The term “spasticity” is commonly used for an upper motor neuron deficit, but it properly refers to a velocity-dependent increase in resistance to passive movement that affects different muscles to a different extent, is not uniform in degree throughout the range of a particular movement, and is commonly associated with other features of pyramidal deficit. It is often a major complication of stroke, cerebral or spinal injury, static perinatal encephalopathy, and multiple sclerosis.
Physical therapy with appropriate stretching programs is important during rehabilitation after the development of an upper motor neuron lesion and in subsequent management of the patient. The aim is to prevent joint and muscle contractures and perhaps to modulate spasticity.
Medication management is important also, but treatment may increase functional disability when increased extensor tone is providing additional support for patients with weak legs. Dantrolene weakens muscle contraction by interfering with the role of calcium. It is best avoided in patients with poor respiratory function or severe myocardial disease. Treatment is begun with 25 mg once daily, increased by 25 mg every 3 days, depending on tolerance, to a maximum of 100 mg four times daily. Side effects include diarrhea, nausea, weakness, hepatic dysfunction (that may rarely be fatal, especially in women older than 35), drowsiness, light-headedness, and hallucinations.
Baclofen is an effective medication for treating spasticity of spinal origin and painful flexor (or extensor) spasms. The maximum recommended daily oral dose is 80 mg; treatment is started with a dose of 5 or 10 mg twice daily orally and then built up gradually. Side effects include gastrointestinal disturbances, lassitude, fatigue, sedation, unsteadiness, confusion, and hallucinations. Diazepam may modify spasticity by its action on spinal interneurons and perhaps also by influencing supraspinal centers, but effective doses often cause intolerable drowsiness and vary with different patients. Tizanidine, a centrally acting alpha-2-adrenergic agonist, is as effective as these other agents and is probably better tolerated. The daily dose is built up gradually, usually to 8 mg taken three times daily. Side effects include sedation, lassitude, hypotension, and dryness of the mouth. Cannabinoids are also effective in reducing spasticity, but are associated with side effects, including dizziness, drowsiness, and fatigue.
Intramuscular injection of botulinum toxin has been used to relax targeted muscles.
In patients with severe spasticity that is unresponsive to other therapies and is associated with marked disability, intrathecal injection of phenol or alcohol may be helpful. Surgical options include implantation of an intrathecal baclofen pump, rhizotomy, or neurectomy. Severe contractures may be treated by surgical tendon release.
Spasticity may be exacerbated by decubitus ulcers, urinary or other infections, and nociceptive stimuli.