Increased involuntary muscle contraction (the opposite of hypotonicity).
Spasticity is a condition in which certain muscles are continuously contracted. This contraction causes stiffness or tightness of the muscles and may interfere with movement, speech, and manner of walking. Spasticity is usually caused by damage to the portion of the brain or spinal cord that controls voluntary movement. It may occur in association with spinal cord injury, multiple sclerosis, cerebral palsy, damage to the brain because of lack of oxygen, brain trauma, severe head injury, and metabolic diseases such as adrenoleukodystrophy, amyotrophic lateral sclerosis (Lou Gehrig's disease), and phenylketonuria. Symptoms may include hypertonicity (increased muscle tone), clonus (a series of rapid muscle contractions), exaggerated deep tendon reflexes, muscle spasms, scissoring (involuntary crossing of the legs), and fixed joints. The degree of spasticity varies from mild muscle stiffness to severe, painful, and uncontrollable muscle spasms. Spasticity can interfere with rehabilitation in patients with certain disorders, and often interferes with daily activities.
Treatment for spasticity may include such medications as baclofen, diazepam, tizanidine or clonazepam. Physical therapy regimens may include muscle stretching and range of motion exercises to help prevent shrinkage or shortening of muscles and to reduce the severity of symptoms. Surgery may be recommended for tendon release or to sever the nerve-muscle pathway.