Clinical Approach to Spasticity
Comprehensive Practical Framework1. Symptom Overview
Understanding the clinical significance and classification of spasticity and stiffness
Spasticity affects approximately 12 million people worldwide, with an estimated prevalence of 28-38% following stroke, 60-80% in patients with multiple sclerosis, and up to 65-78% of individuals with spinal cord injury. In the United States alone, over 500,000 people live with spasticity significant enough to require treatment. The economic burden is substantial, with annual healthcare costs for spasticity-related care exceeding $15 billion. Despite its prevalence, spasticity remains frequently underdiagnosed and undertreated, with studies suggesting that fewer than 50% of affected patients receive adequate management.
Definition
Spasticity is a motor disorder characterized by a velocity-dependent increase in tonic stretch reflexes (muscle tone) with exaggerated tendon jerks, resulting from hyperexcitability of the stretch reflex as one component of the upper motor neuron syndrome. It is classically described as a “catch” or increased resistance to passive movement that increases with the speed of stretch.
Stiffness is a broader term describing resistance to movement that may arise from neural (spasticity, rigidity, dystonia) or non-neural (contracture, fibrosis, joint pathology) mechanisms. Distinguishing between these causes is essential for appropriate management.
Key Epidemiological Statistics
- Stroke: 20-40% develop spasticity within 3 months; 17-43% at 12 months
- Multiple sclerosis: 60-80% experience spasticity during disease course
- Spinal cord injury: 65-78% develop spasticity within first year
- Traumatic brain injury: 13-20% have clinically significant spasticity
- Cerebral palsy: 70-80% of adults have spastic-type motor impairment
Classification by Temporal Profile
| Category | Timeframe | Common Causes | Clinical Significance |
|---|---|---|---|
| Acute Onset | Hours to days | Stroke, spinal cord injury, traumatic brain injury, transverse myelitis | Often preceded by flaccid phase; emergence suggests upper motor neuron recovery or evolving lesion |
| Subacute Development | Weeks to months | Post-stroke evolution, multiple sclerosis relapse, cord compression | Progressive increase requires reassessment; may indicate secondary complications or new pathology |
| Chronic/Established | Months to years | Established stroke, multiple sclerosis, hereditary spastic paraplegia, cerebral palsy | Focus shifts to functional impact, contracture prevention, and quality of life optimization |
Classification by Distribution
Focal Spasticity
Definition: Affecting one limb or specific muscle group
Examples: Post-stroke spastic hemiparesis affecting the hand, equinovarus foot deformity
Clinical implication: Often amenable to targeted treatments such as botulinum toxin injections
Regional Spasticity
Definition: Affecting multiple muscle groups in one region (hemibody or paraparesis pattern)
Examples: Spastic hemiplegia, spastic paraparesis from thoracic cord lesion
Clinical implication: May benefit from combination of focal and systemic therapies
Generalized Spasticity
Definition: Affecting all four limbs and often trunk muscles
Examples: Quadriplegia from cervical cord injury, advanced multiple sclerosis, hereditary spastic paraplegia
Clinical implication: Typically requires systemic oral medications or intrathecal therapy
Classification by Pattern and Etiology
| Pattern | Description | Suggests |
|---|---|---|
| Hemiplegic pattern | Unilateral upper and lower limb involvement with characteristic flexor posture in arm, extensor posture in leg | Cerebral lesion (stroke, tumor, traumatic brain injury) contralateral to affected side |
| Paraplegic pattern | Bilateral lower limb involvement with preserved upper limb function | Spinal cord lesion (thoracic myelopathy, hereditary spastic paraplegia, multiple sclerosis) |
| Quadriplegic pattern | All four limbs affected, often with truncal involvement | Cervical cord lesion, severe brain injury, advanced multiple sclerosis |
| Monoplegic pattern | Single limb involvement | Focal cortical lesion, incomplete cord injury, or structural limb abnormality |
| Fluctuating spasticity | Variable tone throughout the day or with activity | Multiple sclerosis, noxious stimuli (infection, pain), medication timing |
Distinguishing Spasticity from Other Forms of Increased Tone
| Type | Velocity Dependence | Quality | Associated Features | Pathology |
|---|---|---|---|---|
| Spasticity | Yes (increases with speed) | “Clasp-knife” phenomenon; catch and release | Hyperreflexia, Babinski sign, clonus, weakness | Upper motor neuron lesion |
| Rigidity | No (constant throughout range) | “Lead-pipe” or “cogwheel” (with tremor) | Bradykinesia, rest tremor, postural instability | Extrapyramidal (basal ganglia) |
| Dystonia | Variable | Sustained postures, twisting movements | Task-specific, sensory tricks may help | Basal ganglia, brainstem, or genetic |
| Paratonia (Gegenhalten) | Variable | Active resistance that varies with examiner effort | Frontal release signs, cognitive impairment | Frontal lobe dysfunction |
| Contracture | No | Fixed, non-neural resistance | Joint deformity, no velocity dependence | Soft tissue fibrosis, joint changes |
Key Concept: The Upper Motor Neuron Syndrome
Spasticity is just one component of the upper motor neuron syndrome. It is crucial to recognize that patients experience both positive phenomena (spasticity, hyperreflexia, clonus, spasms, abnormal reflexes) and negative phenomena (weakness, loss of dexterity, fatigue). Often, the negative features cause more functional disability than spasticity itself. Treatment must address both aspects and consider that reducing spasticity may unmask weakness.
Functional Impact of Spasticity
Potentially Beneficial Effects
- May support standing and transfers in weak limbs
- Can maintain muscle bulk and bone density
- May reduce risk of deep vein thrombosis through muscle activity
- Some patients use extensor spasms functionally for transfers
Harmful Effects
- Pain and discomfort
- Sleep disturbance from nocturnal spasms
- Interference with mobility, transfers, and positioning
- Difficulty with hygiene and nursing care
- Development of contractures and deformities
- Pressure injury risk from positioning difficulties
2. Pathophysiology and Mechanisms
Understanding the neural basis of spasticity and the upper motor neuron syndrome
Spasticity results from an imbalance between excitatory and inhibitory influences on alpha motor neurons in the spinal cord, caused by disruption of descending supraspinal pathways. Understanding these mechanisms is essential because different etiologies may preferentially affect different pathways, and emerging treatments target specific mechanisms within this complex circuitry.
The Stretch Reflex Arc
The monosynaptic stretch reflex forms the foundation of understanding spasticity. Under normal conditions, this reflex is modulated by multiple descending pathways. Loss of this modulation leads to hyperexcitable stretch reflexes.
| Component | Structure | Function | Role in Spasticity |
|---|---|---|---|
| Sensory Receptors | Muscle spindles (Ia afferents), Golgi tendon organs (Ib afferents) | Detect muscle length and rate of change; tendon tension | Increased spindle sensitivity contributes to hyperexcitability |
| Afferent Pathway | Ia and Ib sensory neurons via dorsal roots | Transmit proprioceptive information to spinal cord | Altered presynaptic inhibition increases reflex transmission |
| Spinal Integration | Alpha motor neurons, interneurons in ventral horn | Integrate sensory input with descending commands | Loss of inhibitory control leads to motor neuron hyperexcitability |
| Descending Modulation | Corticospinal, reticulospinal, vestibulospinal tracts | Provide excitatory and inhibitory control of spinal reflexes | Disruption of inhibitory pathways is primary mechanism |
| Efferent Pathway | Alpha motor neurons via ventral roots | Activate extrafusal muscle fibers | Increased firing leads to muscle hypertonicity |
| Effector | Skeletal muscle | Contract in response to motor neuron activation | Sustained contraction, co-contraction patterns, secondary changes |
Descending Motor Pathways and Their Role
Inhibitory Pathways (Loss Causes Spasticity)
Corticospinal tract (dorsal reticulospinal system):
- Primary pathway for voluntary movement
- Provides tonic inhibition to spinal reflexes
- Lesions lead to classic upper motor neuron signs
Dorsal reticulospinal tract:
- Originates from dorsal pontomedullary reticular formation
- Major source of inhibitory drive to spinal cord
- Damage produces significant spasticity
Facilitatory Pathways (Unopposed in Spasticity)
Medial reticulospinal tract:
- Originates from medial pontomedullary reticular formation
- Facilitates extensor tone in lower limbs
- Unopposed activity contributes to extensor spasticity
Vestibulospinal tract:
- Facilitates extensor muscle activity
- Contributes to postural tone and extensor posturing
- Explains lower limb extensor pattern after stroke
Mechanisms of Spasticity at Different Levels
| Level | Mechanism | Clinical Relevance |
|---|---|---|
| Supraspinal | Loss of descending inhibition from cortex and brainstem to spinal cord | Explains why cortical and subcortical lesions produce similar patterns; reticulospinal tract damage particularly important |
| Spinal – Presynaptic | Reduced presynaptic inhibition of Ia afferents allows greater reflex transmission | Target of baclofen (GABA-B agonist); explains velocity-dependence |
| Spinal – Postsynaptic | Reduced reciprocal inhibition; altered interneuron function; changes in motor neuron properties | Explains co-contraction patterns; motor neurons develop plateau potentials |
| Motor Neuron | Increased intrinsic excitability; development of persistent inward currents (plateau potentials) | Explains sustained muscle activity and spasms; target of emerging therapies |
| Muscle and Soft Tissue | Secondary changes: muscle fiber type changes, reduced sarcomeres, fibrosis, tendon shortening | Non-neural component of stiffness; may persist despite neural treatment; explains contracture |
Key Receptor Systems and Pharmacological Targets
GABA System
GABA-A receptors:
- Mediate fast postsynaptic inhibition
- Target of benzodiazepines
- Supraspinal and spinal effects
GABA-B receptors:
- Mediate presynaptic inhibition
- Target of baclofen
- Reduces neurotransmitter release
Glycine System
Glycine receptors:
- Major inhibitory system in spinal cord
- Reduced glycinergic inhibition in spasticity
Alpha-2 adrenergic receptors:
- Modulate noradrenergic descending pathways
- Target of tizanidine
- Reduce excitatory input
Calcium Channels
Voltage-gated calcium channels:
- Mediate muscle contraction coupling
- Target of dantrolene (acts at RyR1)
- Peripheral mechanism of action
Neuromuscular junction:
- Target of botulinum toxin
- Blocks acetylcholine release
- Focal, reversible paralysis
How Specific Conditions Cause Spasticity
| Condition | Mechanism | Typical Pattern | Time Course |
|---|---|---|---|
| Stroke (cerebral infarction or hemorrhage) | Damage to corticospinal and corticoreticular pathways; disruption of inhibitory drive to spinal cord | Contralateral hemiplegia; flexor pattern in arm (adducted shoulder, flexed elbow and wrist), extensor pattern in leg | Flaccid initially; spasticity emerges days to weeks later |
| Multiple sclerosis | Demyelination of descending pathways at multiple levels; loss of both excitatory and inhibitory control | Variable; often spastic paraparesis; may fluctuate with relapses and disease activity | Progressive accumulation; may vary with disease activity |
| Spinal cord injury | Complete or partial loss of descending inhibitory control; spinal cord reorganization below lesion level | Below level of lesion; paraplegia (thoracic) or quadriplegia (cervical); often severe with spasms | Emerges as spinal shock resolves (weeks to months) |
| Hereditary spastic paraplegia | Axonal degeneration of corticospinal tracts, typically longest axons first (dying-back pattern) | Slowly progressive spastic paraparesis; legs affected more than arms | Gradual onset and progression over years |
| Traumatic brain injury | Diffuse axonal injury and focal lesions affecting motor pathways; variable depending on injury pattern | Variable; may be hemiplegic, paraplegic, or generalized depending on injury location | Emerges during recovery phase |
| Cervical spondylotic myelopathy | Chronic compression of spinal cord with demyelination and axonal loss of descending pathways | Spastic quadriparesis; often with lower motor neuron signs at level of compression | Gradual progression; may have stepwise decline |
Secondary Soft Tissue Changes
Over time, chronic spasticity leads to structural changes in muscle and connective tissue that contribute to stiffness independently of neural mechanisms. These changes are critical to recognize because they do not respond to antispasticity medications.
| Change | Mechanism | Clinical Consequence | Treatment Implication |
|---|---|---|---|
| Muscle fiber shortening | Loss of sarcomeres due to sustained shortened position | Reduced range of motion; muscle contracture | Stretching, serial casting, surgical lengthening may be needed |
| Fibrosis | Increased collagen deposition in muscle and tendon | Increased passive stiffness not responsive to neural blockade | Medications ineffective; may require surgical release |
| Fiber type changes | Shift from Type I to Type II fibers; atrophy | Reduced endurance; increased fatigability | Rehabilitation and strengthening important |
| Joint contracture | Capsular fibrosis, cartilage changes from disuse | Fixed joint deformity | Prevention through positioning and range of motion exercises |
Often Overlooked Mechanism: The Role of Noxious Stimuli
Spasticity is highly modifiable by peripheral inputs. Noxious stimuli below the level of a spinal cord lesion can dramatically increase spasticity through spinal reflex mechanisms. Common culprits include urinary tract infections, constipation or fecal impaction, ingrown toenails, pressure injuries, tight clothing or orthoses, and occult fractures. Any sudden increase in spasticity should prompt a search for these treatable causes before escalating antispasticity medications. This phenomenon occurs because nociceptive afferents converge on spinal interneurons that modulate stretch reflexes.
Emerging Concept: Persistent Inward Currents and Plateau Potentials
Motor neurons in chronic spasticity develop persistent inward currents (PICs) mediated by voltage-gated calcium and sodium channels. These create plateau potentials that allow motor neurons to remain active with minimal synaptic input. This explains prolonged muscle spasms and the difficulty in voluntarily relaxing spastic muscles. Serotonin and norepinephrine modulate PICs, which may explain why selective serotonin reuptake inhibitors can sometimes worsen spasticity. Understanding this mechanism is driving development of novel treatments targeting specific ion channels.
3. History Taking
A comprehensive approach to eliciting the spasticity and stiffness history
Red Flags — Require Urgent Evaluation
- Acute onset with back pain — Spinal cord compression (tumor, abscess, hematoma)
- Bladder or bowel dysfunction — Cauda equina syndrome or myelopathy
- Rapidly progressive weakness — Compressive lesion, inflammatory myelitis
- Fever with new spasticity — Epidural abscess, meningitis, encephalitis
- Sudden worsening of established spasticity — Noxious stimulus (infection, fracture, pressure injury)
- Sensory level on trunk — Spinal cord lesion requiring imaging
- Associated severe headache — Intracranial pathology (stroke, mass lesion)
- Recent trauma with new symptoms — Spinal cord or brain injury
Systematic History: The “SPASTIC” Approach
Use the mnemonic “SPASTIC” to ensure comprehensive history taking for patients presenting with increased muscle tone:
- S — Site and Spread: Where did stiffness begin? How has it spread? Which limbs are affected?
- P — Pace and Progression: How quickly did it develop? Is it stable, improving, or worsening?
- A — Aggravating and Alleviating factors: What makes it worse (cold, stress, movement)? What helps (warmth, rest, positioning)?
- S — Spasms and Associated symptoms: Are there painful spasms? Associated weakness, sensory changes, bladder issues?
- T — Timing and Triggers: When is it worst (morning, evening, with activity)? Any identifiable triggers?
- I — Impact on function: How does it affect mobility, self-care, sleep, work, and quality of life?
- C — Cause and Context: Known neurological diagnosis? Prior stroke, injury, surgery? Family history of similar problems?
Key Questions About Onset and Progression
| Temporal Pattern | Key Questions to Ask | Diagnostic Implications |
|---|---|---|
| Acute onset (hours to days) | “When exactly did you first notice the stiffness?” “Was there any preceding event—trauma, illness, headache?” | Stroke, spinal cord injury, transverse myelitis, epidural abscess |
| Subacute (weeks to months) | “Has the stiffness been gradually increasing?” “Are there periods when it’s better or worse?” | Multiple sclerosis relapse, compressive myelopathy, post-stroke evolution |
| Chronic progressive | “Over what period of time has this developed?” “Can you identify when it first started?” | Hereditary spastic paraplegia, primary progressive multiple sclerosis, cervical spondylotic myelopathy |
| Fluctuating | “Does the stiffness vary throughout the day?” “Are there good days and bad days?” | Multiple sclerosis, medication wearing off, noxious stimuli, fatigue-related worsening |
Targeted Questions by Suspected Cause
| Suspected Cause | Key Features | Ask This Question |
|---|---|---|
| Stroke | Unilateral onset, vascular risk factors, sudden presentation | “Did your symptoms come on suddenly?” “Do you have high blood pressure, diabetes, or heart problems?” |
| Multiple sclerosis | Relapsing symptoms, sensory disturbances, young adult onset | “Have you ever had episodes of numbness, vision problems, or weakness that came and went?” “Have you noticed any electric shock sensations down your spine when bending your neck?” |
| Spinal cord injury | Clear history of trauma, sensory level, bladder dysfunction | “Have you had any injury to your back or neck?” “Do you have numbness below a certain level on your body?” |
| Cervical spondylotic myelopathy | Neck pain, hand clumsiness, gait difficulty, older age | “Do you have neck pain or stiffness?” “Have you noticed difficulty with buttons or handwriting?” “Do you feel unsteady when walking?” |
| Hereditary spastic paraplegia | Family history, slowly progressive leg stiffness, onset often in youth | “Does anyone else in your family have similar walking difficulties or stiffness?” “When did you first notice problems with your legs?” |
| Motor neuron disease (amyotrophic lateral sclerosis) | Combined upper and lower motor neuron signs, fasciculations, bulbar symptoms | “Have you noticed muscle twitching under your skin?” “Any changes in your speech or swallowing?” “Have your muscles become thinner?” |
| Parasagittal meningioma | Progressive leg weakness, seizures, headache | “Have you had any seizures or convulsions?” “Any persistent headaches, particularly in the morning?” |
| Stiff person syndrome | Episodic spasms, truncal rigidity, startle response, autoimmune associations | “Do sudden noises or surprises trigger severe muscle spasms?” “Is there a board-like stiffness in your trunk?” “Do you have diabetes or thyroid problems?” |
Critical Associated Symptoms to Elicit
Symptoms Suggesting Spinal Cord Pathology
- Sensory level: “Is there a line on your body below which sensation is different?”
