Primary Lateral Sclerosis (PLS)

What is Primary Lateral Sclerosis?

Primary Lateral Sclerosisis also called PLS and central motor neuron disease of voluntary muscles. The cause of PLS is unknown but symptoms usually begin when the patient is between 40 to 60 years old. Patients are usually men. Just why men are affected more than women is still unknown.

Doctors are not quick to diagnose PLS. The National Institute of Neurological Diseases and Stroke note that doctors may take as long as 4 years in order to diagnose a PLS patient. This long time to reach a diagnosis is for two reasons:

The first is that symptoms come on so gradually that other conditions may be suspected.

The second is that the first symptoms are similar to other conditions, including other kinds of neurological diseases.

What are the Symptoms of Primary Lateral Sclerosis?

The good news is that PLS is mostly painless physically. Coordination is gradually lost in the body. The legs are usually the first affected. They become weak and stiff so walking or standing is difficult. For some patients, the tongue may be first affected. For others it is the hands. Wherever it starts, moving the affected body part is difficult. As the disease slowly progresses, other body parts are affected.

In the worse cases, the face, tongue, hands and legs are difficult to move or coordinate. They may jerk about spastically. The patients may no longer be able to talk, suffer urine incontinence. The worst symptom is the inability to swallow and the person loses the ability to eat. Liquid food is given via a tube directly to the stomach.

Primary Lateral Sclerosis (PLS) Causes

PLS is caused by the degeneration of nerve cells in the brain which control movement. When the disease appears in adults, it isn’t known why this process occurs. People aged 50 and over are most at risk of the condition, but experts have not yet been able to determine why.

When PLS occurs in children, it appears that a mutation of a gene called ALS2 is to blame. This gene aids in the production of a alsin, a type of protein which is found in motor neuron cells. In those with the mutation, it appears that the alsin protein becomes unstable and doesn’t work as normal, which affects the function of motor neuron cells.

PLS in juveniles is an autosomal recessive disease, which means that both parents must carry the relevant gene mutation. However, the parents don’t necessarily have the disease themselves, which makes it tricky to predict who will develop juvenile PLS.

How is Primary Lateral Sclerosis Treated?

There is no cure for PLS. However, unlike many other types of neuromuscular disease, PLS is not fatal because it does not interfere with breathing. Most patients go on to live out their full life span. Some even retain their ability to walk without even a cane to support them. Others are able to live by themselves without the need to hire a live-in nurse.

Individual symptoms are treated depending on the needs of each patient. Speech therapy helps some retain the ability to communicate. Wheelchairs, rollators, braces and canes help others to move about. Spastic motions may be treated with a type of medications called muscle relaxants.

It is normal for a PLS patient to become depressed before or after diagnosis. Anti-depressants are often prescribed to help the patient cope with the emotional impact of PLS.

Primary Lateral Sclerosis (PLS) Prevention

Since the causes of adult PLS in adults is unknown, there is no known way to prevent the disease. Even in children where the cause is known to be genetic, scientists have been unable to find a way to prevent the disease in those with the relevant mutated gene.

PLS is a progressive disease, so while it cannot be completely prevented, it may be possible to slow down the progression of weakness in muscle movement.

Physical therapy may help to maintain mobility in the joints and retain muscle strength in both children and adults. For those who experience weakness in the facial muscles, speech therapy may help to slow progression and prevent the patient from losing their ability to communicate. Medications may also be prescribed to prevent pain and spasticity.

Last Reviewed:
October 09, 2016
Last Updated:
January 11, 2018