Spasticity

Spasticity is a condition described by stiff or rigid muscles and exaggerated deep tendon reflexes, that interferes with muscular activity, gait, movement, or speech. This means that if one tries to move the arm or leg, resistance increases as the speed of the movement is increased. In some cases, the rapid increase in resistance leads to a ‘catch’ as the limb is moved, with a subsequent release of the resistance once the limb stops moving.

What is spasticity?
What are the causes?
How is the diagnosis made?
What is the treatment?

What is spasticity?

What are the causes?

Spasticity is one symptom of the "upper motor neuron syndrome," a condition caused by damage to portions of the brain or spinal cord controlling movement. It generally results from damage to the motor area of the brain (the portion of the cerebral cortex that controls voluntary movement) and to any portion of the subcortical white matter (nerves travelling from brain down to spinal cord).

When control of the muscles from the central nervous system is affected, muscle feedback pathways from the spinal cord produce symptoms such as exaggerated deep tendon reflexes (the knee-jerk reflex), scissoring (crossing of the legs as the tips of scissors would close), repetitive jerky motions (clonus), unusual posturing, and carrying the shoulder, arm, wrist, and finger at an abnormal angle. Spasticity may also interfere with speech. Severe, long term spasticity may lead to contracture of muscles causing joints to be bent at a fixed position.

The common causes are:

Cerebral palsy
Brain damage caused by lack of oxygen, as can occur in near drowning or near suffocation
Brain trauma
Severe head injury
Spinal cord injury
Stroke
Some metabolic diseases
Neurodegenerative illness
Multiple sclerosis and other demyelinating diseases

How is the diagnosis made?

In order to examine a child with spasticity, the involved muscles must be stretched at varying speeds. For example, if the muscles of the upper leg are involved, then, during the examination, the knee is flexed and then extended at slow, intermediate, and fast speeds. Evaluating these stretches helps in determining if the resistance varies with velocity or if "catch" occurs as the velocity becomes fast enough and the spasticity has time to activate. Often there is also a "clasp-knife" release, in which there is a sudden reduction in resistance following the catch.

The medical history is obtained and a physical examination performed.

Medical history questions documenting spasticity in detail may include:

When was it first noticed?
How long has it lasted?
Is it always present?
How severe is it?
What muscles are affected?
What makes it better?
What makes it worse?
What other symptoms are also present?

In children with mild or moderate spasticity, the resistance to slow movements is not increased. Therefore, if the evaluator perceives a continuous "waxy" or "lead-pipe" feeling, this is more suggestive of dystonia or parkinsonian rigidity. Since spasticity is thought to be caused by a failure in communication between the brain and spinal cord, it is also important to check for other evidence of such failure.

In particular, the involved muscles may be weak, with primitive withdrawal reflexes. The mechanism in the body that produces spasticity is probably an increase in the stretch reflex; therefore, it is important to look for signs of increased stretch reflex or clonus (multiple jerks from a single tendon tap) throughout the body. The location of spasticity, weakness, and increased reflexes may be a clue to the location of the interruption of communication.

In spasticity due to brain injury, including cerebral palsy, it is helpful to determine the overall distribution of weakness in order to classify the syndrome appropriately as diplegia, hemiplegia, etc. As with other childhood movement disorders, spasticity may be only one of several symptoms that are simultaneously present. It is therefore important to examine for dystonia and rigidity contributing to limb stiffness, as well as other possible disorders.

What is the treatment?

There is much research investigating possible repair of damaged cells in the brain or spinal cord; however, there is no effective treatment that reverses the injury.

Spasticity may often be helped by physical therapy. Daily routines of exercise including muscle stretching to prevent joint contractures will help reduce the severity of symptoms of severe spasticity. Physical therapy can be taught to parents who may then administer the care at home. Stretching exercises, muscle group strengthening exercises, and repetitive motion exercises (for improvement of accuracy and performance at given tasks). Occasionally, surgery is required for tendon release or severing of the nerve-muscle pathway.

Medication for spasticity can be taken orally. These medications include Baclofen, Tizanidine and Benzodiazepines. Rarely, a pump can be inserted into the spinal fluid and medication can be administered directly into the nervous system.

Botulinum toxin is an effective treatment for children with spasticity as it causes a temporary weakening of spastic muscles. It is also possible that the toxin decreases the signals coming from the muscle stretch receptors, thereby directly reducing the signals that result in spasticity. Botulinum toxin is most effective when only a small number of muscles are involved; injections usually need to be repeated every 3 to 6 months.

Alternatives to botulinum toxin include injections of phenol or ethanol onto the nerves supplying the muscles. Larger and more powerful muscles are more often the target for these treatments. These treatments are also temporary, and carry a risk for pain in some nerves.

Any treatment for spasticity needs to take into account that the spasticity itself is only part of the problem. Because the connection from the brain to the spinal cord is damaged, the muscles are also weak in the sense that the one has reduced voluntary control.