Spasticity is a condition of increased, constant muscle tension that causes resistance to movement. The tension in the muscles is called muscle tone. It occurs because of a disruption in communication between the brain and the muscles.
Normally, muscles hold enough tension to resist gravity and perform activities, while also staying relaxed enough to be flexible and allow movement. The ideal balance of tension in each muscle varies from moment to moment, and the muscles and the brain are usually in constant communication about that balance.
To communicate, muscles send signals along sensory nerve fibers to the spinal cord. Muscles generally send the information that they will contract. The spinal cord relays those signals to the brain. The brain communicates back via motor nerve fibers, which control motion. The signals that the brain sends along the motor nerve fibers modulate how much the muscle contracts or relaxes.
In spasticity, signals from the brain do not pass through the motor nerve fibers normally to modulate the muscle’s tension. Without input from the motor nerve fiber to modify the contraction, the muscle simply contracts.
Spasticity causes stiff muscles, rigid joints, limited mobility, and pain. Depending on the muscles involved, spasticity may make it impossible for an individual to either bend or straighten his or her arms, legs, wrists, ankles, fingers, or other joints. Arms or legs may scissor, or cross; parts of the body may experience clonus, or repetitive jerky movements. Spasticity can affect speech, posture, gait (walking), and other activities of daily living. The constant muscle contractions often cause chronic spasms and pain.
Effects of spasticity can range from mildly troublesome to debilitating. However, several techniques and treatments can greatly improve the quality of life of individuals with the condition.
Causes and Risk Factors
Spasticity in children has many possible causes.
One common cause is cerebral palsy, a condition of brain damage that may occur before, during or shortly after birth. Cerebral palsy affects one to two out of every 1,000 children. The condition affects an area of the brain called the cerebral cortex, which controls movement.
Spinal cord injury, traumatic brain injury, spina bifida and myelomeningocele are other causes of spasticity in children. Both types of injury can interfere with communication between brain and muscles.
Tethered cord can also cause spasticity due to its effect on the spinal cord.
Rare metabolic disorders such as adrenoleukodystrophy, phenylketonuria (PKU) and Krabbe disease may lead to spasticity due to their effects on nerve fibers.
Tests and Diagnosis
Thorough physical and neurological testing from a multidisciplinary team will determine the cause and the extent of the spasticity. Physical and occupational therapists, child neurologists, physical medicine and rehabilitation doctors, neurosurgeons, orthopedic surgeons, nurses, and orthotists work together to determine which exact muscles are affected by spasticity and the most effective methods to treat them.
A variety of non-surgical and surgical treatments exist. These include physical and occupational therapy, medications, injection therapy (Botox), casting, and orthopedic surgical treatments. At the Spine Hospital at the Neurological Institute of New York, neurosurgical treatments include intrathecal baclofen pumps and selective dorsal rhizotomy.
Baclofen pumps are devices implanted in the abdomen that can deliver medicine directly to the fluid around the spinal cord, thereby achieving much higher doses of the medication at the spinal cord where it needs to act and much lower doses systemically to minimize side effects.
Selective dorsal rhizotomy is a surgical procedure in which sensory nerve roots are tested for abnormal activity through sophisticated neurophysiological monitoring and direct palpation of the muscles during the surgery, and the most spastic nerve roots are cut. This procedure is the most powerful method to reduce spasticity permanently and improve overall function. At the Spine Hospital, pediatric neurosurgeons perform this surgery with a minimally invasive approach. With this approach, the surgery is conducted through a small incision, only about 1.5 inches in length. Both the surgery itself and the recovery are faster than with a traditional, “open” surgical approach.