Spasticity is an abnormality of muscle tone that commonly occurs after an injury to the brain or spinal cord. Damage to the nervous system pathways controlling muscle activity leads to involuntary and excessive muscle shortening (called contraction) in response to rapid muscle stretch. Normally, muscles are able to accommodate to the voluntary and involuntary stretching that occurs in the course of daily life. Spastic muscles, however, react against such stretch with excessive contraction, which may continue for a prolonged period of time.

Spasticity, experienced by the patient as a feeling of increased stiffness, occurs in approximately 20% of individuals after a stroke, either quickly or in a delayed manner. The location and extent of the damage in the brain influences the distribution and severity of the spasticity. The pattern of spasticity after most strokes is fairly predictable. The upper arm tends to be pulled toward the chest wall, accompanied by flexion at the elbow, wrist and fingers. This flexed posture often is assumed automatically during walking, when sneezing or coughing, or in response to any irritation of the limb. In the leg, spasticity may produce stiffening of the limb in extension, while the foot may turn down and in. Spasticity may appear also in muscles that support the trunk, as well as in those that produce speech and coordinate swallowing. Other movement disorders may be associated with spasticity, such as sustained involuntary postures of a limb or the trunk (dystonia), rapid beating of the foot when the ankle is stretched (clonus), and involuntary leg flexion or extension.

Spasticity may offer some benefits. In a person with significant trunk muscle weakness after a stroke, spasticity in these weakened muscles may assist that individual in maintaining a sitting or standing posture. Similarly, a person with severe leg weakness may take advantage of the involuntary leg extension which stiffens the leg, and thus may allow walking.

Spasticity may also cause problems, such as pain, muscle contracture leading to joint deformity, skin breakdown, hygiene difficulties, trouble moving in bed, difficulty with transfers, poor seating position, impaired ability to walk, and diminished functional independence. Contractures occur when there is loss of joint motion due to structural changes in the muscles, ligaments and tendons surrounding the joint. Shortening and stiffness of the soft tissues makes the joint resistant to stretching and prevents normal movement. Early in contracture formation, much of the joint stiffness may be due to spasticity. Treatments to control this, and to stretch the stiffening tissues, often are effective in preventing further loss of motion and restoring joint function. However, if untreated, significant changes may occur in muscles, ligaments and tendons, and the contracture may become fixed. In such cases, surgery may be needed to relieve the deformity.

Spastic muscles and joint contractures can prevent access to the palm, armpit or groin, thus interfering with cleanliness and increasing the risk of skin breakdown. Bowel and bladder care may become more difficult. Leg spasticity can interfere with mobility, seating, and transfers (such as from bed to wheelchair or from sitting to standing). Activities of daily living, such as dressing, eating and grooming, also may be impaired by spasticity. The combination of spasticity, contracture, pain, and weakness may be associated with depression and impaired sexual activity.

The mere presence of spasticity is not in itself an indication for treatment. If the spasticity is functionally useful, such as assisting in walking or for support of the trunk, treatment which diminishes the spasticity may lead to a decline in independence. Even when it appears that spasticity is interfering with function, its removal may not necessarily decrease the disability because of underlying muscle weakness and lack of muscle control. Treatment of spasticity is usually indicated if there is significant interference with function, risk of progressive deformity, contribution to skin ulceration, pain, social isolation secondary to cosmetic concerns, interference with hygiene, interference with sexual activity, significant contribution to caretaker burden, and problems with fit into a needed brace or splint (orthosis).

There are a variety of treatment options for spasticity. These include exclusive or combined use of direct physical techniques, medications, local injections, casting, splinting and surgery. Initial treatment should always involve a search for, and elimination of, any identifiable irritating stimuli. Irritants, such as skin sores, ingrown toenails, urinary tract infection, fecal impaction or an ill-fitting brace can worsen spasticity, and should be dealt with as thoroughly as possible. Physical and occupational therapy techniques may be employed to inhibit spasticity and/or to encourage the emergence of voluntary control over muscle movement. These techniques include passive and active range of motion, sustained stretching, physical measures (such as icing, vibration, tapping, electrical stimulation and acupuncture), selective strengthening of muscles, movement repatterning activities, splints (orthotics) and serial casting. Daily range of motion and stretching exercises are a mainstay of any spasticity reduction program, whose goal is to decrease the excessive muscle tone, to stretch out the soft tissues that are threatening to, or have begun to, shorten, and to prevent further joint deformity. For gains to be sustained, the home program must be performed daily for as long as the joints remain at risk for contracture (usually lifelong).

Braces or splints (orthotics) may be used to inhibit muscle activity, compensate for limb weakness, stabilize a joint, enhance movement, reduce pain and prevent joint deformities. Once a contracture has formed, it may be extremely difficult to treat. Serial casting may be attempted to reduce the deformity and avoid surgery. This involves positioning an extremity at the end of passive range of motion and casting in that position. After 7-10 days, the cast is removed, range of motion therapy is reinstituted, and then the extremity is re-casted at the new, improved angle. This may be repeated 4-5 times, followed by the daily use of a removable orthotic. When a contracture is resistant to these measures, surgery may be advised.

For widespread spasticity, oral medications may be tried. Most commonly used are tizanidine (Zanaflex®), dantrolene (Dantrium®) and baclofen (Lioresal®). They may have a variety of side effects, particularly sedation, which can limit their usefulness. Sometimes, when extreme muscle tone creates an isolated problem, such as overactive foot pointing interfering with walking, local injections of drugs such as phenol or botulinum toxin (Botox® or Myobloc®) that selectively weaken or paralyze overactive muscles can be effective. Phenol, whose effect may last 2-36 months, causes local destruction of the nerves which activate muscle. A risk is pain from sensory nerve irritation. Botulinum toxin can be effective, with onset of effect within 24-72 hours, peak effect at about 2 weeks, and benefit usually lasts up to 12 weeks. Baclofen may be delivered in very small amounts into the spinal fluid (intrathecal therapy) via an implanted pump and catheter. The pump is programmed by a hand-held device to deliver the drug at different rates and at a variety of intervals for greater control. Very small doses are used, thus avoiding many side effects, such as decreasing strength in normal muscles. Intrathecal therapy does have a number of potentially serious complications, and requires skillful medical management and vigilant patient follow-up.

There are several orthopedic and neurosurgical procedures for the treatment of spasticity. The former may be recommended for the treatment of fixed contractures or for rebalancing muscular forces across a joint to improve function. Neurosurgeons may cut nerve roots to treat severe spasticity not responsive to any other measures. None of these procedures is without significant risks.

In summary, spasticity is an abnormality of muscle tone which results from damage to the brain and/or spinal cord, and which may contribute to decreased function and diminished quality of life after stroke. A variety of fairly effective treatments are now available to manage both localized and widespread spasticity.