
The Ischemic Cascade: A Detailed Look
Ischemic stroke provides a paradigm for understanding acute neuronal injury. When blood flow drops below the critical threshold of approximately 10-12 mL/100g/minute, neurons begin to fail within seconds.
| Phase | Timeframe | Pathophysiology | Clinical Implication |
|---|---|---|---|
| Energy failure | Seconds | ATP depletion causes Na+/K+-ATPase failure; neurons depolarize | Immediate symptom onset; potentially reversible if flow restored |
| Excitotoxicity | Minutes | Glutamate release causes calcium influx, activating destructive enzymes | Damage begins spreading; ischemic penumbra at risk |
| Oxidative stress | Minutes to hours | Free radical production damages membranes, proteins, DNA | Reperfusion may paradoxically worsen injury |
| Inflammation | Hours to days | Microglia activation, blood-brain barrier breakdown, leukocyte infiltration | Secondary injury expands lesion; target for future therapies |
| Apoptosis | Hours to days | Programmed cell death in penumbral tissue | Delayed neuronal loss may be preventable |
The Ischemic Penumbra: Surrounding the core of irreversibly damaged tissue is the “ischemic penumbra”—tissue that is dysfunctional but potentially salvageable. This penumbra receives marginal blood flow (typically 12-22 mL/100g/minute) and can survive for hours if reperfusion is achieved. Modern stroke imaging (CT or MRI perfusion) identifies the penumbra to select patients who may benefit from intervention even outside traditional time windows.
Upper Motor Neuron vs Lower Motor Neuron Lesions
The distinction between upper motor neuron (UMN) and lower motor neuron (LMN) patterns is fundamental to localizing motor deficits.
Upper Motor Neuron Pattern
Lesion location: Motor cortex, internal capsule, brainstem, or spinal cord (corticospinal tract)
Weakness pattern: Pyramidal distribution—arm flexors weaker than extensors; leg extensors weaker than flexors
Tone: Increased (spasticity); clasp-knife quality
Reflexes: Hyperreflexia; positive Babinski sign (upgoing toe)
Atrophy: Minimal (disuse atrophy only)
Fasciculations: Absent
Lower Motor Neuron Pattern
Lesion location: Anterior horn cell, nerve root, plexus, peripheral nerve
Weakness pattern: Specific to affected nerve root or peripheral nerve territory
Tone: Decreased (flaccidity)
Reflexes: Hyporeflexia or areflexia
Atrophy: Prominent and early; denervation atrophy
Fasciculations: May be present (anterior horn cell disease)
Vascular Territory Patterns
Each major cerebral artery supplies a defined territory, producing characteristic clinical syndromes when occluded.
| Artery | Territory Supplied | Classic Deficit Pattern |
|---|---|---|
| Middle cerebral artery | Lateral frontal, parietal, temporal cortex; internal capsule; basal ganglia | Contralateral hemiparesis (face and arm greater than leg); hemisensory loss; homonymous hemianopia; aphasia (dominant hemisphere) or neglect (non-dominant) |
| Anterior cerebral artery | Medial frontal and parietal cortex | Contralateral leg weakness greater than arm; abulia; urinary incontinence; grasp reflex |
| Posterior cerebral artery | Occipital lobe; medial temporal lobe; thalamus | Contralateral homonymous hemianopia with macular sparing; memory impairment; thalamic sensory loss |
| Basilar artery | Brainstem; cerebellum | Crossed deficits; quadriparesis; “locked-in syndrome”; coma; cerebellar signs |
| Posterior inferior cerebellar artery (lateral medullary syndrome) | Lateral medulla | Ipsilateral facial sensory loss, Horner syndrome, ataxia, dysarthria, dysphagia; contralateral body pain/temperature loss |
How Specific Conditions Cause Focal Deficits
| Condition | Mechanism | Why This Matters for Diagnosis |
|---|---|---|
| Ischemic stroke | Thrombotic or embolic arterial occlusion causes downstream ischemia; symptoms maximal at onset or rapidly progressive | Hyperacute onset is classic; lacunar strokes from small vessel disease produce pure motor or sensory syndromes |
| Intracerebral hemorrhage | Rupture of small penetrating arteries (often from hypertension); hematoma expands causing mass effect | Often presents with headache and progressive deficits; may be indistinguishable from ischemic stroke clinically |
| Brain tumor | Mass effect, infiltration of neural tissue, surrounding edema, and disruption of blood supply | Subacute progressive course; seizures common; symptoms may fluctuate with edema |
| Multiple sclerosis | Autoimmune demyelination blocks conduction; inflammation causes reversible dysfunction | Episodes lasting days to weeks; may improve spontaneously; dissemination in space and time |
| Brain abscess | Focal infection creates expanding mass with surrounding edema and inflammation | Subacute course with fever and focal signs; may have predisposing factors (endocarditis, sinusitis) |
| Subdural hematoma | Venous bleeding accumulates between dura and arachnoid; gradual compression of brain | Chronic presentation in elderly may have minimal or forgotten trauma; fluctuating symptoms common |
| Migraine with aura | Cortical spreading depression causes transient neuronal dysfunction without ischemia | Gradual “march” of symptoms over 20-60 minutes; complete resolution; history of similar episodes |
Often Overlooked Mechanism: Hypoglycemia
Hypoglycemia is a great mimicker of stroke and should be excluded immediately in any patient with acute focal neurologic deficit. The brain depends almost exclusively on glucose for energy, and hypoglycemia can produce hemiparesis, aphasia, or other focal findings that completely resolve with glucose administration. Always check fingerstick glucose before or simultaneously with stroke code activation—treating hypoglycemia takes seconds and may be curative, while missing it leads to irreversible brain injury.
Transient Ischemic Attack: A Warning Sign
Transient ischemic attack (TIA) represents temporary ischemia without infarction—symptoms resolve completely, typically within 1 hour. However, TIA is a neurologic emergency because it signals high short-term stroke risk. The ABCD2 score helps stratify risk, but approximately 10-15% of TIA patients will have a stroke within 90 days, with the highest risk in the first 48 hours. Urgent evaluation and intervention (antiplatelet therapy, blood pressure control, statin, carotid imaging) can dramatically reduce this risk.
3. History Taking
A comprehensive approach to eliciting the focal neurologic deficit history
Red Flags — Require Emergent Evaluation
- Sudden onset (“thunderclap”) — Stroke, subarachnoid hemorrhage
- Rapid progression over minutes to hours — Expanding hemorrhage, basilar artery occlusion
- Decreased level of consciousness — Mass effect, herniation, brainstem involvement
- Severe headache with focal signs — Hemorrhagic stroke, venous sinus thrombosis
- Neck stiffness with fever — Meningitis, brain abscess
- Bilateral weakness or sensory level — Spinal cord compression (surgical emergency)
- Bladder or bowel dysfunction with leg weakness — Cauda equina syndrome
- New deficit in anticoagulated patient — Intracranial hemorrhage
- Symptoms occurring during Valsalva or exertion — Subarachnoid hemorrhage, cerebral venous thrombosis
- Recent head or neck trauma — Arterial dissection, traumatic hemorrhage
The Most Important Question: “When was the patient last known to be at their neurologic baseline?” This “last known well” time determines eligibility for thrombolysis and thrombectomy. If the patient woke up with symptoms, the last known well time is when they went to sleep—not when they woke up. Document this precisely (date and time) before anything else.
Systematic History: The “FOCAL” Approach
Use the mnemonic “FOCAL” to ensure comprehensive history taking for neurologic deficits:
- F — First moment and Features: Exact time of onset; what were they doing? Was onset sudden (seconds), rapid (minutes), or gradual (hours to days)? What was the first symptom noticed?
- O — Other symptoms and Onset pattern: Associated symptoms (headache, seizure, fever, neck pain, vertigo, nausea, visual changes)? Have symptoms been stable, progressing, fluctuating, or improving?
