Spasticity is usually caused by damage to the nerve pathways in the brain or spinal cord that control muscle movement. It can result from spinal cord injury, multiple sclerosis, cerebral palsy, stroke, brain or head trauma, amyotrophic lateral sclerosis, hereditary spastic paraplegias, and metabolic diseases such as adrenoleukodystrophy, phenylketonuria, and Krabbe disease. Spasticity affects more than 12 million people worldwide, including approximately 80% of people with cerebral palsy and 80% of people with multiple sclerosis. A team approach is important in the management of spasticity, and may involve exercise, physical therapy, medication, or surgery.