- Band-like sensation: “Do you feel a tight band around your chest or abdomen?”
- Bladder dysfunction: “Any difficulty starting urination, urgency, or incontinence?”
- Bowel dysfunction: “Any constipation or loss of bowel control?”
- Sexual dysfunction: “Any changes in sexual function?”
- Lhermitte’s sign: “Do you get electric shock sensations down your spine when you bend your neck?”
Symptoms Suggesting Cerebral Pathology
- Cognitive changes: “Have you noticed any memory or thinking problems?”
- Speech difficulties: “Any trouble finding words or slurred speech?”
- Visual disturbance: “Any vision changes or double vision?”
- Seizures: “Have you had any episodes of shaking or loss of awareness?”
- Headache: “Any new or severe headaches?”
- Facial weakness: “Has your face drooped on one side?”
Characterizing Spasms
| Spasm Characteristic | Questions to Ask | Clinical Significance |
|---|---|---|
| Frequency | “How often do you get spasms? Several times a day? Hourly?” | Frequent spasms significantly impact quality of life and may indicate inadequate treatment or noxious stimulus |
| Triggers | “What sets off your spasms? Movement, touch, cold, full bladder?” | Identifiable triggers may be modifiable; full bladder and bowel are common reversible causes |
| Pattern | “Do your legs draw up (flexor) or push out straight (extensor)?” | Flexor spasms more common in incomplete lesions; extensor spasms may be used functionally for transfers |
| Pain | “Are the spasms painful? How severe on a scale of 0-10?” | Painful spasms significantly affect quality of life and are a treatment priority |
| Sleep disruption | “Do spasms wake you at night? How often?” | Nocturnal spasms are a major source of disability and may need specific nighttime treatment |
Assessing Functional Impact
Key Functional Domains to Assess
The decision to treat spasticity depends heavily on its functional impact. Ask specifically about:
- Mobility: “Can you walk? Use a wheelchair? Transfer independently?”
- Self-care: “Can you dress yourself, including lower body? Manage personal hygiene?”
- Positioning: “Can you sit comfortably? Do you have difficulty with seating or lying in bed?”
- Sleep: “Does stiffness or spasms affect your sleep?”
- Pain: “Is the stiffness itself painful, or do you have associated pain?”
- Caregiving: “Do caregivers have difficulty with your positioning, hygiene, or dressing?”
Important: Some patients use their spasticity functionally (e.g., extensor tone for standing transfers). Always ask: “Does the stiffness help you do anything, like stand or transfer?”
Medication and Treatment History
Medications That Can Worsen Spasticity
- Selective serotonin reuptake inhibitors (SSRIs) — May increase spasticity through serotonergic effects on motor neurons
- Lithium — Can exacerbate spasticity and cause tremor
- Stimulants — Amphetamines, methylphenidate may increase tone
- Withdrawal from baclofen — Abrupt cessation causes severe rebound spasticity, potentially life-threatening
- Withdrawal from benzodiazepines — Can precipitate increased tone and spasms
Current and Prior Antispasticity Treatment
- Oral medications: Which ones? What doses? Side effects? Efficacy?
- Botulinum toxin: Which muscles? When was last injection? Response?
- Intrathecal baclofen: Is there a pump? When was it implanted? Current dose?
- Physical therapy: Current program? Stretching regimen?
- Surgical procedures: Prior tendon releases, rhizotomy, or other procedures?
Screen for Noxious Stimuli (Especially in Spinal Cord Injury)
Any sudden worsening of spasticity should prompt investigation for treatable causes:
- Urinary tract infection: “Any burning, frequency, cloudy urine, or fever?”
- Constipation or fecal impaction: “When was your last bowel movement? Any abdominal discomfort?”
- Pressure injuries: “Any skin breakdown or sores?”
- Ingrown toenails: “Any foot pain or nail problems?”
- Tight clothing or equipment: “Are orthoses, shoes, or catheter straps too tight?”
- Occult fracture: “Any recent falls or injuries, even minor ones?”
- Deep vein thrombosis: “Any leg swelling, warmth, or redness?”
Social and Family History
Family History
- Hereditary spastic paraplegia: “Does anyone in your family have difficulty walking or leg stiffness?”
- Multiple sclerosis: “Any family members with MS?”
- Other neurological conditions: “Any family history of muscle or nerve problems?”
- Consanguinity: Important for recessive conditions
Social and Support Assessment
- Living situation: “Do you live alone or with family/caregivers?”
- Caregiver burden: “Who helps with your care? How are they coping?”
- Equipment: “Do you use a wheelchair, walker, orthoses?”
- Home accessibility: “Are there stairs? Is your bathroom accessible?”
- Employment: “Has this affected your ability to work?”
4. Physical Examination
A systematic neurological approach for evaluating spasticity and stiffness
Systematic Framework: Use the “General → Tone → Power → Reflexes → Sensory → Coordination → Gait” approach for complete neurological examination of patients presenting with spasticity. The examination should localize the lesion (cerebral versus spinal) and characterize the pattern and severity of motor impairment.
General Inspection
- Posture: Look for hemiplegic posture (flexed upper limb, extended lower limb), scissoring of legs, opisthotonic posturing
- Spontaneous movements: Note any dystonic postures, tremor, fasciculations, or involuntary spasms
- Muscle bulk: Assess for atrophy (suggests chronicity or lower motor neuron component) or preserved bulk
- Contractures: Observe for fixed deformities at joints (ankle equinus, hip or knee flexion contractures, wrist flexion)
- Skin: Check for pressure injuries, particularly over bony prominences
- Equipment: Note any orthoses, splints, wheelchair, walking aids
Vital Signs
| Vital Sign | What to Look For | Clinical Significance |
|---|---|---|
| Blood Pressure | Hypertension, labile blood pressure, orthostatic hypotension | Hypertension is a vascular risk factor for stroke; labile blood pressure may indicate autonomic dysreflexia in spinal cord injury |
| Heart Rate | Bradycardia or tachycardia, irregular rhythm | Atrial fibrillation is a stroke risk factor; bradycardia may accompany autonomic dysreflexia |
| Temperature | Fever | May indicate infection (urinary tract infection, pneumonia) as a trigger for worsening spasticity |
| Respiratory Rate | Tachypnea, shallow breathing, paradoxical breathing | May indicate respiratory muscle involvement in high cervical lesions or motor neuron disease |
Tone Assessment
Tone assessment is the cornerstone of spasticity evaluation. The patient must be relaxed, and you should examine tone in multiple muscle groups at varying velocities.
Technique for Assessing Tone
- Patient positioning: Supine with head in midline (head position affects tone); ensure patient is relaxed
- Support the limb: Hold the limb proximally and distally, supporting its weight
- Passive movement: Move the joint through its full range at slow, medium, and fast speeds
- Velocity dependence: Spasticity increases with faster movements—this distinguishes it from rigidity
- Feel for “catch”: A sudden increase in resistance followed by release (clasp-knife phenomenon)
Modified Ashworth Scale
| Grade | Description |
|---|---|
| 0 | No increase in muscle tone |
| 1 | Slight increase in tone with catch and release or minimal resistance at end of range of motion |
| 1+ | Slight increase in tone with catch followed by minimal resistance throughout less than half of the range of motion |
| 2 | More marked increase in tone through most of the range of motion, but limb easily moved |
| 3 | Considerable increase in tone; passive movement difficult |
| 4 | Limb rigid in flexion or extension |
Key Muscle Groups to Assess
Upper Limb
- Shoulder adductors: Abduct arm from adducted position
- Elbow flexors: Extend elbow from flexed position
- Elbow extensors: Flex elbow from extended position
- Wrist flexors: Extend wrist
- Finger flexors: Extend fingers
- Pronators: Supinate forearm
Lower Limb
- Hip adductors: Abduct hip (scissoring assessment)
- Hip flexors: Extend hip
- Knee extensors: Flex knee from extended position
- Knee flexors: Extend knee from flexed position
- Ankle plantarflexors: Dorsiflex ankle (equinus assessment)
- Ankle invertors: Evert foot
Distinguishing Spasticity from Other Tone Abnormalities
| Feature | Spasticity | Rigidity | Dystonia | Paratonia |
|---|---|---|---|---|
| Velocity dependence | Yes—increases with speed | No—constant | Variable | Variable |
| Quality | Clasp-knife (catch then give) | Lead-pipe or cogwheel | Sustained postures | Active resistance |
| Distribution | Antigravity muscles preferentially | Flexors and extensors equally | Task-specific or generalized | Generalized |
| Effect of relaxation | Decreases when fully relaxed | Persists | May decrease | May increase with attention |
| Reinforcement maneuver | No effect or mild increase | May unmask cogwheeling | Variable | N/A |
Reflex Examination
| Reflex | Spinal Level | Finding in Upper Motor Neuron Lesion |
|---|---|---|
| Biceps | C5-C6 | Hyperreflexia (3+ or 4+) with lesion above this level |
| Brachioradialis | C5-C6 | Hyperreflexia; inverted reflex (finger flexion instead) suggests C5-C6 lesion |
| Triceps | C7-C8 | Hyperreflexia with lesion above this level |
| Knee (patellar) | L3-L4 | Hyperreflexia with crossed adductor response possible |
| Ankle | S1-S2 | Hyperreflexia; clonus often present |
| Jaw jerk | Pons (CN V) | Brisk jaw jerk indicates lesion above foramen magnum |
Clonus Assessment
- Ankle clonus: Rapidly dorsiflex ankle and maintain pressure—sustained rhythmic oscillation indicates upper motor neuron lesion
- Patellar clonus: Rapidly push patella distally—rhythmic bouncing indicates hyperreflexia
- Grading: Unsustained (less than 5 beats) versus sustained (5 or more beats, or continuous)
Pathological Reflexes
| Reflex | Technique | Positive Response | Significance |
|---|---|---|---|
| Babinski sign | Stroke lateral plantar surface from heel to toes | Extension of great toe, fanning of other toes | Indicates corticospinal tract dysfunction |
| Hoffmann sign | Flick distal phalanx of middle finger | Flexion and adduction of thumb | Upper motor neuron sign in upper limbs |
| Crossed adductor reflex | Elicit knee jerk | Contralateral thigh adduction | Indicates hyperreflexia |
Power Assessment
Weakness is the “negative” component of the upper motor neuron syndrome and often causes more functional disability than spasticity itself.
| MRC Grade | Description |
|---|---|
| 0 | No contraction |
| 1 | Flicker or trace of contraction |
| 2 | Active movement with gravity eliminated |
| 3 | Active movement against gravity |
| 4 | Active movement against gravity and resistance |
| 5 | Normal power |
Pattern of Weakness in Upper Motor Neuron Lesions
Upper limb: Extensors weaker than flexors—difficulty with finger extension, wrist extension, elbow extension, shoulder abduction
Lower limb: Flexors weaker than extensors—difficulty with hip flexion, knee flexion, ankle dorsiflexion
This “pyramidal pattern” of weakness reflects the preferential involvement of antigravity muscles and explains the typical hemiplegic posture.
Sensory Examination
Sensory findings help localize the lesion level, particularly in spinal cord pathology.
Key Modalities to Test
- Pinprick (spinothalamic tract): Test bilaterally; look for a sensory level on trunk
- Light touch: Test bilaterally from distal to proximal
- Vibration (posterior columns): Use 128 Hz tuning fork on bony prominences
- Joint position sense (posterior columns): Test distal interphalangeal joints of fingers and great toes
- Romberg test: Tests proprioceptive function
Sensory Patterns
| Pattern | Description | Suggests |
|---|---|---|
| Sensory level | All modalities impaired below a dermatomal level | Complete or near-complete spinal cord lesion |
| Dissociated sensory loss | Spinothalamic loss (pain, temperature) with preserved posterior column function | Anterior cord syndrome, syringomyelia |
| Brown-Séquard pattern | Ipsilateral weakness and proprioceptive loss; contralateral pain and temperature loss | Hemisection of spinal cord |
| Cape distribution | Loss over shoulders and upper back bilaterally | Syringomyelia |
| Hemisensory loss | All modalities impaired on one side of body | Thalamic or cortical lesion |
Gait Assessment
Gait observation provides valuable information about the functional impact of spasticity and the pattern of motor involvement.
| Gait Pattern | Description | Associated Conditions |
|---|---|---|
| Spastic hemiplegic gait | Circumduction of affected leg; arm held flexed at elbow; reduced arm swing | Stroke, unilateral cerebral lesion |
| Spastic diplegic gait (scissoring) | Stiff legs crossing midline; “scissoring” pattern; toe walking | Bilateral corticospinal lesion, cerebral palsy |
| Spastic paraparetic gait | Stiff, slow leg movements; circumduction bilaterally; may need walking aids | Spinal cord lesion, hereditary spastic paraplegia |
| Equinovarus gait | Foot inverted and plantarflexed; walking on lateral border of foot | Ankle plantarflexor and invertor spasticity; post-stroke |
Expected Findings by Etiology
| Condition | Tone | Weakness Pattern | Reflexes | Sensory | Other Findings |
|---|---|---|---|---|---|
| Stroke | Unilateral; arm flexors, leg extensors | Pyramidal; contralateral hemiparesis | Unilateral hyperreflexia; Babinski | May have hemisensory loss | Facial weakness, aphasia, neglect possible |
| Multiple sclerosis | Variable; often asymmetric | Variable distribution | Hyperreflexia; may be asymmetric | Often abnormal; may be dissociated | Optic pallor, INO, cerebellar signs |
| Spinal cord injury | Below lesion level; bilateral | Paraplegia or quadriplegia | Hyperreflexia below lesion | Sensory level on trunk | Bladder dysfunction, autonomic signs |
| Cervical myelopathy | All four limbs; legs greater than arms | Quadriparesis; hand clumsiness | Hyperreflexia; inverted reflexes at level | May have sensory level | Lhermitte sign; gait ataxia |
| Hereditary spastic paraplegia | Legs greater than arms; symmetric | Legs much weaker than arms | Brisk in legs; Babinski bilateral | Often preserved or mild vibration loss | Pes cavus; progressive course |
| Motor neuron disease | Mixed UMN and LMN | Progressive; asymmetric initially | Mixed brisk and absent | Normal | Fasciculations, atrophy, bulbar signs |
Important Teaching Point
The examination may not reflect the full picture. Spasticity varies with patient positioning, anxiety, temperature, time of day, and bladder fullness. A single examination may underestimate or overestimate the typical severity. Ask patients and caregivers about usual tone levels and consider repeat assessments. Additionally, remember that contracture (non-neural stiffness) does not change with velocity and persists under anesthesia or nerve block—this distinction has important treatment implications.
Functional Assessment in Clinic
Observe These Functional Tasks
- Transfers: Bed to chair, chair to standing
- Walking: With and without aids; distance tolerance
- Reaching: Hand to mouth, overhead reach
- Grip: Ability to grasp and release objects
- Dressing: Especially lower body dressing
Standardized Assessment Tools
- Modified Ashworth Scale: Tone assessment (0-4)
- Tardieu Scale: Velocity-dependent catch
- Penn Spasm Frequency Scale: Spasm frequency
- 10-Meter Walk Test: Gait speed
- Action Research Arm Test: Upper limb function
5. Differential Diagnosis
Systematic approach organized by probability, anatomical location, and clinical features
The differential diagnosis of spasticity requires first establishing whether this is truly spasticity (velocity-dependent increase in tone from upper motor neuron dysfunction) versus other causes of increased tone or stiffness. Once spasticity is confirmed, the goal is to localize the lesion and identify the underlying etiology.
Acute Onset Spasticity (Hours to Days)
Acute onset of spasticity is unusual—most acute upper motor neuron lesions present initially with flaccidity. However, some conditions may present with early spasticity or rapid evolution from flaccid to spastic state.
| Probability | Condition | Key Features | Red Flags |
|---|---|---|---|
| COMMON | Stroke (cerebral infarction or hemorrhage) | Sudden onset hemiparesis; vascular risk factors; may evolve from flaccid to spastic over days to weeks | Sudden weakness, facial droop, speech changes, severe headache (hemorrhage) |
| COMMON | Worsening of established spasticity due to noxious stimulus | Patient with known spinal cord injury or other cause; sudden increase in baseline spasticity | Search for UTI, constipation, pressure injury, ingrown toenail, occult fracture |
| LESS COMMON | Spinal cord injury (traumatic) | History of trauma; spasticity emerges as spinal shock resolves (days to weeks after injury) | Sensory level, bladder dysfunction, history of trauma |
| LESS COMMON | Transverse myelitis | Bilateral leg weakness and sensory symptoms; may follow viral illness; progresses over hours to days | Rapid progression, sensory level, bladder retention |
| LESS COMMON | Multiple sclerosis relapse | New or worsening symptoms in patient with known or suspected MS; evolves over days | New neurological deficits, prior episodes, young adult |
| UNCOMMON BUT SERIOUS | Spinal epidural abscess | Back pain, fever, progressive weakness; risk factors include diabetes, immunosuppression, recent procedure | Fever, severe back pain, rapid progression—neurosurgical emergency |
| UNCOMMON BUT SERIOUS | Spinal cord compression (tumor, hematoma) | Progressive weakness with sensory level; back pain often present; may be acute if hemorrhage into tumor | Known malignancy, anticoagulation, rapid progression |
| UNCOMMON BUT SERIOUS | Baclofen withdrawal syndrome | Patient on intrathecal or high-dose oral baclofen; severe spasticity, hyperthermia, altered mental status | Life-threatening; check pump function, recent dose changes |
Chronic or Progressive Spasticity (Weeks to Years)
Step-by-Step Approach to Chronic Spasticity:
- Step 1: Confirm this is spasticity (velocity-dependent) rather than rigidity, dystonia, or contracture
- Step 2: Determine the pattern—hemiplegic (cerebral), paraplegic (spinal), or generalized
- Step 3: Review for known cause (prior stroke, trauma, established diagnosis)
- Step 4: If no known cause, investigate based on pattern and associated features
| Probability | Condition | Approximate Frequency | Key Distinguishing Features |
|---|---|---|---|
| COMMON | Post-stroke spasticity | Most common cause overall | Hemiplegic pattern; history of stroke; onset weeks after event; flexor arm, extensor leg posture |
| COMMON | Multiple sclerosis | 60-80% of MS patients | Relapsing-remitting or progressive course; often asymmetric; associated optic neuritis, sensory symptoms, fatigue |
| COMMON | Spinal cord injury (chronic) | 65-78% of SCI patients | History of trauma; level-dependent pattern; bladder and bowel dysfunction; sensory level |
| COMMON | Cerebral palsy (adult) | 70-80% spastic type | Lifelong history; non-progressive (though complications evolve); diplegic, hemiplegic, or quadriplegic patterns |
| LESS COMMON | Cervical spondylotic myelopathy | Most common cause of myelopathy over age 55 | Insidious onset; neck pain; hand clumsiness; gait difficulty; legs worse than arms; bladder symptoms late |
| LESS COMMON | Traumatic brain injury | 13-20% have significant spasticity | History of head injury; variable pattern depending on lesion location; may have cognitive impairment |
| LESS COMMON | Hereditary spastic paraplegia | Prevalence 2-10 per 100,000 | Family history (may be absent in recessive forms); slowly progressive; legs much more affected than arms; pes cavus |
| LESS COMMON | Primary lateral sclerosis | Rare (2-3% of motor neuron disease spectrum) | Pure upper motor neuron syndrome; very slow progression; no lower motor neuron signs; may evolve to ALS |
| UNCOMMON | Motor neuron disease (amyotrophic lateral sclerosis) | Incidence 2-3 per 100,000 per year | Mixed upper and lower motor neuron signs; fasciculations; progressive weakness; bulbar symptoms; normal sensation |
| UNCOMMON | Spinal cord tumor (primary or metastatic) | Varies by population | Progressive myelopathy; back pain (often worse lying down); sensory level; sphincter dysfunction |
| UNCOMMON | Subacute combined degeneration (vitamin B12 deficiency) | Increasingly recognized | Combined posterior column and corticospinal tract involvement; peripheral neuropathy; macrocytic anemia may be absent |
| UNCOMMON | Parasagittal meningioma | Rare but treatable | Progressive leg weakness (may be bilateral); seizures; headache; compresses motor cortex for legs |
| UNCOMMON | HTLV-1 associated myelopathy (tropical spastic paraparesis) | Endemic areas (Caribbean, Japan, Africa) | Slowly progressive spastic paraparesis; bladder dysfunction; from endemic area or blood transfusion |
| UNCOMMON | Neuromyelitis optica spectrum disorder | Rare | Severe transverse myelitis (often longitudinally extensive); optic neuritis; aquaporin-4 or MOG antibodies |
| UNCOMMON | Adrenomyeloneuropathy | Rare X-linked disorder | Progressive spastic paraparesis in young men; adrenal insufficiency; elevated very long chain fatty acids |
Anatomical Approach to Spasticity
Cerebral (Brain) Lesions
Stroke (ischemic or hemorrhagic)
Traumatic brain injury
Brain tumor (primary or metastatic)
Cerebral palsy
Multiple sclerosis (cerebral plaques)
Parasagittal meningioma
Hypoxic-ischemic encephalopathy
Brainstem Lesions
Brainstem stroke
Multiple sclerosis (brainstem plaques)
Brainstem tumor
Central pontine myelinolysis
Progressive supranuclear palsy (rigidity predominant)
Cervical Spinal Cord
Cervical spondylotic myelopathy
Cervical spinal cord injury
Multiple sclerosis (spinal plaques)
Spinal cord tumor
Syringomyelia
Transverse myelitis
Motor neuron disease
Thoracic/Lumbar Spinal Cord
Thoracic cord injury
Hereditary spastic paraplegia
Multiple sclerosis
HTLV-1 myelopathy
Subacute combined degeneration
Spinal cord tumor
Spinal dural arteriovenous fistula
Differential Diagnosis: Stiffness NOT Due to Spasticity
Not all stiffness is spasticity. Consider these alternative diagnoses when the clinical features do not fit typical upper motor neuron spasticity:
| Condition | Key Distinguishing Features | How to Differentiate |
|---|---|---|
| Parkinson disease (rigidity) | Lead-pipe or cogwheel rigidity; not velocity-dependent; bradykinesia; rest tremor; postural instability | Rigidity is constant through range; no hyperreflexia; look for other parkinsonian features |
| Dystonia | Sustained or intermittent muscle contractions causing abnormal postures; may be task-specific; sensory tricks | Postures may be unusual; may have null point; often improves with sensory trick (geste antagoniste) |
| Stiff person syndrome | Episodic severe spasms; axial rigidity; startle-induced spasms; autoimmune associations (diabetes, thyroid) | Anti-GAD65 antibodies; EMG shows continuous motor unit activity; dramatic response to benzodiazepines |
| Neuromyotonia (Isaacs syndrome) | Muscle stiffness with continuous muscle fiber activity; myokymia; hyperhidrosis; may be paraneoplastic | EMG shows neuromyotonic discharges; anti-CASPR2 or anti-LGI1 antibodies; may respond to carbamazepine |
| Contracture (non-neural) | Fixed joint limitation; not velocity-dependent; no change with anesthesia or nerve block | No catch and release; passive range limited at all speeds; does not improve with antispasticity medications |
| Myotonia | Delayed muscle relaxation after contraction; grip myotonia; percussion myotonia; worsens in cold | EMG shows myotonic discharges; improves with repeated movement (warm-up phenomenon) |
| Tetanus | Generalized muscle rigidity; risus sardonicus; opisthotonus; history of wound; unvaccinated | Clinical diagnosis; no velocity dependence; severe spasms triggered by stimuli |
| Neuroleptic malignant syndrome | Severe rigidity; hyperthermia; altered mental status; autonomic instability; recent neuroleptic exposure | Lead-pipe rigidity; elevated creatine kinase; recent medication change; medical emergency |
| Serotonin syndrome | Hypertonicity; clonus; hyperthermia; agitation; recent serotonergic medication | May have clonus (particularly lower limbs); hyperreflexia; tremor; medication history |
Drug-Induced Worsening of Spasticity or Mimics
| Drug or Drug Class | Mechanism | Characteristics | Management |
|---|---|---|---|
| Selective serotonin reuptake inhibitors (SSRIs) | Serotonin enhances motor neuron excitability via persistent inward currents | May worsen existing spasticity; can cause serotonin syndrome with hypertonicity | Consider alternative antidepressant; reduce dose if possible |
| Baclofen withdrawal | Rebound loss of GABAergic inhibition; particularly severe with intrathecal pump failure | Severe spasticity, hyperthermia, seizures, rhabdomyolysis—potentially fatal | Emergency: restore baclofen; supportive care; benzodiazepines |
| Benzodiazepine withdrawal | Loss of GABAergic inhibition | Increased spasticity, spasms, anxiety, potential seizures | Gradual taper; reinstate if needed |
| Antipsychotics (neuroleptics) | Dopamine blockade can cause rigidity and acute dystonic reactions | Neuroleptic malignant syndrome; acute dystonia; parkinsonism with rigidity | Discontinue offending agent; supportive care; anticholinergics for dystonia |
| Metoclopramide | Dopamine antagonist | Can cause acute dystonia, tardive syndromes, or drug-induced parkinsonism | Discontinue; avoid in patients with movement disorders |
| Lithium | Multiple mechanisms including effects on ion channels | Can worsen spasticity; causes tremor; may cause neurotoxicity with rigidity | Monitor levels; consider alternative mood stabilizer |
| Stimulants (amphetamines, methylphenidate) | Increased catecholaminergic activity | May increase muscle tone and spasticity | Use cautiously in spasticity patients; consider alternatives |
Quick Reference: “If You See This, Think This”
| Clinical Clue | Think This First | Next Step |
|---|---|---|
| Acute hemiplegia with facial weakness | Stroke | Urgent brain imaging; stroke protocol |
| Progressive spastic paraparesis with sensory level | Spinal cord compression | Urgent MRI spine; neurosurgical referral |
| Young adult with relapsing neurological symptoms | Multiple sclerosis | MRI brain and spine with contrast; lumbar puncture |
| Slowly progressive spastic paraparesis with family history | Hereditary spastic paraplegia | Genetic testing; family pedigree |
| Older adult with neck pain, hand clumsiness, gait difficulty | Cervical spondylotic myelopathy | MRI cervical spine; surgical evaluation |
| Mixed upper and lower motor neuron signs with fasciculations | Motor neuron disease (ALS) | EMG/nerve conduction studies; exclude mimics |
| Spasticity with peripheral neuropathy and macrocytosis | Subacute combined degeneration (B12 deficiency) | Check vitamin B12, methylmalonic acid, homocysteine |
| Sudden worsening in patient with spinal cord injury | Noxious stimulus (UTI, constipation, pressure injury) | Systematic search for treatable cause |
| Truncal rigidity with startle-induced spasms | Stiff person syndrome | Anti-GAD65 antibodies; EMG |
| Bilateral leg weakness with seizures | Parasagittal meningioma | MRI brain with contrast |
6. Diagnostic Investigations
A stepwise, targeted approach guided by clinical pattern and suspicion
Investigation of spasticity is guided by whether the cause is known or unknown, and by the clinical pattern (hemiplegic suggesting cerebral pathology, paraplegic suggesting spinal pathology). In patients with established diagnoses (e.g., prior stroke, known spinal cord injury), investigation focuses on identifying treatable causes of worsening. In patients without a known cause, systematic investigation aims to localize and identify the underlying pathology.
Baseline Investigations for All Patients with Unexplained Spasticity
| Investigation | Purpose | What to Look For | Practical Points |
|---|---|---|---|
| Complete blood count | Screen for anemia, infection, malignancy | Macrocytic anemia (B12 deficiency); leukocytosis (infection); pancytopenia | Macrocytosis may precede anemia in B12 deficiency |
| Comprehensive metabolic panel | Assess renal and hepatic function; electrolytes | Renal failure, hepatic dysfunction, electrolyte abnormalities | Important for medication dosing and ruling out metabolic causes |
| Vitamin B12 level | Screen for subacute combined degeneration | Low B12 (less than 200 pg/mL is deficient; 200-400 pg/mL may be insufficient) | Check methylmalonic acid and homocysteine if B12 is borderline |
| Thyroid function tests | Thyroid disease can affect muscle tone | Hypothyroidism (myopathy, delayed relaxation); hyperthyroidism (hyperreflexia) | May contribute to muscle symptoms |
| Erythrocyte sedimentation rate and C-reactive protein | Screen for inflammatory or infectious process | Elevated in inflammatory myelopathy, infection, malignancy | Non-specific but useful as screening tests |
| Urinalysis and urine culture | Screen for urinary tract infection (common trigger for worsening spasticity) | Pyuria, bacteriuria, nitrites | Essential in spinal cord injury patients with worsening spasticity |
Neuroimaging
Choosing the Right Imaging Study
MRI is the imaging modality of choice for evaluating spasticity, as it best visualizes the brain and spinal cord parenchyma. CT is useful in acute settings when MRI is unavailable or contraindicated, and for bony pathology.
| Clinical Pattern | Imaging Study | What to Look For | Key Points |
|---|---|---|---|
| Hemiplegic pattern | MRI brain with and without contrast | Stroke (acute or chronic), tumor, demyelinating lesion, structural abnormality | Include diffusion-weighted imaging for acute stroke; contrast for tumor or inflammation |
| Paraplegic or quadriplegic pattern | MRI entire spine with and without contrast | Cord compression, demyelinating lesions, tumor, syrinx, vascular malformation | Image entire spine; compressive lesions may be distant from clinical level |
| Cervical myelopathy suspected | MRI cervical spine | Disc herniation, spondylotic changes, cord signal change, cord compression | T2 hyperintensity in cord indicates myelomalacia |
| Multiple sclerosis suspected | MRI brain and spine with contrast | Periventricular, juxtacortical, infratentorial, and spinal cord lesions; enhancing lesions indicate active disease | Apply McDonald criteria; look for dissemination in space and time |
| Progressive bilateral leg weakness with seizures | MRI brain with contrast | Parasagittal mass (meningioma compressing leg motor areas) | Include coronal views to assess parasagittal region |
Targeted Investigations by Suspected Etiology
If Suspecting Multiple Sclerosis
First-Line Tests
- MRI brain and spine with gadolinium: Look for lesions disseminated in space and time; periventricular, juxtacortical, infratentorial, spinal cord
- Lumbar puncture: Cerebrospinal fluid analysis for oligoclonal bands (present in greater than 95% of MS), elevated IgG index
Second-Line Tests
- Visual evoked potentials: Prolonged P100 latency suggests prior optic neuritis
- Optical coherence tomography: Retinal nerve fiber layer thinning
- Aquaporin-4 and MOG antibodies: To exclude neuromyelitis optica spectrum disorder
If Suspecting Spinal Cord Compression
First-Line Tests
- MRI entire spine with and without contrast: Identifies level and nature of compression (disc, tumor, abscess, hematoma)
- Plain radiographs: May show vertebral collapse, alignment abnormalities
Additional Tests
- CT myelography: If MRI contraindicated or for surgical planning
- Biopsy: If tumor identified and tissue diagnosis needed
- Staging workup: If metastatic disease suspected (CT chest/abdomen/pelvis, bone scan, PET)
If Suspecting Motor Neuron Disease
First-Line Tests
- Electromyography (EMG) and nerve conduction studies: Widespread denervation in multiple regions; normal sensory studies; fasciculation potentials
- MRI brain and cervical spine: Exclude structural lesions mimicking motor neuron disease
Tests to Exclude Mimics
- Anti-GM1 antibodies: Multifocal motor neuropathy
- Paraneoplastic antibodies: If atypical features
- Creatine kinase: Often mildly elevated in ALS
- Genetic testing: If family history (SOD1 and other genes)
If Suspecting Hereditary Spastic Paraplegia
First-Line Tests
- MRI brain and spine: Usually normal or shows thin spinal cord; excludes structural lesions
- Genetic testing: SPG4 (spastin) is most common autosomal dominant form; SPG7, SPG3A also common; gene panel or exome sequencing
Additional Investigations
- Very long chain fatty acids: Elevated in adrenomyeloneuropathy (X-linked)
- Nerve conduction studies: May show additional peripheral neuropathy in some HSP subtypes
- White blood cell enzymes: For leukodystrophies if suspected
If Suspecting Stiff Person Syndrome
First-Line Tests
- Anti-GAD65 antibodies (serum and CSF): Present in approximately 80% of cases; very high titers support diagnosis
- EMG: Continuous motor unit activity in agonist and antagonist muscles simultaneously
Additional Tests
- Anti-amphiphysin antibodies: If paraneoplastic form suspected
- Anti-glycine receptor antibodies: In progressive encephalomyelitis with rigidity and myoclonus (PERM)
- Malignancy screening: CT chest/abdomen/pelvis if paraneoplastic antibodies positive
- Blood glucose, HbA1c: Diabetes commonly associated
Cerebrospinal Fluid Analysis
Lumbar puncture is indicated when inflammatory, infectious, or neoplastic causes are suspected.
| CSF Finding | Suggests | Additional Tests |
|---|---|---|
| Oligoclonal bands (CSF-specific) | Multiple sclerosis, other inflammatory CNS disease | Paired serum sample; IgG index |
| Elevated protein with normal cells | Spinal cord compression, Guillain-Barré syndrome (if weakness present) | MRI spine if not done |
| Pleocytosis (elevated white cells) | Infection, inflammation (transverse myelitis, MS relapse), malignancy | Cytology, cultures, viral PCR studies |
| Malignant cells | Leptomeningeal carcinomatosis | Cytology, flow cytometry, staging workup |
| Positive VDRL | Neurosyphilis | Serum treponemal antibodies for confirmation |
| HTLV-1 antibodies | HTLV-1 associated myelopathy | Confirm with serum HTLV-1 antibodies; PCR |
Electrophysiological Studies
| Test | When to Order | What It Shows | Key Findings |
|---|---|---|---|
| EMG and nerve conduction studies | Suspected motor neuron disease, peripheral neuropathy component, neuromyotonia | Lower motor neuron involvement, denervation, motor unit changes | ALS: widespread denervation, fasciculations; neuromyotonia: continuous motor unit activity |
| Visual evoked potentials | Suspected multiple sclerosis; evidence of optic pathway involvement | Conduction velocity through optic pathways | Prolonged P100 latency suggests demyelination |
| Somatosensory evoked potentials | Localization of spinal cord lesion; subclinical cord involvement | Conduction through dorsal columns | Prolonged latencies at level of lesion |
| Motor evoked potentials (transcranial magnetic stimulation) | Assessment of corticospinal tract function | Conduction through motor pathways | Prolonged central motor conduction time in upper motor neuron lesions |
Investigating Sudden Worsening of Established Spasticity
Systematic Search for Noxious Stimuli
In patients with known causes of spasticity (especially spinal cord injury), sudden worsening should trigger investigation for reversible causes before escalating treatment:
- Urinalysis and urine culture: Urinary tract infection is the most common cause
- Abdominal radiograph: Constipation or fecal impaction
- Skin examination: Pressure injuries, ingrown toenails
- Review of equipment: Tight orthoses, catheter straps, positioning
- Radiographs of limbs: Occult fracture (especially if osteoporotic)
- Doppler ultrasound: Deep vein thrombosis
- Review medications: Recent changes, missed doses of antispasticity medication
- If intrathecal baclofen pump: Check pump function, catheter integrity, refill status
Role of Treatment Response in Diagnosis
Diagnostic Treatment Trials
In some cases, response to specific treatments can support a diagnosis:
- Dramatic response to benzodiazepines: Supports stiff person syndrome (though other causes also respond)
- Response to levodopa: Suggests dystonia rather than spasticity (dopa-responsive dystonia)
- Nerve block distinguishes spasticity from contracture: If stiffness resolves with local anesthetic block of the nerve, the component is neural (spasticity); if it persists, it is non-neural (contracture)
- Resolution with treating infection: Confirms noxious stimulus as cause of worsening
Investigation Pathway Summary
Approach to Investigation Based on Clinical Scenario:
- Known cause with stable spasticity: No routine investigation needed; investigate if worsening or new symptoms
- Known cause with sudden worsening: Search for noxious stimuli (urinalysis, examination for skin issues, review medications)
- Unknown cause with hemiplegic pattern: MRI brain → if normal, consider MRI cervical spine → baseline bloods
- Unknown cause with paraplegic pattern: MRI entire spine → baseline bloods including B12 → consider lumbar puncture if inflammatory cause suspected
- Unknown cause with mixed UMN/LMN signs: EMG/NCS → MRI brain and spine → consider genetic testing for motor neuron disease
- Suspected stiff person syndrome: Anti-GAD65 antibodies → EMG → glucose/HbA1c → malignancy screening if paraneoplastic suspected
7. Pattern Recognition and Clinical Decision-Making
Practical algorithms and decision pathways for evaluating and managing spasticity
Step 1: Is This Urgent?
| Clinical Scenario | Urgency Level | Immediate Action |
|---|---|---|
| Acute paraplegia or quadriplegia with sensory level | EMERGENT | Immediate MRI spine; neurosurgical consultation; consider high-dose steroids if inflammatory |
| Suspected spinal cord compression (back pain, progressive weakness, bladder dysfunction) | EMERGENT | Urgent MRI spine within hours; neurosurgical evaluation; dexamethasone if tumor suspected |
| Fever with back pain and new neurological deficits | EMERGENT | MRI spine; blood cultures; empiric antibiotics; neurosurgical consultation for possible epidural abscess |
| Suspected baclofen withdrawal (severe spasticity, hyperthermia, altered mental status) | EMERGENT | ICU admission; restore baclofen (oral or intrathecal); high-dose benzodiazepines; check pump if intrathecal |
| Acute stroke with new hemiplegia | EMERGENT | Stroke protocol; CT head; consider thrombolysis or thrombectomy if within window |
| Sudden worsening of spasticity in spinal cord injury patient | URGENT | Systematic search for noxious stimulus; urinalysis; skin examination; review medications |
| Progressive myelopathy over days to weeks | URGENT | MRI spine within 24-48 hours; expedited neurology referral |
| New spasticity without clear cause | URGENT | Neurology referral; MRI brain and/or spine based on pattern; baseline investigations |
| Chronic stable spasticity affecting function | ROUTINE | Outpatient neurology or rehabilitation referral; optimize current management |
| Established spasticity—routine follow-up | ROUTINE | Regular monitoring; adjust medications as needed; physical therapy; prevention of complications |
Step 2: Classify by Pattern
Hemiplegic Pattern
Suggests: Cerebral lesion (contralateral hemisphere)
Proceed to: Brain-focused evaluation
Key investigation: MRI brain
Paraplegic Pattern
Suggests: Thoracic or upper lumbar spinal cord lesion
Proceed to: Spinal cord evaluation
Key investigation: MRI thoracic and lumbar spine
Quadriplegic Pattern
Suggests: Cervical spinal cord or bilateral cerebral lesion
Proceed to: Cervical spine evaluation first
Key investigation: MRI cervical spine; consider brain imaging
Step 3: Follow the Appropriate Algorithm
Algorithm A: New Onset Spasticity—Unknown Cause
| Clinical Scenario | Most Likely Diagnosis | Action |
|---|---|---|
| Acute hemiplegia, vascular risk factors, sudden onset | Stroke | Urgent CT/MRI brain; stroke protocol; neurology consultation |
| Progressive paraparesis, sensory level, bladder symptoms | Spinal cord lesion (compression, myelitis, tumor) | Urgent MRI entire spine; neurosurgery if compressive |
| Relapsing neurological symptoms, young adult, visual symptoms | Multiple sclerosis | MRI brain and spine; lumbar puncture; neurology referral |
| Slowly progressive leg stiffness, family history, pes cavus | Hereditary spastic paraplegia | MRI spine (usually normal); genetic testing; genetics referral |
| Older adult, neck pain, hand clumsiness, gait difficulty | Cervical spondylotic myelopathy | MRI cervical spine; spine surgery evaluation if significant compression |
| Mixed upper and lower motor neuron signs, fasciculations, no sensory loss | Motor neuron disease | EMG/NCS; MRI to exclude mimics; neurology referral |
| Truncal rigidity, startle-induced spasms, diabetes | Stiff person syndrome | Anti-GAD65 antibodies; EMG; trial of benzodiazepines |
Algorithm B: Established Spasticity—Worsening
| Clinical Scenario | Most Likely Cause | Action |
|---|---|---|
| Spinal cord injury patient with sudden increase in spasticity | Noxious stimulus below lesion level | Urinalysis (UTI); examine skin (pressure injury); check for constipation; review equipment |
| Patient on intrathecal baclofen with severe worsening, fever | Pump malfunction or catheter problem | Emergency: check pump; plain radiograph for catheter; restore baclofen; ICU if severe |
| MS patient with gradual worsening over months | Disease progression or new relapse | MRI brain and spine; consider relapse treatment if acute; optimize disease-modifying therapy |
| Post-stroke patient with increasing stiffness over time | Natural evolution; developing contracture | Increase antispasticity treatment; intensify stretching; consider botulinum toxin |
| Worsening after starting new medication | Drug-induced worsening | Review recent medication changes (SSRIs, stimulants); consider discontinuing culprit |
| Worsening with new back pain or neurological signs | New pathology (syrinx, tethered cord, tumor) | Repeat MRI spine; neurosurgical evaluation if new lesion |
Step 4: Treatment Decision Framework
Key Questions Before Initiating Treatment:
- Is the spasticity causing problems? If spasticity is not causing functional impairment, pain, or care difficulties, treatment may not be needed
- Is the patient using spasticity functionally? Some patients use extensor tone to stand or transfer—reducing it may worsen function
- Is this spasticity or contracture? Contracture will not respond to antispasticity medications
- Is the distribution focal, regional, or generalized? This determines treatment approach
- What are the treatment goals? Define specific, measurable goals (reduce pain, improve hygiene access, improve gait)
Treatment Selection by Distribution
| Distribution | First-Line Approach | Second-Line Options | Notes |
|---|---|---|---|
| Focal (one limb or muscle group) | Botulinum toxin injections; physical therapy; orthoses | Phenol or alcohol nerve blocks; surgical lengthening if contracture | Avoid systemic medications for focal spasticity—more side effects, less targeted benefit |
| Regional (hemibody or paraparesis) | Combination: botulinum toxin for priority muscles + oral medication if needed | Intrathecal baclofen if lower limbs predominant; systemic medications | Often requires multimodal approach |
| Generalized (all four limbs) | Oral antispasticity medications (baclofen, tizanidine); physical therapy | Intrathecal baclofen; combination oral medications | Start low, titrate slowly; monitor for sedation and weakness |
“What Do I Do If…” Decision Reference
| Clinical Situation | Immediate Action | Next Step |
|---|---|---|
| Patient has acute paraplegia and back pain | Treat as spinal cord compression until proven otherwise; urgent MRI | Neurosurgical consultation; dexamethasone if tumor suspected |
| Spasticity is affecting hygiene and caregiver ability to provide care | Prioritize hip adductor spasticity; consider botulinum toxin to adductors | Positioning assessment; seating evaluation; consider intrathecal baclofen if severe |
| Patient has painful nocturnal spasms disrupting sleep | Start or increase baclofen or tizanidine; consider evening dosing; add benzodiazepine at night if needed | Address contributing factors (full bladder, positioning); review for noxious stimuli |
| Oral medications cause excessive sedation before effective | Slow titration; try alternative agent; consider focal treatment with botulinum toxin | If generalized spasticity and oral agents not tolerated, consider intrathecal baclofen evaluation |
| Botulinum toxin effect wearing off too quickly | Review injection technique and dose; consider antibody formation | Switch to different botulinum toxin formulation; consider adding oral agent; refer for intrathecal baclofen if appropriate |
| Spasticity reduced but patient function is worse | Assess whether spasticity was being used functionally; check for unmasked weakness | Reduce antispasticity treatment; focus on strengthening; redefine treatment goals |
| Patient with intrathecal baclofen pump and fever | Rule out pump pocket infection; check for meningitis; evaluate for systemic infection | Infectious disease consultation; may need pump removal if infected |
| Patient cannot distinguish spasticity from contracture | Perform careful examination with slow passive stretch; consider nerve block | Diagnostic nerve block: if stiffness resolves, it is spasticity; if persists, it is contracture requiring different approach |
Troubleshooting Refractory Spasticity
Ask These Questions When Spasticity Is Not Responding to Treatment
- Is the diagnosis correct? Could this be rigidity, dystonia, or contracture rather than spasticity?
- Has a noxious stimulus been excluded? UTI, constipation, pressure injury, occult fracture?
- Is the medication dose adequate? Many patients are undertreated due to side effect concerns
- Is medication compliance good? Missed doses can cause rebound spasticity
- Is the treatment targeting the right muscles? Botulinum toxin must be injected into the correct muscles
- Has secondary contracture developed? Contracture does not respond to antispasticity medications
- Are there multiple contributing factors? Spasticity often has multiple aggravating factors that need to be addressed simultaneously
- Should the patient be evaluated for intrathecal baclofen? Consider for severe, generalized spasticity not responding to oral agents
When to Refer
Refer to Neurology
- New onset spasticity without clear cause
- Progressive neurological symptoms
- Diagnostic uncertainty
- Suspected inflammatory or genetic condition
- Botulinum toxin treatment needed
Refer to Rehabilitation Medicine
- Comprehensive spasticity management program needed
- Evaluation for intrathecal baclofen pump
- Complex seating and positioning needs
- Functional goal setting and therapy coordination
- Orthotic evaluation
8. Clinical Pearls and Pitfalls
Practical wisdom — learn from successes and avoid common mistakes
Must-Know Clinical Pearls
Velocity dependence is the key: True spasticity increases with faster passive movement. If resistance is constant regardless of speed, consider rigidity, dystonia, or contracture instead.
Always search for noxious stimuli: In patients with established spasticity (especially spinal cord injury), any sudden worsening should trigger a systematic search for urinary tract infection, constipation, pressure injuries, ingrown toenails, or other noxious stimuli before escalating medications.
Weakness often causes more disability than spasticity: The “negative” features of upper motor neuron syndrome (weakness, loss of dexterity, fatigue) frequently impact function more than the spasticity itself. Reducing spasticity may unmask this underlying weakness.
Some patients use spasticity functionally: Always ask whether the patient relies on their spasticity for standing, transfers, or other activities. Treating spasticity aggressively in these patients may worsen their function.
A normal examination does not exclude serious pathology: Early myelopathy may present with minimal findings. If the history is suspicious, proceed with imaging even if the examination is relatively normal.
Brisk jaw jerk localizes the lesion above the foramen magnum: If reflexes are brisk in all four limbs and the jaw jerk is also brisk, the lesion is in the brain or high brainstem, not the spinal cord.
Match treatment to distribution: Focal spasticity responds best to botulinum toxin; generalized spasticity requires systemic treatment. Using oral medications for purely focal spasticity exposes the patient to unnecessary systemic side effects.
Define specific treatment goals: Vague goals like “reduce spasticity” lead to treatment failures. Instead, set measurable functional goals: “improve caregiver’s ability to perform perineal hygiene” or “reduce painful spasms from 10 to fewer than 3 per day.”
Critical Pitfalls to Avoid
Mistaking contracture for spasticity: Contracture is fixed, non-neural resistance that does not respond to antispasticity medications. Test by moving the limb slowly—if resistance is still present at very slow speeds, contracture has likely developed. A diagnostic nerve block can distinguish the two.
Abrupt baclofen discontinuation: Sudden withdrawal of baclofen—especially intrathecal baclofen—can cause a life-threatening syndrome with severe rebound spasticity, hyperthermia, rhabdomyolysis, and multiorgan failure. Always taper gradually and have emergency protocols for pump malfunction.
Missing spinal cord compression: Progressive spasticity with sensory level or bladder dysfunction requires urgent spinal imaging. Delayed diagnosis of compressive myelopathy leads to irreversible neurological injury.
Confusing spasticity with rigidity: Rigidity (seen in Parkinson disease) is not velocity-dependent and has a “lead-pipe” or “cogwheel” quality. The treatment approach is completely different—antispasticity medications do not help rigidity.
Treating spasticity that isn’t causing problems: Not all spasticity requires treatment. If the patient is not experiencing functional limitations, pain, or care difficulties, and is not at risk for contracture, observation may be appropriate.
Forgetting to look at the feet: An ingrown toenail or tight shoe is an easily correctable cause of worsening spasticity in spinal cord injury patients, yet is frequently overlooked during evaluation.
Ignoring the “inverted reflex”: When tapping the biceps or brachioradialis reflex produces finger flexion instead of the expected muscle contraction, this indicates a cervical cord lesion at C5-C6—a critical localizing sign that should not be missed.
Under-dosing or giving up too quickly: Oral antispasticity medications often require gradual titration to effective doses. Many patients are undertreated because of premature concern about side effects or insufficient time for dose optimization.
Key Takeaways
- Spasticity is velocity-dependent: The hallmark is increased resistance to rapid passive movement with a “catch and release” quality—this distinguishes it from rigidity, dystonia, and contracture.
- Spasticity is one component of a larger syndrome: The upper motor neuron syndrome includes both positive features (spasticity, hyperreflexia, spasms) and negative features (weakness, loss of dexterity)—both must be addressed.
- Pattern determines localization: Hemiplegic pattern suggests cerebral lesion; paraplegic pattern suggests spinal cord lesion; quadriplegic pattern suggests cervical cord or bilateral brain pathology.
- Acute spinal cord symptoms are emergencies: Progressive weakness with sensory level or bladder dysfunction requires urgent imaging and intervention to prevent permanent injury.
- Noxious stimuli are the most common cause of acute worsening: In patients with established spinal cord injury, always search for urinary tract infection, constipation, pressure injuries, and other treatable triggers.
- Treatment should match the distribution: Focal spasticity is best treated with botulinum toxin; generalized spasticity requires oral medications or intrathecal baclofen.
- Set specific, measurable treatment goals: Success should be defined by functional improvement (better hygiene access, reduced spasm frequency, improved gait), not just reduced tone on examination.
- Some spasticity may be beneficial: Patients may use spasticity for standing transfers or to support weak limbs—always assess functional impact before treating aggressively.
- Contracture is not spasticity: Non-neural soft tissue shortening does not respond to antispasticity medications and requires different management (stretching, serial casting, surgical release).
- Never stop baclofen abruptly: Baclofen withdrawal—especially from intrathecal pumps—can be life-threatening. Always taper gradually and have emergency protocols in place.
Quick Reference Algorithm
Systematic Approach to Spasticity:
- Confirm spasticity: Velocity-dependent increase in tone with clasp-knife quality; distinguish from rigidity, dystonia, contracture
- Assess urgency: Acute onset with red flags (sensory level, bladder dysfunction, back pain, fever) requires urgent imaging
- Identify pattern: Hemiplegic (brain), paraplegic (thoracic/lumbar cord), quadriplegic (cervical cord or bilateral brain)
- Establish cause: If unknown, investigate with MRI of appropriate region, baseline blood tests, and additional studies based on clinical suspicion
- Assess for worsening triggers: In established spasticity, search for noxious stimuli (UTI, constipation, skin breakdown, equipment issues)
- Evaluate functional impact: Determine if spasticity is causing problems; identify specific goals for treatment
- Select treatment approach: Match treatment to distribution—focal (botulinum toxin), regional (combination), generalized (oral medications, intrathecal baclofen)
- Monitor and adjust: Reassess response to treatment; modify approach based on outcomes; address complications (contracture prevention)