- C — Characterize the deficit: Precisely what functions are affected? Weakness, numbness, vision, speech, coordination, cognition? Which side? Face, arm, leg—all equally or one more than others?
- A — Antecedents and risk factors: Recent infections, trauma, procedures? Vascular risk factors (hypertension, diabetes, smoking, hyperlipidemia, atrial fibrillation)? Prior strokes or transient ischemic attacks?
- L — Life impact and Limitations: Functional impact? Can they walk, speak, swallow, see? Any similar prior episodes? Baseline functional status?
Targeted Questions by Suspected Cause
| Suspected Cause | Key Features | Ask This Question |
|---|---|---|
| Ischemic stroke | Sudden onset, maximal at start, vascular risk factors, atrial fibrillation | “Exactly what time did this start? What were you doing at that moment? Do you have an irregular heartbeat or take blood thinners?” |
| Hemorrhagic stroke | Severe headache, nausea/vomiting, hypertension, anticoagulation | “Did you have a sudden severe headache when this started? Are you on any blood thinners including aspirin? What is your usual blood pressure?” |
| Transient ischemic attack | Complete resolution, typically within 1 hour, high recurrence risk | “Have your symptoms completely resolved? How long did they last? Have you had any similar brief episodes before?” |
| Subarachnoid hemorrhage | Thunderclap headache, worst headache of life, exertional onset | “Was this the worst headache of your life? Did it come on instantly like a thunderclap? Were you straining, lifting, or having sex when it started?” |
| Brain tumor | Progressive course over weeks, seizures, morning headache, personality change | “Have your symptoms been gradually worsening? Do you have headaches that are worse in the morning? Have you had any seizures or noticed personality changes?” |
| Multiple sclerosis | Young adult, prior episodes, symptoms in different locations at different times | “Have you ever had episodes of visual loss, numbness, or weakness that came and went? Any problems with bladder control or fatigue?” |
| Arterial dissection | Neck pain, recent trauma or manipulation, young patient, Horner syndrome | “Have you had any neck pain or headache? Any recent neck injury, chiropractic manipulation, or even minor trauma like a roller coaster ride?” |
| Seizure with Todd’s paralysis | Witnessed convulsion, post-ictal confusion, gradual resolution | “Did anyone witness shaking or convulsive movements? Did you bite your tongue or lose bladder control? Were you confused afterward?” |
| Migraine with aura | Gradual onset, visual symptoms first, headache follows, prior similar episodes | “Did your symptoms develop gradually over 20-30 minutes? Did you have visual disturbance before the weakness? Do you have a history of migraines?” |
| Subdural hematoma | Elderly, anticoagulation, fluctuating symptoms, often forgotten trauma | “Have you had any falls or head injuries, even minor ones, in the past few weeks? Have your symptoms been coming and going?” |
| Brain abscess or encephalitis | Fever, subacute course, immunocompromise, recent infection | “Have you had any fevers or chills? Any recent infections—ear, sinus, dental? Do you have any conditions affecting your immune system?” |
| Spinal cord compression | Bilateral leg weakness, sensory level, bladder/bowel dysfunction, back pain | “Do you have weakness in both legs? Any back pain? Problems urinating or having bowel movements? Any numbness below a certain level on your body?” |
Vascular Risk Factor Assessment
Essential Vascular History
For any patient with suspected cerebrovascular disease, systematically assess:
- Hypertension: Duration, control, medications, compliance
- Diabetes mellitus: Type, duration, control (hemoglobin A1c), complications
- Hyperlipidemia: Known? Treated? Last lipid panel?
- Atrial fibrillation: Known? Paroxysmal? On anticoagulation?
- Smoking: Current, former, pack-years
- Cardiac disease: Prior myocardial infarction, heart failure, valvular disease, recent procedures
- Prior stroke or transient ischemic attack: When? Workup? Treatment?
- Family history: Stroke, early cardiovascular disease
- Hypercoagulable states: Prior deep venous thrombosis or pulmonary embolism, recurrent pregnancy loss
Medication and Substance History
Medications That Increase Bleeding Risk
- Anticoagulants: Warfarin, direct oral anticoagulants (apixaban, rivaroxaban, dabigatran, edoxaban), heparin — contraindicate thrombolysis, increase hemorrhage risk
- Antiplatelet agents: Aspirin, clopidogrel, ticagrelor, prasugrel — relative contraindication to thrombolysis if dual therapy
- Thrombolytics: Recent tissue plasminogen activator use — absolute contraindication to repeat dosing
Medications That May Cause Focal Deficits
- Insulin and sulfonylureas: Hypoglycemia mimics stroke
- Antihypertensives: Excessive lowering may cause watershed infarcts
- Chemotherapy: Some agents are neurotoxic or increase thrombosis risk
Substances and Focal Deficits
- Cocaine and amphetamines: Vasospasm, hemorrhagic stroke, ischemic stroke
- Alcohol: Intoxication may mask deficits; chronic use increases hemorrhage risk; withdrawal seizures
- Intravenous drug use: Endocarditis with septic emboli, infectious mycotic aneurysms
- Oral contraceptives: Increased stroke risk, especially with smoking or migraine with aura
Recent Procedures
- Cardiac catheterization: Embolic stroke risk
- Carotid surgery or stenting: Hyperperfusion syndrome, embolism
- Any recent surgery: Paradoxical embolism via patent foramen ovale
Social and Functional History
| Domain | Why It Matters | Key Questions |
|---|---|---|
| Baseline functional status | Determines treatment goals and eligibility (modified Rankin Scale) | “Before this happened, could you walk independently? Care for yourself? Work? What activities could you do?” |
| Living situation | Affects disposition and rehabilitation planning | “Do you live alone or with family? Are there stairs in your home? Do you have help available?” |
| Occupation | May reveal exposures; impacts return-to-work planning | “What kind of work do you do? Any exposure to toxins or extreme physical demands?” |
| Advance directives | Critical for decisions about aggressive intervention | “Do you have a healthcare proxy? Any advance directives? What would your wishes be for aggressive treatment?” |
Collateral History is Essential
Patients with acute neurologic deficits often cannot provide reliable history—they may have aphasia, confusion, or impaired awareness of their deficits (anosognosia). Always seek collateral information from family members, witnesses, emergency medical services personnel, or bystanders. Ask specifically: “What did you observe? When exactly did you last see them normal? Did they complain of anything before this happened?”
4. Physical Examination
A systematic approach to the neurologic examination for focal deficits
Examination Framework: The neurologic examination should be both systematic and focused. In the hyperacute setting, use the National Institutes of Health Stroke Scale (NIHSS) for rapid standardized assessment. For comprehensive evaluation, proceed systematically through mental status, cranial nerves, motor, sensory, coordination, and gait. Always correlate findings to localize the lesion anatomically.
