Primary Lateral Sclerosis

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Primary lateral sclerosis is a disease of the motor neurons that is both degenerative and progressive. This condition affects the body’s nerve cells that are responsible for controlling voluntary muscle movement. As time passes, the function of these motor neurons is lost. How the nerve cells are destroyed and how this condition occurs is not known. This condition seems to start after 50 years of age. It is very rare and incidence is unknown.


The adult form of this disease has no identifiable cause. Why or how it begins is unknown and it is not inherited in most cases.

The juvenile for does have an identifiable cause. An ALS2 gene mutation is responsible. Exactly how this gene mutation causes this disease is not completely understood, but it is know that this gene is necessary for giving instructions on creating the alsin protein. This protein is found heavily in motor neuron cells. When the instructions are altered, the alsin protein doesn’t function properly and becomes unstable, which results in normal muscle function impairment. Adults who develop this condition as adults do not seem to have an ALS2 gene mutation.


When the nerve cells are lost, muscles become hard to move and stiff. The issues typically begin in the legs and make their way up to the arms, trunk, and neck and facial muscles. Over a few years, this condition tends to slowly progress. The symptoms of this disease will slowly get worse at time passes. Symptoms may include:

  • Trouble walking, such as stumbling or tripping
  • Moving the arms may become difficult and make things like brushing the teeth or hair difficult
  • Swallowing and speaking may become difficult
  • The patient may have painful muscle spasms in the neck, back, or legs
  • Legs may become weak, stiff, and spastic
  • Hoarseness, slurred speech, drooling, and reduced speaking rate as weakening of the facial muscles occurs
  • In the later stages of this disease, breathing may become difficult


There is not just one test that can diagnose primary lateral sclerosis. The diagnostic process also involves ruling out other similar conditions. After a careful examination and discussing the patient’s medical history, the doctor will do a full neurological exam. Other tests may include:

Blood work may be done to look for other things that may cause muscle weakness and to rule out infections.

Sensory and motor nerve conduction studies are done to look for signs of damage to nerve cells. This test uses small amounts of electrical current to evaluate how well the patient’s nerves carry impulses throughout their body.

Cerebrospinal fluid analysis may be done to rule out the other possible causes of spasticity, such as multiple sclerosis. This test is done by inserting a needle into the spine in the lumbar region of the spine to obtain a sample of spinal fluid.

Magnetic resonance imaging may be done to get a good look at the patient’s spine and brain. This test may show signs of nerve cell degeneration. It may also help to rule out spinal cord compression, spinal cord tumors, structural abnormalities, and multiple sclerosis.

An electromyogram may be done to differentiate between ALS and PLS by measuring lower motor neuron involvement. This test is performed by inserting needle electrodes into different muscles, through the skin. Muscle electrical activity is evaluated when at rest and during contraction.


This condition cannot be cured, prevented, or reversed so treatment focuses on preserving function and reducing symptoms. There are medications to reduce muscle spasms. If oral medications are not effective, a medication pump may be surgically implanted so that medications to control spasticity can be delivered directly into the patient’s spinal fluid.

Speech therapy may be helpful for patients whose speech is affected. Physical therapy may help to maintain flexibility, strength, and range of motion. It can also help some patients prevent joint immobility. Assistive devices may help patients maintain some mobility.

Resources (2010). Primary Lateral Sclerosis. Retrieved on November 20, 2010 from

National Institute of Neurological Disorders and Stroke. (2010). NINDS Primary Lateral Sclerosis Information Page. Retrieved on November 20, 2010 from the National Institute of Neurological Disorders and Stroke: