What Is Spasticity?
Spasticity is a motor disorder characterized by a velocity-dependent increase in muscle tone — the faster the passive movement of a limb, the greater the resistance encountered. It is a component of the upper motor neuron (UMN) syndrome, resulting from lesions in the brain or spinal cord.
Spasticity is not a disease in itself but a manifestation of various neurological conditions, including stroke, multiple sclerosis, traumatic brain injury, spinal cord injury, and cerebral palsy. It is a leading cause of motor disability in neurological patients.
Paradoxically, spasticity can be both harmful and functional. In some patients, lower-limb spasticity assists in weight-bearing for standing. Treatment must be individualized and goal-oriented, focusing on improving function, reducing pain, and preventing complications.
Upper Motor Neuron Lesion
Spasticity results from lesions in the corticospinal and reticulospinal pathways, which normally modulate spinal reflexes.
Velocity-Dependent
Resistance to passive movement increases with velocity — a feature that distinguishes spasticity from rigidity.
Goal-Oriented Treatment
The goal is not to eliminate all spasticity but to improve function. Not all spasticity needs to be treated.
Pathophysiology
Spasticity results from loss of supraspinal control over spinal reflexes. Normally, the corticospinal tract and reticulospinal tract send inhibitory signals that modulate the excitability of spinal motor neurons and interneurons. When these descending pathways are injured, stretch reflexes become exaggerated.
The tonic stretch reflex is mediated by the muscle spindle: when a muscle is stretched, Ia afferents activate the alpha motor neuron, causing reflex contraction. In spasticity, this reflex is hyperactive — loss of supraspinal inhibition causes the alpha motor neuron to respond exaggeratedly to muscle spindle signals.
Over time, untreated chronic spasticity leads to secondary changes in soft tissues: muscle shortening, fibrosis, loss of sarcomeres, joint stiffness, and contractures. These biomechanical changes make resistance to movement velocity-independent, making treatment more difficult.
Causes
Spasticity can result from any lesion affecting the upper motor neuron, from the cerebral cortex to the spinal cord. The most common causes vary by age group.
MAIN CAUSES OF SPASTICITY
| CAUSE | TYPICAL PATTERN | SPASTICITY PREVALENCE |
|---|---|---|
| Stroke | Spastic hemiparesis contralateral to the lesion | 20-40% of stroke survivors |
| Multiple sclerosis | Variable — lower-limb spasticity common | 60-80% of MS patients |
| Spinal cord injury | Spasticity below the level of injury | 65-78% of spinal cord injuries |
| Cerebral palsy | Variable — diparesis, hemiparesis, or quadriparesis | 80% of spastic forms of CP |
| Traumatic brain injury | Variable depending on lesion location | 20-30% of moderate to severe TBI |
| Neurodegenerative diseases | Amyotrophic lateral sclerosis, hereditary spastic paraplegia | Variable depending on disease |
Symptoms
Spasticity manifests as part of upper motor neuron syndrome, which includes positive signs (spasticity, clonus, spasms, hyperactive reflexes) and negative signs (weakness, loss of dexterity, fatigue). The negative signs contribute most to functional disability.
Spasticity Manifestations
- 01
Increased muscle tone
Resistance to passive movement that increases with velocity. Muscles feel "hard" and tense on palpation.
- 02
Muscle spasms
Involuntary and frequently painful contractions, triggered by skin stimuli, position changes, or exertion.
- 03
Clonus
Rhythmic and repetitive contractions provoked by rapid stretching (especially at the ankle). Indicates significant spasticity.
- 04
Flexed posture (upper limb)
Typical post-stroke spastic pattern: shoulder adducted, elbow flexed, wrist flexed, fingers clenched.
- 05
Extended posture (lower limb)
Adducted hip, extended knee, plantar-flexed ankle (equinus foot). May hinder or assist gait.
- 06
Pain
Pain associated with spasms, contractures, and abnormal postures. Present in up to 70% of patients with spasticity.
- 07
Contractures
Permanent muscle shortening and joint stiffness when spasticity goes untreated.
Diagnosis and Assessment
Spasticity diagnosis is clinical, based on neurological examination. Assessment should quantify tone severity, identify the muscles involved, differentiate spasticity from fixed contractures, and establish functional impact.
🏥Spasticity Assessment
Fonte: Standardized assessment scales
Muscle Tone Scales
- 1.Modified Ashworth Scale (0-4): subjective assessment of tone during passive movement
- 2.Tardieu Scale: differentiates spasticity (velocity-dependent) from contractures (fixed)
- 3.Assessment at different stretch velocities
Functional Assessment
- 1.Goal Attainment Scaling (GAS): individualized functional goals
- 2.Penn Spasm Scale: frequency and severity of spasms
- 3.Gait assessment and upper-limb functionality
- 4.Impact on hygiene, dressing, and activities of daily living
Investigation of Aggravating Factors
Acute worsening of spasticity warrants a search for a triggering factor- 1.Urinary infections (common cause of acute worsening)
- 2.Constipation, pressure ulcers, tight clothing
- 3.Pain of any origin — reflexively aggravates spasticity
- 4.Occult fractures, deep vein thrombosis
Differential Diagnosis
Increased muscle tone has various causes beyond classic upper motor neuron spasticity. Correct distinction guides appropriate treatment.
DIAGNÓSTICO DIFERENCIAL
Differential Diagnosis
Parkinson's Disease Rigidity
Read more →- Cogwheel rigidity
- Resting tremor
- Bradykinesia
Testes Diagnósticos
- Neurological examination
- Therapeutic test with levodopa
Muscle Contracture
- Passive resistance without hyperreflexia
- Post-immobilization or trauma
- No pyramidal sign
Testes Diagnósticos
- Physical examination
- EMG
Cervical Myelopathy
- Hyperreflexia
- Clonus
- Babinski sign
- Progressive myelopathy = neurosurgery
Testes Diagnósticos
- Cervical MRI
Dystonia
Read more →- Sustained involuntary postures
- No paralysis
- Characteristic repetitive movements
Testes Diagnósticos
- Specialized neurological examination
Amyotrophic Lateral Sclerosis (ALS)
- Combination of upper and lower motor neuron
- Atrophy + hyperreflexia
- Rapid progression
- ALS = serious prognosis, urgent multidisciplinary care
Testes Diagnósticos
- EMG
- MRI
Spasticity vs. Rigidity: Fundamental Distinction
The distinction between spasticity (upper motor neuron) and rigidity (extrapyramidal) is essential because treatment is completely different. Spasticity is velocity-dependent — resistance to passive movement increases with velocity and presents the "clasp-knife phenomenon" (initial resistance that abruptly gives way). Parkinsonian rigidity stays constant throughout the range of motion regardless of velocity, presenting the "cogwheel" sign. Baclofen and botulinum toxin treat spasticity; levodopa and dopaminergic agonists treat parkinsonian rigidity — using the wrong treatment is ineffective.
Muscle contracture differs from spasticity in being a structural alteration of soft tissues — muscle shortening from fibrosis and loss of sarcomeres — without hyperreflexia or pyramidal signs. It frequently arises as a complication of untreated chronic spasticity. EMG and the Tardieu scale help differentiate neural passive resistance (velocity-dependent) from mechanical resistance (contracture, velocity-independent). Contracture requires different treatment: prolonged stretching, orthoses, and, in advanced cases, orthopedic surgery.
Cervical Myelopathy and ALS: Conditions Requiring Urgent Attention
Progressive cervical myelopathy is a relative neurosurgical emergency. Progressive lower-limb spasticity, especially with unstable gait, hyperreflexia, Babinski sign, and loss of manual dexterity, should raise suspicion of cervical cord compression. Urgent cervical MRI is mandatory. Delayed treatment can result in permanent sequelae — early surgical decompression offers better functional outcomes.
Amyotrophic lateral sclerosis presents a paradoxical combination of upper motor neuron signs (hyperreflexia, spasticity, Babinski) and lower motor neuron signs (muscle atrophy, fasciculations, weakness without hypertonia). This mixture of signs, with rapid progression and no structural cause on MRI, warrants urgent referral to a specialist neurologist. Early diagnosis allows access to disease-modifying treatments (riluzole, edaravone) and care planning.
Acute Worsening of Spasticity: Look for the Trigger
Acutely worsening spasticity in a patient with an already established diagnosis should always raise suspicion of a triggering factor. The most common causes include urinary infection (very common in patients with neurogenic bladder), constipation, pressure ulcers, tight clothing, or kidney stones in patients with spinal cord injury. Pain of any origin reflexively increases muscle tone and aggravates spasticity. Treating the trigger frequently resolves the exacerbation without needing to escalate medications.
Acupuncture can fit into the spasticity rehabilitation program as a complement to physical therapy and botulinum toxin. Experimental studies suggest modulation of the H-reflex (hyperactive in spasticity) and possible facilitation of neuroplasticity, though the clinical magnitude of these effects remains debated. Medical acupuncturists who treat patients with spasticity should be familiar with assessment of upper motor neuron syndrome to adequately contextualize the intervention.
Treatment
Treatment of spasticity is multimodal and oriented by functional goals. The approach combines physical therapy, focal treatment (botulinum toxin), and/or systemic (oral medications), depending on distribution and severity.
Physical Therapy and Rehabilitation
Cornerstone of treatment — continuousSustained stretching, adequate positioning, orthoses, strengthening exercises. Passive and active movement program. Cryotherapy and functional electrical stimulation as adjuvants.
Botulinum Toxin (Focal)
Every 12-16 weeksFirst-line for focal or multifocal spasticity. Injected into target muscles under EMG or ultrasound guidance. Effective for specific patterns: clenched fist, equinus foot, hip adductors.
Oral Medications (Systemic)
ContinuousOral baclofen: GABA-B agonist, reduces spinal excitability. Tizanidine: alpha-2 agonist, reduces excitatory-neurotransmitter release. Diazepam: potentiates GABA-A. Dantrolene: acts directly on muscle.
Advanced Therapies
Severe/generalized spasticityIntrathecal baclofen pump: direct administration into the spinal cord. Phenol/alcohol: neurolysis for longer-lasting block. Orthopedic surgery: correction of fixed deformities.
Acupuncture as Treatment
Acupuncture is one of the most studied complementary therapies for spasticity, particularly in post-stroke patients. Proposed mechanisms include modulation of spinal motor neuron excitability, possible facilitation of neuroplasticity, and regulation of the balance between excitatory and inhibitory neurotransmission — hypotheses still under investigation.
Neurophysiology studies have shown that electroacupuncture can reduce H-reflex (Hoffmann reflex) excitability and increase reciprocal inhibition between antagonist muscles. Functional MRI research also shows that acupuncture activates motor and sensory cortical areas involved in post-injury reorganization.
In clinical practice, acupuncture can be integrated into the rehabilitation program, complementing physical therapy and botulinum toxin treatment. It should be applied by professionals experienced in neurorehabilitation.
Prognosis
Spasticity prognosis depends on the underlying cause. In static conditions (stroke, spinal cord injury), spasticity tends to stabilize, though it can vary with aggravating factors. In progressive conditions (MS, ALS), spasticity can worsen as the underlying disease evolves.
Early, adequate treatment prevents complications such as contractures, pressure ulcers, and chronic pain. Continuous rehabilitation is essential for maintaining long-term function and quality of life.
Myths and Facts
Myth vs. Fact
All spasticity should be treated.
Not all spasticity is harmful. In some patients, lower-limb spasticity helps support body weight for standing and walking. Treatment should be guided by specific functional goals.
Myth vs. Fact
Post-stroke spasticity improves on its own with time.
Without adequate treatment, spasticity can progressively worsen, leading to contractures, deformities, and chronic pain. Early intervention — stretching, positioning, and, when indicated, botulinum toxin — prevents these complications.
Myth vs. Fact
Exercise worsens spasticity.
Adequate, progressive exercise prescribed by a physical therapist improves function without significantly worsening spasticity. Inactivity, by contrast, contributes to muscle shortening and functional decline.
When to Seek Help
Frequently Asked Questions
Frequently Asked Questions
No. Spasticity is not always harmful — in some patients, lower-limb spasticity assists in weight-bearing for standing and walking. Treatment is indicated when spasticity causes pain, hinders hygiene and personal care, impairs mobility or sleep, or interferes with specific functional activities. The decision to treat should always be based on clear functional goals defined with the patient.
Spasticity (upper motor neuron) is velocity-dependent — resistance to passive movement increases with velocity and presents the “clasp-knife phenomenon.” Rigidity (extrapyramidal, as in Parkinson's) is constant throughout the range of motion regardless of velocity, with the “cogwheel” sign. Treatment is completely different: baclofen and botulinum toxin for spasticity; levodopa for parkinsonian rigidity.
Without adequate treatment, post-stroke spasticity tends to progress and may lead to contractures, deformities, and chronic pain. Early treatment with physical therapy (stretching, positioning) and, when indicated, botulinum toxin, prevents these complications. Some patients have partial spontaneous improvement in the first 3-6 months post-stroke as cortical reorganization occurs, but this does not eliminate the need for active rehabilitation.
Botulinum toxin blocks acetylcholine release at the neuromuscular junction of injected muscles, reducing their ability to contract. This decreases excessive muscle tone, facilitates passive stretching, and improves function. EMG or ultrasound guides the injection to ensure precision. The effect lasts 3-4 months and should be combined with intensive physical therapy during the therapeutic window.
The intrathecal baclofen pump is a device surgically implanted in the abdomen that releases baclofen directly into the spinal CSF through a catheter. It is indicated for severe generalized spasticity when oral baclofen is insufficient or causes unacceptable side effects (excessive sedation). Intrathecal administration allows much lower doses with greater efficacy, since the drug reaches GABA-B receptors in the cord directly.
Adequate, progressive exercise prescribed by a physical therapist does not significantly worsen spasticity and generally improves function. Inactivity is harmful — it contributes to muscle shortening and functional decline. Aerobic exercise, strength training, swimming, and hippotherapy benefit patients with spasticity. Excessive exertion or exercise in very hot environments may transiently increase tone but does not cause permanent damage.
Acute worsening of spasticity in a patient with an established diagnosis should always raise suspicion of a triggering factor. The most common causes are urinary infection, constipation, pressure ulcers, ill-fitting clothing or orthoses, occult fractures, kidney stones (in spinal cord injuries), or any source of pain. Pain reflexively increases muscle tone. Identifying and treating the trigger frequently resolves the exacerbation without needing to escalate medication.
Yes. Acupuncture is one of the most studied complementary therapies for spasticity, especially post-stroke. Meta-analyses show improvement in Ashworth scores (muscle tone) and motor function as an adjuvant to conventional rehabilitation. Mechanisms include reduced H-reflex excitability (hyperactive in spasticity) and facilitation of neuroplasticity. The medical acupuncturist can integrate acupuncture into the rehabilitation program, complementing physical therapy and botulinum toxin.
Chronic untreated spasticity can progress to muscle contractures (permanent shortening), joint deformities (equinus foot, elbow flexion), pressure ulcers (from abnormal postures), skin infections, chronic pain, sleep disturbances, impaired hygiene and personal care, and deteriorated quality of life. Early, adequate treatment prevents these complications and preserves function longer.
Yes. New-onset spasticity, especially with other neurological signs (progressive weakness, muscle atrophy, dysphagia, speech changes), can indicate serious conditions such as ALS, progressive cervical myelopathy, or spinal cord tumor. In these cases, urgent neurological evaluation with MRI is mandatory. Isolated spasticity in a patient with an established neurological diagnosis (old stroke, MS, cerebral palsy) generally does not require additional urgent investigation, except for unexplained worsening.
Related Reading
Deepen your knowledge with related articles