General Inspection
- Level of consciousness: Alert, drowsy, stuporous, comatose? Use Glasgow Coma Scale if depressed
- Respiratory pattern: Cheyne-Stokes (bilateral hemispheric or diencephalic), central neurogenic hyperventilation (midbrain), ataxic breathing (medulla)
- Body position: Asymmetric posturing, facial droop, flaccid limb, abnormal head or eye position
- Spontaneous movements: Asymmetry of movement, seizure activity, tremor, myoclonus
- Signs of trauma: Bruising, lacerations, Battle sign (mastoid ecchymosis), raccoon eyes (periorbital ecchymosis)
Vital Signs
| Vital Sign | What to Look For | Clinical Significance |
|---|---|---|
| Blood pressure | Severely elevated (greater than 180/120), hypotensive, asymmetric between arms | Hypertensive emergency suggests hemorrhage; permissive hypertension in ischemic stroke; arm asymmetry suggests aortic dissection or subclavian stenosis |
| Heart rate and rhythm | Irregular rhythm (atrial fibrillation), bradycardia, tachycardia | Atrial fibrillation is major stroke risk; Cushing reflex (bradycardia with hypertension) suggests elevated intracranial pressure |
| Respiratory rate | Abnormal patterns, tachypnea, apnea | Abnormal patterns localize brainstem lesions; airway protection may be compromised |
| Temperature | Fever, hypothermia | Fever suggests infection (meningitis, encephalitis, abscess) or hypothalamic dysfunction; hyperthermia worsens ischemic injury |
| Oxygen saturation | Hypoxemia | Hypoxia worsens neurologic injury; may indicate aspiration |
| Glucose | Hypoglycemia (less than 60 mg/dL), severe hyperglycemia | Hypoglycemia mimics stroke and must be excluded immediately; hyperglycemia worsens ischemic outcomes |
Mental Status Examination
Level of Consciousness
Alert: Awake, aware, responds appropriately
Drowsy/Lethargic: Falls asleep but arousable with verbal stimuli
Stuporous: Arousable only with vigorous stimuli
Comatose: Unarousable; assess brainstem reflexes
Language and Speech
Aphasia testing: Spontaneous speech fluency, comprehension, repetition, naming
Broca’s aphasia: Non-fluent, intact comprehension, impaired repetition — frontal lesion
Wernicke’s aphasia: Fluent but nonsensical, impaired comprehension — temporal lesion
Dysarthria: Articulation problem, language intact — distinguish from aphasia
Attention and Neglect
- Orientation: Person, place, time, situation
- Attention: Digit span, months backward, serial sevens
- Hemispatial neglect: Visual extinction on double simultaneous stimulation, line bisection test, drawing a clock — suggests non-dominant parietal lesion
Cranial Nerve Examination
| Cranial Nerve | Test | Abnormality and Localization |
|---|---|---|
| II – Optic | Visual acuity, visual fields by confrontation, fundoscopy | Field cuts localize along visual pathway; papilledema indicates elevated intracranial pressure |
| III, IV, VI – Oculomotor, Trochlear, Abducens | Pupil size and reactivity, extraocular movements, ptosis | Dilated fixed pupil (CN III compression from herniation); gaze deviation toward lesion (frontal) or away (pontine); internuclear ophthalmoplegia (brainstem/multiple sclerosis) |
| V – Trigeminal | Facial sensation (all three divisions), corneal reflex, jaw strength | Sensory loss pattern helps localize; absent corneal reflex is early brainstem sign |
| VII – Facial | Facial symmetry at rest and with movement (raise eyebrows, close eyes tight, smile) | Upper motor neuron (forehead spared) versus lower motor neuron (entire face); central facial weakness common in stroke |
| VIII – Vestibulocochlear | Hearing (finger rub), nystagmus pattern | Central versus peripheral vertigo; direction-changing nystagmus suggests central cause |
| IX, X – Glossopharyngeal, Vagus | Palate elevation (“say ah”), gag reflex, voice quality | Uvula deviates away from lesion; dysphonia, dysphagia indicate bulbar dysfunction |
| XI – Accessory | Shoulder shrug, head turn against resistance | Weakness indicates lesion of nerve or nucleus in medulla |
| XII – Hypoglossal | Tongue protrusion, inspect for atrophy and fasciculations | Tongue deviates toward side of lesion; atrophy and fasciculations indicate lower motor neuron lesion |
Motor Examination
Inspection
- Atrophy: Suggests chronic denervation (lower motor neuron) or disuse
- Fasciculations: Visible muscle twitching suggests anterior horn cell disease
- Posturing: Decorticate (flexor, above red nucleus) versus decerebrate (extensor, below red nucleus)
Tone
- Spasticity: Velocity-dependent increase in tone (upper motor neuron); clasp-knife quality
- Rigidity: Velocity-independent, lead-pipe or cogwheel (basal ganglia)
- Flaccidity: Decreased tone (lower motor neuron or acute upper motor neuron)
Strength Testing (Medical Research Council Scale)
| Grade | Description |
|---|---|
| 5 | Normal strength against full resistance |
| 4 | Movement against gravity and some resistance |
| 3 | Movement against gravity only |
| 2 | Movement with gravity eliminated |
| 1 | Trace contraction, no movement |
| 0 | No contraction |
Key Muscle Groups to Test
Upper Extremity
- Shoulder abduction (C5, deltoid)
- Elbow flexion (C5-6, biceps)
- Elbow extension (C7, triceps)
- Wrist extension (C6-7, wrist extensors)
- Finger extension (C7, finger extensors)
- Finger abduction (T1, interossei)
- Grip strength
Lower Extremity
- Hip flexion (L1-2, iliopsoas)
- Hip extension (L5-S1, gluteus maximus)
- Knee extension (L3-4, quadriceps)
- Knee flexion (L5-S1, hamstrings)
- Ankle dorsiflexion (L4-5, tibialis anterior)
- Ankle plantarflexion (S1-2, gastrocnemius)
- Great toe extension (L5, extensor hallucis longus)
Pronator Drift Test
Sensitive Test for Subtle Weakness
Have the patient hold both arms extended in front with palms up and eyes closed for 10-20 seconds. In upper motor neuron weakness, the affected arm will pronate and drift downward. This test can detect mild weakness not apparent on direct strength testing. The leg equivalent is having the patient hold their legs up while supine—the weak leg will drift down.
Reflex Examination
| Reflex | Nerve Root | Hyperreflexia Suggests | Hyporeflexia Suggests |
|---|---|---|---|
| Biceps | C5-6 | Upper motor neuron lesion above this level | C5-6 radiculopathy or peripheral neuropathy |
| Triceps | C7 | Upper motor neuron lesion above this level | C7 radiculopathy or peripheral neuropathy |
| Brachioradialis | C5-6 | Upper motor neuron lesion above this level | C5-6 radiculopathy or peripheral neuropathy |
| Patellar (knee) | L3-4 | Upper motor neuron lesion above this level | L3-4 radiculopathy or peripheral neuropathy |
| Achilles (ankle) | S1 | Upper motor neuron lesion above this level | S1 radiculopathy or peripheral neuropathy |
Pathological Reflexes
- Babinski sign (extensor plantar response): Upgoing great toe with fanning of other toes indicates upper motor neuron lesion
- Hoffman sign: Flexion of thumb and index finger when flicking the middle fingernail; upper motor neuron lesion
- Clonus: Rhythmic oscillations (especially at ankle) with sustained stretch; indicates upper motor neuron lesion
Sensory Examination
Primary Modalities
Light touch: Tests dorsal columns and spinothalamic tracts
Pinprick (pain): Spinothalamic tract (crosses at spinal level)
Temperature: Spinothalamic tract (crosses at spinal level)
Vibration: Dorsal columns (ipsilateral ascent)
Proprioception: Dorsal columns (ipsilateral ascent)
Patterns of Sensory Loss
Hemisensory: Thalamus or cortical lesion (contralateral)
Sensory level: Spinal cord lesion at that level
Dermatomal: Nerve root lesion
Peripheral nerve: Specific nerve territory
Stocking-glove: Peripheral polyneuropathy
Dissociated: Preserved some modalities, lost others (brainstem or spinal cord)
Coordination and Gait
Cerebellar Testing
- Finger-to-nose: Dysmetria (past-pointing) and intention tremor indicate cerebellar dysfunction
- Heel-to-shin: Incoordination suggests cerebellar or sensory ataxia
- Rapid alternating movements: Dysdiadochokinesia indicates cerebellar dysfunction
- Rebound: Inability to check movement suggests cerebellar lesion
Gait Assessment
| Gait Pattern | Description | Localization |
|---|---|---|
| Hemiplegic gait | Circumduction of leg, arm held flexed | Contralateral hemisphere (upper motor neuron) |
| Spastic gait | Stiff, scissoring legs | Bilateral upper motor neuron (spinal cord, bilateral strokes) |
| Ataxic gait | Wide-based, unsteady, irregular steps | Cerebellar or sensory ataxia |
| Steppage gait | High stepping to clear foot drop | Peroneal nerve palsy or L5 radiculopathy |
| Waddling gait | Hip drop with each step | Proximal muscle weakness (myopathy) |
| Magnetic gait | Feet seem stuck to floor, shuffling | Normal pressure hydrocephalus, frontal lobe disease |
Expected Findings by Etiology
| Condition | Mental Status | Cranial Nerves | Motor/Sensory | Other Key Findings |
|---|---|---|---|---|
| Middle cerebral artery stroke | Aphasia (dominant) or neglect (non-dominant) | Gaze deviation toward lesion; central facial weakness | Contralateral hemiparesis (face/arm > leg); hemisensory loss | Homonymous hemianopia |
| Lacunar stroke (pure motor) | Normal | May have facial weakness | Contralateral hemiparesis (face/arm/leg equal); no sensory loss | No cortical signs (aphasia, neglect, visual field cut) |
| Brainstem stroke | May be drowsy; often intact if small | Cranial nerve palsies (ipsilateral to lesion) | Crossed deficits: ipsilateral CN, contralateral body | Vertigo, diplopia, dysarthria, dysphagia common |
| Cerebellar stroke | Alert initially; may decline with edema | Nystagmus, gaze abnormalities | No weakness; ipsilateral ataxia | Severe imbalance; headache; risk of herniation |
| Intracerebral hemorrhage | Often decreased consciousness | Similar to ischemic stroke pattern | Often more severe and progressive deficits | Headache, vomiting more common than ischemic stroke |
| Spinal cord compression | Normal | Normal | Bilateral weakness below level; sensory level; upper motor neuron signs below lesion | Bladder/bowel dysfunction; back pain at level |
| Bell’s palsy | Normal | Complete unilateral facial weakness (forehead involved) | Normal | Hyperacusis, altered taste; diagnosis of exclusion |
The NIHSS: Rapid Standardized Assessment
The National Institutes of Health Stroke Scale (NIHSS) is an 11-item standardized examination that quantifies stroke severity in approximately 5-10 minutes. Scores range from 0 (no deficit) to 42 (maximum deficit). It assesses: level of consciousness, gaze, visual fields, facial palsy, motor function (arm and leg), ataxia, sensory, language, dysarthria, and neglect/extinction. The NIHSS score guides treatment decisions (thrombolysis eligibility, thrombectomy consideration) and predicts outcomes. All providers managing stroke patients should be certified in NIHSS administration.
5. Differential Diagnosis
Systematic approach organized by probability, tempo, and anatomical localization
Acute Focal Neurologic Deficit (Onset within minutes to hours)
| Probability | Condition | Key Features | Red Flags |
|---|---|---|---|
| COMMON (approximately 70%) | Ischemic stroke | Sudden onset, maximal at start, deficit matches vascular territory, vascular risk factors | Within thrombolysis window (less than 4.5 hours); large vessel occlusion on imaging |
| COMMON | Transient ischemic attack | Complete resolution (typically within 1 hour), same risk factors as stroke | High short-term stroke risk (10-15% at 90 days); requires urgent workup |
| LESS COMMON (approximately 20%) | Intracerebral hemorrhage | Headache, vomiting, progressive deficits, hypertension, anticoagulation use | Expanding hematoma; signs of elevated intracranial pressure; herniation |
| LESS COMMON | Seizure with Todd’s paralysis | Witnessed seizure activity, post-ictal confusion, gradual resolution over hours | New-onset seizure requires brain imaging to exclude structural lesion |
| LESS COMMON | Hypoglycemia | Diabetes, insulin or sulfonylurea use, confusion, diaphoresis, rapid resolution with glucose | Glucose less than 60 mg/dL; prolonged hypoglycemia causes permanent injury |
| LESS COMMON | Migraine with aura (hemiplegic migraine) | Gradual spread over 20-60 minutes, visual aura, headache follows, prior similar episodes | First episode requires stroke exclusion; prolonged aura concerning |
| UNCOMMON BUT SERIOUS (approximately 10%) | Subarachnoid hemorrhage | Thunderclap headache, worst headache of life, meningismus, may have focal signs | Sentinel bleed; rebleeding risk; requires urgent aneurysm evaluation |
| UNCOMMON BUT SERIOUS | Arterial dissection (carotid or vertebral) | Neck pain, headache, Horner syndrome, young patient, recent trauma or manipulation | Can cause stroke; requires anticoagulation or antiplatelet therapy |
| UNCOMMON BUT SERIOUS | Cerebral venous sinus thrombosis | Headache, seizures, focal deficits not matching arterial territory, hypercoagulable state, pregnancy | May cause venous infarction or hemorrhage; requires anticoagulation |
Subacute Focal Neurologic Deficit (Days to weeks)
Step-by-Step Approach to Subacute Deficits:
- Step 1: Exclude stroke or hemorrhage that presented late — imaging is essential
- Step 2: Consider mass lesions — tumor, abscess, subdural hematoma
- Step 3: Evaluate for inflammatory or infectious causes — multiple sclerosis, encephalitis, vasculitis
- Step 4: Assess for metabolic or toxic etiologies if imaging unrevealing
| Probability | Condition | Approximate Frequency | Key Distinguishing Features |
|---|---|---|---|
| COMMON | Brain tumor (primary or metastatic) | 15-20% of subacute presentations | Progressive course, seizures, morning headache, personality change; edema may cause fluctuation |
| COMMON | Subdural hematoma | 10-15% | Elderly, anticoagulation, often forgotten minor trauma, fluctuating symptoms, bilateral possible |
| COMMON | Multiple sclerosis (acute relapse) | 10-15% (in young adults) | Young adult, prior episodes, optic neuritis, symptoms disseminated in space and time |
| LESS COMMON | Brain abscess | 5-10% | Fever, subacute headache, focal signs; predisposing factors (endocarditis, sinusitis, immunocompromise) |
| LESS COMMON | Encephalitis (viral or autoimmune) | 5-10% | Fever, altered mental status, seizures, behavioral change; herpes simplex encephalitis affects temporal lobes |
| LESS COMMON | Central nervous system vasculitis | Less than 5% | Headache, encephalopathy, multifocal deficits, may have systemic vasculitis features |
| UNCOMMON | Progressive multifocal leukoencephalopathy | Rare (immunocompromised) | Immunocompromised (HIV, transplant, natalizumab); progressive multifocal white matter lesions |
| UNCOMMON | Creutzfeldt-Jakob disease | Rare | Rapidly progressive dementia, myoclonus, ataxia; MRI shows cortical ribboning and basal ganglia changes |
Chronic Progressive Focal Deficit (Weeks to months)
| Condition | Typical Presentation | Key Diagnostic Clues |
|---|---|---|
| Slow-growing brain tumor (meningioma, low-grade glioma) | Insidious progression, seizures, subtle personality change | Imaging shows well-circumscribed mass; may be incidental finding |
| Chronic subdural hematoma | Elderly, gradual decline, fluctuating symptoms | Crescent-shaped collection on CT; may be bilateral; often no recalled trauma |
| Normal pressure hydrocephalus | Triad: gait apraxia, urinary incontinence, dementia (in that order) | Ventriculomegaly out of proportion to atrophy; improvement with large-volume lumbar puncture |
| Neurodegenerative disease with focal onset | Asymmetric parkinsonism (corticobasal syndrome), progressive aphasia | Insidious onset, steady progression, characteristic patterns on examination |
| Cervical spondylotic myelopathy | Gradual hand clumsiness, gait difficulty, neck pain | Upper motor neuron signs in legs, lower motor neuron in arms; MRI shows cord compression |
| Motor neuron disease (amyotrophic lateral sclerosis) | Progressive weakness, fasciculations, no sensory loss | Mixed upper and lower motor neuron signs; bulbar involvement; electromyography confirms |
Anatomical Approach to Localization
Cortical Lesions
Ischemic stroke (middle cerebral artery, anterior cerebral artery, posterior cerebral artery)
Hemorrhagic stroke
Brain tumor (glioma, metastasis, meningioma)
Brain abscess
Encephalitis (herpes simplex encephalitis)
Cortical venous thrombosis
Subcortical and Deep Lesions
Lacunar stroke (internal capsule, basal ganglia, pons)
Hypertensive hemorrhage (putamen, thalamus)
Multiple sclerosis plaques
Deep brain tumor
Toxoplasmosis (in immunocompromised)
Central pontine myelinolysis
Brainstem Lesions
Basilar artery stroke
Vertebral artery dissection
Pontine hemorrhage
Multiple sclerosis
Brainstem glioma
Listeria rhombencephalitis
Spinal Cord Lesions
Spinal cord compression (tumor, epidural abscess, hematoma)
Transverse myelitis
Spinal cord infarction
Multiple sclerosis
Cervical spondylotic myelopathy
Vitamin B12 deficiency (subacute combined degeneration)
Stroke Mimics: Conditions That Present Like Stroke
Approximately 20-30% of suspected strokes are mimics
These conditions can present with sudden focal deficits and may lead to inappropriate thrombolysis if not recognized:
| Stroke Mimic | Key Distinguishing Features | How to Differentiate |
|---|---|---|
| Hypoglycemia | Diabetes, insulin use, confusion, diaphoresis, tremor | Fingerstick glucose; resolves rapidly with glucose administration |
| Seizure with Todd’s paralysis | Witnessed convulsions, post-ictal confusion, gradual resolution | History from witnesses; improves over hours; EEG if uncertain |
| Migraine with aura | Gradual onset (20-60 min), positive symptoms (visual), headache follows | History of similar episodes; symptoms “march” gradually; complete resolution |
| Functional neurological disorder | Inconsistent examination, positive signs (Hoover sign), psychiatric history | Examination inconsistencies; give-way weakness; normal imaging |
| Peripheral vestibular disorder | Vertigo predominant, normal HINTS examination | HINTS battery (Head Impulse, Nystagmus, Test of Skew); peripheral pattern reassuring |
| Bell’s palsy | Isolated facial weakness including forehead, no other deficits | Lower motor neuron pattern (forehead weak); no limb weakness or sensory loss |
| Subdural hematoma | Subacute course, fluctuating symptoms, elderly | CT shows extra-axial collection; often bilateral |
| Brain tumor | Progressive course, seizures, papilledema | MRI shows mass with edema; enhancement pattern helps characterize |
Drug-Induced Focal Neurologic Deficits
| Drug or Drug Class | Mechanism | Characteristics | Management |
|---|---|---|---|
| Anticoagulants (warfarin, direct oral anticoagulants, heparin) | Increased bleeding risk leads to intracranial hemorrhage | Spontaneous or trauma-related hemorrhage; subdural or intracerebral | Reversal agents; neurosurgical evaluation |
| Cocaine and amphetamines | Vasospasm, hypertensive crisis, vasculitis | Ischemic or hemorrhagic stroke in young patients; hypertension at presentation | Blood pressure control; supportive care; avoid beta-blockers alone |
| Insulin and sulfonylureas | Hypoglycemia causes neuronal dysfunction | Focal deficits indistinguishable from stroke; resolves with glucose | Immediate glucose administration |
| Chemotherapy (methotrexate, cytarabine, 5-fluorouracil) | Direct neurotoxicity, leukoencephalopathy | Subacute onset during or after treatment; cerebellar or diffuse | Drug cessation; supportive care |
| Immunosuppressants (cyclosporine, tacrolimus) | Posterior reversible encephalopathy syndrome | Visual disturbance, seizures, headache; posterior predominant on MRI | Blood pressure control; reduce or stop offending agent |
| Lithium | Neurotoxicity at high levels | Tremor, ataxia, confusion; may have focal features | Check level; supportive care; hemodialysis if severe |
| Phenytoin | Cerebellar toxicity | Ataxia, nystagmus, dysarthria | Check level; dose adjustment |
Quick Reference: “If You See This, Think This”
| Clinical Clue | Think This First | Next Step |
|---|---|---|
| Sudden onset, maximal at start, vascular territory | Ischemic stroke | Activate stroke code; CT head; determine last known well time |
| Thunderclap headache with neck stiffness | Subarachnoid hemorrhage | CT head; if negative, lumbar puncture |
| Crossed deficits (ipsilateral face, contralateral body) | Brainstem stroke | MRI with diffusion-weighted imaging; vascular imaging |
| Young patient with neck pain and Horner syndrome | Carotid or vertebral dissection | CT angiography or MR angiography of head and neck |
| Bilateral leg weakness with sensory level | Spinal cord compression | Emergent MRI spine; neurosurgical consultation |
| Fluctuating symptoms in elderly on anticoagulation | Subdural hematoma | CT head without contrast |
| Progressive deficit with morning headache and seizures | Brain tumor | MRI brain with and without contrast |
| Young adult with prior episodes affecting different areas | Multiple sclerosis | MRI brain and spine with contrast; lumbar puncture |
| Fever with focal deficit and altered mental status | Encephalitis or brain abscess | MRI brain; lumbar puncture (if safe); empiric acyclovir |
| Deficit resolves with glucose administration | Hypoglycemia | Identify cause; adjust diabetic regimen |
| Witnessed seizure followed by focal weakness | Todd’s paralysis | Observe for resolution; brain imaging to exclude structural cause |
| Gradual visual aura spreading over 20 minutes, then headache | Migraine with aura | First episode requires imaging; subsequent episodes may not |
6. Diagnostic Investigations
A stepwise approach guided by clinical urgency and suspected etiology
Guiding Principle: In acute focal neurologic deficit, the primary goal is to differentiate ischemic stroke (potentially treatable with thrombolysis or thrombectomy) from hemorrhage and stroke mimics. Speed is critical—brain imaging should be obtained within minutes of arrival. Subsequent investigations depend on the clinical scenario and initial imaging findings.
Immediate Investigations (All Patients with Acute Deficit)
| Investigation | Purpose | What to Look For | Practical Points |
|---|---|---|---|
| Non-contrast CT head | Exclude hemorrhage; identify early ischemic changes | Hyperdensity (blood), hypodensity (infarct), mass effect, midline shift, hyperdense vessel sign | Must be done before thrombolysis; can be completed in less than 5 minutes; normal CT does not exclude ischemic stroke |
| Fingerstick glucose | Exclude hypoglycemia (stroke mimic) | Glucose less than 60 mg/dL mimics stroke; greater than 400 mg/dL may indicate diabetic emergency | Must be checked before or during thrombolysis decision; only laboratory test required before treatment |
| Electrocardiogram | Identify atrial fibrillation; detect concurrent myocardial infarction | Atrial fibrillation, acute ST changes, prior infarct pattern | Stroke and myocardial infarction may co-occur; atrial fibrillation found in 20-25% of strokes |
| Basic metabolic panel | Assess renal function, electrolytes | Renal dysfunction (affects contrast use), electrolyte abnormalities | Should not delay thrombolysis unless renal failure known |
| Complete blood count | Identify thrombocytopenia, severe anemia, polycythemia | Platelet count less than 100,000 is relative contraindication to thrombolysis | Should not delay treatment unless thrombocytopenia suspected |
| Coagulation studies (PT/INR, PTT) | Assess bleeding risk; detect anticoagulation | INR greater than 1.7 is contraindication to thrombolysis | Should not delay treatment unless anticoagulation suspected or known |
| Troponin | Detect concurrent myocardial infarction or injury | Elevated troponin suggests cardiac source or concurrent acute coronary syndrome | Stroke can cause troponin elevation; interpret in context |
Advanced Neuroimaging
CT-Based Protocols
| Modality | Indications | Key Findings | Limitations |
|---|---|---|---|
| CT angiography (head and neck) | All suspected large vessel strokes; thrombectomy evaluation | Large vessel occlusion, carotid stenosis, dissection, aneurysm | Requires contrast; radiation exposure |
| CT perfusion | Extended window thrombectomy evaluation (6-24 hours); wake-up strokes | Core infarct versus penumbra mismatch; guides intervention beyond traditional windows | Requires specialized software; may overestimate core in some cases |
MRI-Based Protocols
| Sequence | Purpose | Key Findings |
|---|---|---|
| Diffusion-weighted imaging (DWI) | Gold standard for acute ischemic stroke detection | Restricted diffusion (bright on DWI, dark on ADC) within minutes of stroke onset |
| FLAIR (Fluid-attenuated inversion recovery) | Detect subacute infarcts; estimate stroke timing | DWI-FLAIR mismatch suggests stroke within 4.5 hours (useful for wake-up strokes) |
| Gradient echo or SWI (susceptibility-weighted imaging) | Detect hemorrhage; microbleeds | Blooming artifact from blood products; multiple microbleeds suggest amyloid angiopathy |
| MR angiography | Non-invasive vascular imaging | Large vessel occlusion, stenosis, dissection |
| MRI with contrast | Tumor, abscess, inflammation evaluation | Enhancement patterns help characterize lesions |
CT versus MRI in Acute Stroke
CT is faster and more available, making it the standard for hyperacute stroke. However, MRI with diffusion-weighted imaging is more sensitive for acute ischemia (especially small infarcts and posterior fossa strokes) and can estimate stroke timing. Many centers use a rapid MRI protocol (“code stroke MRI”) that can be completed in 6-10 minutes. The choice depends on institutional capabilities and clinical scenario.
Vascular and Cardiac Investigations
For Suspected Ischemic Stroke or Transient Ischemic Attack
Vascular Imaging
- CT angiography (head and neck): First-line for large vessel evaluation; identifies occlusion, stenosis, dissection
- MR angiography: Alternative without radiation; may miss small dissections
- Carotid ultrasound: Screening for carotid stenosis; operator-dependent
- Transcranial Doppler: Detects intracranial stenosis; monitors for microemboli
- Conventional angiography: Gold standard but invasive; reserved for complex cases or intervention
Cardiac Evaluation
- Telemetry or Holter monitoring: Detect paroxysmal atrial fibrillation (30-day monitoring increases yield)
- Transthoracic echocardiography: Assess for thrombus, valvular disease, wall motion abnormalities
- Transesophageal echocardiography: Better for left atrial appendage thrombus, patent foramen ovale, aortic arch atheroma
- Bubble study: Detect right-to-left shunt (patent foramen ovale)
Targeted Investigations by Suspected Etiology
If Suspecting Intracerebral Hemorrhage
Initial Workup
- CT head: Confirms diagnosis; determines location and volume
- CT angiography: “Spot sign” predicts hematoma expansion; may show underlying vascular malformation
- Coagulation studies: INR, PTT, platelet count for reversal decisions
Further Evaluation
- MRI with SWI: Detect underlying tumor, cavernoma, microbleeds (suggests amyloid angiopathy or hypertensive disease)
- Conventional angiography: If vascular malformation suspected (young patient, lobar location)
- Repeat imaging: At 24 hours to assess for expansion
If Suspecting Subarachnoid Hemorrhage
Diagnostic Approach
- Non-contrast CT head: Sensitivity greater than 95% within 6 hours; decreases over time
- Lumbar puncture: If CT negative and clinical suspicion remains; look for xanthochromia
Aneurysm Evaluation
- CT angiography: First-line to identify aneurysm location
- Conventional angiography: Gold standard; allows treatment planning
- MR angiography: Alternative if CT angiography contraindicated
If Suspecting Multiple Sclerosis
Imaging
- MRI brain with and without contrast: Periventricular, juxtacortical, infratentorial lesions; enhancing (acute) versus non-enhancing (chronic)
- MRI spine: Spinal cord lesions; typically short segment
Cerebrospinal Fluid Analysis
- Oligoclonal bands: Present in more than 90% of multiple sclerosis; not in matched serum
- IgG index: Elevated indicates intrathecal immunoglobulin synthesis
- Cell count and protein: Mild pleocytosis and elevated protein may be present
If Suspecting Encephalitis or Central Nervous System Infection
| Investigation | Purpose | Key Findings |
|---|---|---|
| Lumbar puncture | Essential for diagnosis; obtain before antibiotics if possible (but do not delay antibiotics) | Pleocytosis (lymphocytic in viral, neutrophilic in bacterial), protein, glucose, opening pressure |
| Cerebrospinal fluid herpes simplex virus PCR | Diagnose herpes simplex encephalitis | Positive PCR is diagnostic; may be negative in first 24-72 hours |
| Cerebrospinal fluid culture and Gram stain | Identify bacterial pathogens | Positive in bacterial meningitis; abscess may have sterile cerebrospinal fluid |
| MRI brain with contrast | Characterize lesions; identify abscess or encephalitis pattern | Temporal lobe involvement in herpes simplex encephalitis; ring enhancement in abscess |
| Autoimmune encephalitis panel | Diagnose autoimmune causes (anti-NMDA receptor, LGI1, and others) | Specific antibodies; may require both serum and cerebrospinal fluid testing |
If Suspecting Spinal Cord Pathology
Urgent Imaging
- MRI entire spine with and without contrast: Gold standard; identifies compression, myelitis, tumor, abscess
- CT myelography: If MRI contraindicated or unavailable
Additional Studies
- Lumbar puncture: If myelitis suspected; after ruling out complete block
- Vitamin B12 and copper levels: If subacute combined degeneration suspected
- Aquaporin-4 (NMO-IgG) antibody: If neuromyelitis optica suspected
Evaluation for Young Patient with Stroke (Age less than 50)
Extended Workup for Cryptogenic Stroke in Young Patients
When standard stroke workup is unrevealing in a young patient, consider:
- Hypercoagulable panel: Protein C, protein S, antithrombin III, factor V Leiden, prothrombin gene mutation (test remote from acute event and off anticoagulation)
- Antiphospholipid antibodies: Lupus anticoagulant, anticardiolipin, anti-beta-2 glycoprotein I (repeat at 12 weeks if positive)
- Homocysteine level: Elevated levels increase stroke risk
- Sickle cell screening: In appropriate populations
- Transesophageal echocardiography with bubble study: Evaluate for patent foramen ovale and atrial septal aneurysm
- Extended cardiac monitoring: 30-day or implantable loop recorder to detect paroxysmal atrial fibrillation
- Vasculitis workup: ESR, CRP, ANA, ANCA if clinical suspicion
- Drug screen: Cocaine, amphetamines
Investigation Priority by Clinical Scenario
| Clinical Scenario | Immediate Priority | Secondary Investigations |
|---|---|---|
| Acute stroke within thrombolysis window | CT head, glucose, ECG | CT angiography, labs (do not delay treatment) |
| Acute stroke beyond thrombolysis window | CT head, CT angiography (for thrombectomy evaluation) | CT or MRI perfusion, MRI, cardiac workup |
| Suspected subarachnoid hemorrhage | CT head, CT angiography | Lumbar puncture if CT negative; conventional angiography |
| Suspected spinal cord compression | Emergent MRI spine | CT myelography if MRI unavailable |
| Subacute progressive deficit | MRI brain with contrast | Lumbar puncture, specialized studies based on findings |
| Transient ischemic attack (resolved deficit) | MRI with DWI, CT angiography, ECG | Echocardiography, extended cardiac monitoring, risk stratification |
7. Pattern Recognition and Clinical Decision-Making
Practical algorithms and decision pathways for focal neurologic deficits
Step 1: Is This an Emergency?
| Clinical Scenario | Urgency Level | Immediate Action |
|---|---|---|
| Acute focal deficit within 24 hours of onset | EMERGENT | Activate stroke code; CT head immediately; determine last known well time; assess for thrombolysis and thrombectomy eligibility |
| Thunderclap headache with or without focal signs | EMERGENT | CT head immediately; if negative, lumbar puncture; CT angiography if subarachnoid hemorrhage confirmed |
| Bilateral leg weakness with sensory level or bladder dysfunction | EMERGENT | Emergent MRI spine; neurosurgical consultation; steroids if cord compression confirmed |
| Decreasing level of consciousness with focal signs | EMERGENT | CT head; assess for herniation; neurosurgical consultation; consider intubation for airway protection |
| Transient deficit now resolved (suspected transient ischemic attack) | URGENT | Same-day evaluation; MRI with diffusion-weighted imaging, vascular imaging, ECG, telemetry; ABCD2 score for risk stratification |
| Subacute progressive deficit over days to weeks | URGENT | MRI brain with contrast within 24-48 hours; targeted workup based on findings |
| Chronic slowly progressive deficit | ROUTINE | Outpatient MRI; comprehensive neurologic evaluation; appropriate specialist referral |
Step 2: The Acute Stroke Algorithm
Time Goals for Acute Stroke (“Time Is Brain”):
- Door to physician: Less than 10 minutes
- Door to CT completion: Less than 25 minutes
- Door to CT interpretation: Less than 45 minutes
- Door to needle (thrombolysis): Less than 60 minutes (ideally less than 45 minutes)
- Door to groin puncture (thrombectomy): Less than 90 minutes
| Decision Point | If Yes | If No |
|---|---|---|
| Is glucose less than 60 mg/dL? | Give glucose; reassess—deficit may resolve completely | Continue stroke evaluation |
| Does CT show hemorrhage? | No thrombolysis; reverse anticoagulation if applicable; blood pressure control; neurosurgery consultation | Consider thrombolysis if within window and no contraindications |
| Is patient within 4.5 hours of last known well? | Evaluate for intravenous thrombolysis (alteplase or tenecteplase) | Evaluate for extended window intervention |
| Are there contraindications to thrombolysis? | Proceed directly to thrombectomy evaluation if large vessel occlusion present | Administer thrombolysis; then evaluate for thrombectomy |
| Does CT angiography show large vessel occlusion? | Evaluate for mechanical thrombectomy (up to 24 hours in selected patients) | Medical management; stroke unit admission |
| Is patient 6-24 hours from last known well with large vessel occlusion? | CT or MRI perfusion to assess core versus penumbra mismatch; thrombectomy if favorable | Medical management; secondary prevention |
Intravenous Thrombolysis: Key Contraindications
Absolute Contraindications
- Active internal bleeding
- Recent intracranial or spinal surgery (within 3 months)
- History of intracranial hemorrhage
- Known intracranial neoplasm or arteriovenous malformation
- Suspected aortic dissection
- Current severe uncontrolled hypertension (greater than 185/110 despite treatment)
- Active bleeding diathesis
- Platelet count less than 100,000
- INR greater than 1.7 or therapeutic anticoagulation
Relative Contraindications (Weigh Risks and Benefits)
- Minor or rapidly improving symptoms
- Major surgery within 14 days
- Recent gastrointestinal or urinary hemorrhage (within 21 days)
- Recent myocardial infarction (within 3 months)
- Seizure at onset (if residual deficit is post-ictal)
- Glucose less than 50 or greater than 400 mg/dL
- Pregnancy
- Recent lumbar puncture
Step 3: Pattern-Based Decision Algorithms
Algorithm A: Acute Hemiparesis
| Clinical Pattern | Most Likely Diagnosis | Action |
|---|---|---|
| Face and arm greater than leg weakness with aphasia or neglect | Middle cerebral artery stroke | Stroke code; CT; CT angiography; thrombolysis or thrombectomy evaluation |
| Leg greater than arm weakness | Anterior cerebral artery stroke | Stroke code; consider bilateral anterior cerebral artery territory if both legs affected |
| Pure motor hemiparesis (face, arm, leg equal) without cortical signs | Lacunar stroke (internal capsule or pons) | MRI confirms; typically not thrombectomy candidate; excellent prognosis |
| Hemiparesis with diabetes and glucose less than 60 mg/dL | Hypoglycemia (stroke mimic) | Give glucose; deficit should resolve within minutes; investigate cause |
| Hemiparesis following witnessed seizure, now improving | Todd’s paralysis | Observe; should resolve over hours; brain imaging to exclude structural lesion |
Algorithm B: Acute Brainstem Signs
| Clinical Pattern | Most Likely Diagnosis | Action |
|---|---|---|
| Vertigo, nystagmus, ataxia with abnormal HINTS examination | Posterior circulation stroke (cerebellar or brainstem) | MRI with diffusion-weighted imaging (CT often misses posterior fossa); evaluate for basilar occlusion |
| Crossed deficits (ipsilateral cranial nerve, contralateral body) | Brainstem stroke | MRI; vascular imaging; monitor for progression |
| Quadriparesis with preserved consciousness | Locked-in syndrome (ventral pons) | Emergent imaging; basilar artery occlusion evaluation; consider thrombectomy |
| Ipsilateral facial sensory loss, Horner syndrome, ataxia with contralateral body pain and temperature loss | Lateral medullary (Wallenberg) syndrome | MRI; evaluate for vertebral artery dissection |
Algorithm C: Acute Visual Disturbance
| Clinical Pattern | Most Likely Diagnosis | Action |
|---|---|---|
| Monocular vision loss, painless, acute | Central retinal artery occlusion or ophthalmic artery occlusion | Ophthalmology emergency; consider intra-arterial thrombolysis; evaluate for carotid disease |
| Homonymous hemianopia | Posterior cerebral artery stroke or optic radiation lesion | MRI; stroke workup if acute |
| Binocular diplopia with vertigo | Brainstem stroke | MRI with diffusion-weighted imaging; posterior circulation evaluation |
| Monocular vision loss with eye pain | Optic neuritis (multiple sclerosis) | MRI orbits and brain with contrast; visual evoked potentials |
“What Do I Do If…” Decision Reference
| Clinical Situation | Immediate Action | Next Step |
|---|---|---|
| Patient arrives with acute deficit but last known well time is unknown | Treat as “wake-up stroke”; proceed with CT, CT angiography, MRI | DWI-FLAIR mismatch or perfusion imaging may identify candidates for intervention |
| Patient on warfarin with INR 3.5 and acute deficit | CT head immediately; if hemorrhage, give 4-factor prothrombin complex concentrate and vitamin K | If ischemic stroke and INR less than 1.7 after reversal, may consider thrombolysis; thrombectomy is option |
| Patient on direct oral anticoagulant (apixaban, rivaroxaban, dabigatran) | CT head; check when last dose taken | If hemorrhage, give specific reversal agent (idarucizumab for dabigatran; andexanet alfa for factor Xa inhibitors); thrombolysis generally contraindicated |
| Symptoms rapidly improving during evaluation | Continue full stroke workup; do not discharge based on improvement alone | MRI with diffusion-weighted imaging may show infarct; high recurrence risk; admit for evaluation |
| Patient develops worsening headache and declining consciousness after thrombolysis | Stop thrombolysis immediately; emergent CT head (suspect hemorrhagic conversion) | If hemorrhage confirmed, reverse fibrinolysis (cryoprecipitate, tranexamic acid); neurosurgery consultation |
| Young patient with stroke and no vascular risk factors | Standard acute stroke protocol | Extended workup: dissection (CT angiography neck), hypercoagulable panel, echocardiography with bubble study, vasculitis screen, drug screen |
| Acute paraparesis with sensory level | Emergent MRI entire spine; dexamethasone if cord compression suspected | Neurosurgical decompression within hours if compressive lesion; prognosis depends on speed of intervention |
| CT shows large territory infarct with midline shift | Neurosurgical consultation for decompressive craniectomy consideration | In selected patients less than 60 years with malignant middle cerebral artery infarction, craniectomy improves survival |
Transient Ischemic Attack: Rapid Risk Stratification
ABCD2 Score for Transient Ischemic Attack Risk
Predicts 2-day stroke risk after transient ischemic attack:
- Age 60 years or older: 1 point
- Blood pressure 140/90 mmHg or higher at presentation: 1 point
- Clinical features: Unilateral weakness: 2 points; Speech disturbance without weakness: 1 point
- Duration: 60 minutes or longer: 2 points; 10-59 minutes: 1 point
- Diabetes: 1 point
Interpretation: Score 0-3 = lower risk (1% 2-day stroke risk); Score 4-5 = moderate risk (4%); Score 6-7 = high risk (8%). However, all transient ischemic attack patients warrant urgent evaluation regardless of score—imaging findings (diffusion-weighted imaging positive, large vessel stenosis) may indicate higher risk than clinical score suggests.
Troubleshooting: Deficit Not Explained by Initial Workup
Systematic Re-Evaluation Questions
- Was the correct imaging obtained? (MRI with diffusion-weighted imaging is more sensitive than CT for acute ischemia, especially posterior fossa and small infarcts)
- Is the localization correct? (Review examination—could this be peripheral rather than central?)
- Were stroke mimics excluded? (Recheck glucose; consider seizure, migraine, functional disorder)
- Is this a rare stroke mechanism? (Dissection, vasculitis, hypercoagulable state, endocarditis)
- Could there be multiple lesions? (Multifocal process such as multiple sclerosis, vasculitis, metastases)
- Is additional history available? (Collateral information, prior episodes, psychiatric history)
- Should specialized consultation be obtained? (Neurology, neuro-ophthalmology, neurosurgery)
8. Clinical Pearls and Pitfalls
Practical wisdom — learn from successes and avoid common mistakes
Must-Know Clinical Pearls
Time is brain: In large vessel ischemic stroke, approximately 1.9 million neurons die every minute. Earlier treatment leads to better outcomes—every 15-minute reduction in door-to-needle time is clinically meaningful.
Last known well, not symptom onset: The critical time for treatment eligibility is when the patient was last known to be at their neurologic baseline, not when symptoms were first noticed. For wake-up strokes, this is when they went to sleep.
Always check glucose first: Hypoglycemia is the great stroke mimic and is immediately reversible. A fingerstick glucose should be obtained within minutes of arrival—before or during CT scanning.
CT negative does not mean no stroke: Non-contrast CT is highly sensitive for hemorrhage but may be completely normal in the first hours of ischemic stroke. A normal CT in a patient with clinical stroke should prompt thrombolysis consideration, not reassurance.
Posterior fossa strokes are often missed: CT is particularly insensitive for brainstem and cerebellar strokes. If clinical suspicion is high and CT is negative, obtain MRI with diffusion-weighted imaging. Cerebellar strokes can cause rapid deterioration from edema and herniation.
Transient ischemic attack is a neurologic emergency: Complete resolution of symptoms does not mean low risk. Transient ischemic attack patients have 10-15% 90-day stroke risk, with highest risk in the first 48 hours. Same-day workup and intervention dramatically reduces subsequent stroke.
The HINTS examination outperforms imaging for acute vertigo: In acute vestibular syndrome, a bedside HINTS examination (Head Impulse, Nystagmus pattern, Test of Skew) by a trained examiner is more sensitive than early MRI for detecting stroke. A “central” HINTS pattern mandates further evaluation even with negative imaging.
Young stroke requires extended workup: In patients under 50 without traditional vascular risk factors, pursue dissection, patent foramen ovale, hypercoagulable states, and vasculitis. Up to one-third of young strokes remain cryptogenic even after thorough evaluation.
Critical Pitfalls to Avoid
Waiting for laboratory results to give thrombolysis: The only laboratory test required before thrombolysis is glucose. Do not wait for coagulation studies, complete blood count, or chemistry unless the patient is known to be on anticoagulants or have a bleeding disorder.
Dismissing “improving” symptoms: Symptoms that are improving may still represent significant stroke. Fluctuating deficits are common and may herald complete occlusion. Never discharge a patient based on improvement alone without completing the workup.
Attributing vertigo to “inner ear” without proper examination: Posterior circulation stroke commonly presents with vertigo. The presence of other brainstem signs, central nystagmus patterns, or a positive HINTS examination should prompt urgent evaluation for stroke.
Missing spinal cord compression: Bilateral leg weakness with bladder dysfunction is a surgical emergency. Hours of delay can mean the difference between walking and permanent paraplegia. Obtain emergent MRI and neurosurgical consultation immediately.
Confusing aphasia with confusion: Patients with aphasia may appear confused because they cannot communicate effectively, but their cognition may be intact. Carefully distinguish language deficits from encephalopathy—they have very different localizations and etiologies.
Forgetting to ask about anticoagulation: Patients on anticoagulants have dramatically altered management. Always ask about blood thinners—including aspirin, warfarin, and direct oral anticoagulants. Check the medication list and verify with pharmacy records if possible.
Over-reliance on age to exclude stroke: While stroke is more common in elderly patients, it can occur at any age. Young patients with focal deficits deserve the same urgent evaluation as older patients. Dissection and cardiac sources are particularly common in young stroke.
Diagnosing Bell’s palsy without a complete examination: Isolated lower motor neuron facial weakness (Bell’s palsy) should be a diagnosis of exclusion. Ensure there are no other cranial nerve findings, limb weakness, or brainstem signs that would suggest stroke or other central pathology.
Key Takeaways
- Acute focal neurologic deficit is a medical emergency until proven otherwise—assume stroke and activate appropriate protocols immediately.
- Document the “last known well” time precisely; this determines treatment eligibility and is more important than when symptoms were noticed.
- Check fingerstick glucose immediately—hypoglycemia is a reversible stroke mimic that must be excluded before or during imaging.
- A normal CT does not exclude ischemic stroke; it excludes hemorrhage and identifies patients who may be candidates for thrombolysis.
- The pattern of deficits allows anatomical localization before imaging—use this to guide the differential diagnosis and interpret imaging findings.
- Upper motor neuron signs (spasticity, hyperreflexia, Babinski) indicate central nervous system lesions; lower motor neuron signs (flaccidity, atrophy, fasciculations) indicate peripheral lesions.
- Crossed findings (ipsilateral cranial nerve deficit with contralateral body deficit) localize to the brainstem.
- Posterior fossa strokes are commonly missed by CT; have a low threshold for MRI when clinical suspicion is present.
- Transient ischemic attack requires the same urgent workup as completed stroke—the risk of subsequent stroke is highest in the first 48 hours.
- Bilateral leg weakness with a sensory level and bladder dysfunction indicates spinal cord pathology and requires emergent MRI and neurosurgical evaluation.
- Approximately 20-30% of suspected strokes are mimics—hypoglycemia, seizures, migraine, and functional disorders must be considered.
- Young patients with stroke require extended workup for dissection, hypercoagulable states, patent foramen ovale, and vasculitis.
Quick Reference Algorithm
Systematic Approach to Acute Focal Neurologic Deficit:
- Recognize and activate: Any sudden focal deficit should trigger immediate evaluation; activate stroke code if within 24 hours of onset.
- Stabilize and assess: ABCs, vital signs, fingerstick glucose, brief neurologic examination (NIHSS if stroke suspected).
- Establish timing: Determine “last known well” time precisely; this drives all treatment decisions.
- Image immediately: Non-contrast CT to exclude hemorrhage; CT angiography if large vessel occlusion suspected.
- Treat aggressively: Thrombolysis within 4.5 hours if eligible; thrombectomy for large vessel occlusion up to 24 hours in selected patients.
- Diagnose the mechanism: Vascular imaging, cardiac evaluation, and laboratory studies to determine stroke etiology and guide secondary prevention.
- Prevent recurrence: Antiplatelet or anticoagulation therapy, statin, blood pressure management, and risk factor modification based on stroke mechanism.
- Rehabilitate: Early mobilization, physical and occupational therapy, speech therapy as indicated; stroke unit care improves outcomes.