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Spasticity, often called tone, is an involuntary tightening of one or more muscles that develops when the nervous system’s signalling pathways are disrupted. It affects most people with spinal cord injury to some degree — understanding how it works is the first step to managing it well.
Sensory nerves carry messages from the body to the brain, which analyses them instantly and sends a response back through the motor system. When disease or injury disrupts that motor pathway, the message for movement is not received or is misread — the result is involuntary muscle tightening. People often use “spasticity” and “tone” interchangeably, but clinicians distinguish several related terms:
Muscle spasm — a random, brief involuntary contraction anyone can experience (fatigue, dehydration, low potassium)
Spasm — a single episode of involuntary contraction caused by upper motor neuron injury
Spasticity (tone) — the collective term for recurrent, involuntary muscle contractions
Hypertonia — a resting muscle so tight it becomes rigid and resists movement
Clonus
A rhythmic, beating form of spasticity, most often felt in the leg or arm, that can usually be interrupted by gently stretching the muscle.
Movement is controlled by two types of motor neurons. Which one is injured determines whether a muscle becomes spastic or flaccid.
Upper Motor Neurons (UMN)
Originate in the brain’s motor strip
Cervical & thoracic injuries typically affect these
Injury here leads to spasticity (tone)
Lower Motor Neurons (LMN)
Originate in the brainstem or spinal cord
Lumbar & sacral injuries typically affect these
Injury here leads to flaccid (limp) muscles
Mixed presentations are common. Each muscle has its own stretch reflex that keeps it lengthening and contracting normally. When a muscle is not moved — by functional use or by someone moving it for you — that reflex isn’t activated, and the muscle becomes hyperactive within itself. This is thought to be the muscle’s own way of seeking the stretch it is missing.
After traumatic SCI, muscles are flaccid for the first six weeks; spasticity typically begins afterward and can develop quickly or as a slow twitch. In SCI from disease, onset tends to track disease progression. Common symptoms include:
Increased muscle tone & overactive reflexes
Involuntary movements & recurrent spasms
Pain, tightness, and clonus
Abnormal posture, contractures, joint deformity
A Sudden Change Is a Warning Sign
A sudden increase or change in your usual spasticity pattern can signal a new complication — a UTI, a pressure injury, or (in SCI) a fluid-filled cyst called a syrinx. Because reduced sensation can mask pain, the body may instead react with autonomic dysreflexia (a dangerous spike in blood pressure). Report sudden changes to your care team promptly.
Only a neurological examination can establish whether an injury is UMN, LMN, or mixed. A full work-up typically includes:
Medical & family history, plus a full physical exam
Complete neurological exam — mental status, sensory, motor, reflexes, proprioception
EMG (electromyogram) and NCS (nerve conduction study) to test muscle and nerve function
MRI or CT scan to visually inspect the nerves
For SCI specifically, a full ASIA / AIS dermatome assessment, repeated periodically
The Modified Ashworth Scale is the most widely used measure of spasticity, performed by moving a limb passively and rating the resistance felt:
| Score | What It Means |
| 0 | No increase in muscle tone |
| 1 | Slight catch and release, or minimal resistance at the end of range |
| 2 | A catch, then minimal resistance through less than half the range |
| 3 | Marked increase through most of the range, but still easily moved |
| 4 | Considerable increase — passive movement is difficult |
| 5 | Limb is rigid in flexion or extension |
The Tardieu and Modified Tardieu Scales (often used in children) test resistance at three speeds and are considered more precise, while a goniometer measures joint range of motion to identify a contracture. Newer kinematic devices are emerging in research and larger rehabilitation centres.
Not everyone wants treatment — mild tone can help with transfers or reduce pressure-injury and clot risk. Treatment is usually sought when spasticity interferes with daily life, sleep, or bladder, bowel and breathing function. Most people need several approaches together.
Non-Prescription: Activity & Self-Calming
Regular movement feeds the muscle stretch reflex; meditation, distraction, and biofeedback help some people manage discomfort.
Oral Medications
Baclofen, clonazepam, dantrolene, diazepam or tizanidine relax muscles body-wide. Dosing is individual; never stop suddenly — taper under medical guidance to avoid withdrawal and rebound spasms.
Injectable Medications
OnabotulinumtoxinA (Botox) and abobotulinumtoxinA (Dysport) target a single muscle, typically repeated every 3–6 months. Nerve blocks act on a single nerve; phenol nerve blocks are permanent and rarely used today.
Electrical Stimulation
A portable TENS unit delivers surface impulses that interrupt spasticity or fatigue the muscle; settings vary by person.
Surgical & Implantable Options
An implanted baclofen pump delivers medication directly to the spinal fluid for severe cases. Tendon release/lengthening, and — in select paediatric cerebral palsy cases — selective dorsal rhizotomy, are reserved for when other options aren’t enough.
Gentle Stretching
Fatigues and relaxes the muscle; sharp or jerky motions make tone worse.
Casts, Splints & Braces
Hold muscles in a lengthened position to prevent contractures.
Standing Frames
Bear weight through the muscles, stretching them under load.
Strengthening
Rebalances opposing muscle groups; stronger muscles spasm less.
Cold / Heat Therapy
Use only under a therapist’s guidance if sensation is reduced.
Whole-Body Vibration
Gentle mechanical oscillation thought to lower muscle excitation.
Physiatrist / Primary Provider
Diagnoses spasticity, tracks progress, and orders therapies, medications and other treatments.
Physical Therapist
Delivers strengthening and major whole-body spasticity treatments.
Occupational Therapist
Targets local areas of concern that affect daily activities.
Rehabilitation Nurse
Helps you understand treatment options and monitors progress.
Reeve Foundation Information Specialists
Toll-free 800-539-7309 · weekdays 9am–8pm ET
Model Systems Knowledge Translation Center
msktc.org/sci/factsheets/Spasticity — plain-language spasticity fact sheetNational Institute of Neurological Disorders and Stroke (NINDS)
ninds.nih.gov — spasticity research and clinical trial listingsCraig Hospital & Shepherd Center
SCI specialty rehabilitation resources and spasticity clinics
Spasticity affects 65–75% of people with SCI, usually beginning about six weeks after traumatic injury.
A sudden change in your usual spasticity pattern deserves a call to your care team — it can be the first sign of a UTI, pressure injury, or other complication.
Treatment is not one-size-fits-all — most people combine activity, oral or injectable medication, and physical therapy techniques.
Never stop an oral spasticity medication suddenly — always taper under medical supervision.
Adapted from the Christopher & Dana Reeve Foundation Paralysis Resource Center · For educational purposes only — always consult your care team © 2026 AccessLife
