Spasticity refers to a wide range of involuntary muscle contractions that result in muscle spasms or stiffness. Spasticity interferes with the ability to control muscle movement and usually involves the muscles of the legs and/or arms.
Spasticity is inconsistent, depending on many factors, including infections, temperature, stress, pain, position and time of the day. Severe spasticity may cause decreased range of motion in the affected limbs over time.
Spasticity is the result of an imbalance in the central nervous system, caused by a trauma or disease in the brain and/or spinal cord. This imbalance causes hyperactive muscle stretch reflexes, which result in involuntary contractions.
Some doctors believe that an increased sensitivity in the parts of the muscles that are responsible for contracting (tightening), relaxing and stretching the muscles contribute to spasticity.