Primary Lateral Sclerosis

Overview

Primary lateral sclerosis (PLS) is a rare neuromuscular disorder characterized by weakness in the muscles controlling the arms, legs, and tongue due to the degeneration of nerve cells. It can develop at any age but is more common between 40 and 60, especially in men. PLS has no known cure.

These nerve cells, called upper motor neurons, usually send messages from the brain to the muscles through the spinal cord, allowing voluntary muscles like those in the legs to move when needed. However, in PLS, the breakdown of these upper motor neurons leads to a lack of proper messages reaching the muscles, resulting in difficulties with movement over time.

PLS usually starts with balance issues and clumsiness, then progresses to difficulties with hands, arms, chewing, swallowing, and speaking. It can sometimes begin in childhood, called juvenile PLS, caused by a gene change inherited from both parents.

PLS is often confused with amyotrophic lateral sclerosis (ALS), but it progresses more slowly and is typically not fatal. While there is currently no cure for PLS, treatment aims to alleviate symptoms and improve quality of life.

Symptoms

Primary lateral sclerosis (PLS) manifests uniquely in each individual, with symptoms varying from person to person. Typically, it emerges gradually, often commencing in the legs before gradually spreading along the spinal cord, resulting in progressive weakness.

Initial symptoms may include:

• Spasticity, or muscle stiffness, spasm, and weakness in the legs
• Difficulty walking
• Difficulty maintaining balance, stumble often or becomes clumsy
• Decrease speed of motion

As the condition advances, additional symptoms may emerge, such as:

• Stiffness and weakness extending to the fingers, hands, and arms
• Bladder control issues
• Drooling, slow, slurred speech, and a scratchy voice
• Having difficulty swallowing and chewing
• Mood swings that are frequent, quick, and intense
• Lower back or neck pain

Although possible, PLS rarely start with hand or tongue weakness.

If any of the signs and symptoms are experienced or observed, consult a healthcare provider for proper diagnosis and treatment. Specifically, if one experiences ongoing stiffness or weakness in the legs or arms, difficulty swallowing or speaking, or if the child exhibits muscle spasms or increased balance issues, it is essential to schedule an appointment with a healthcare provider promptly.

Causes

Primary lateral sclerosis (PLS) is defined by the progressive degeneration of the brain’s motor nerve cells responsible for controlling movement.

Most cases of primary lateral sclerosis has no known cause.

• Adult-onset primary lateral sclerosis: This condition is typically not inherited. The reason behind its onset remains unclear.
• Juvenile primary lateral sclerosis: PLS in children is a hereditary autosomal recessive condition. This implies that for a gene to be passed on to a kid, both parents must be carriers. Mutations in the ALS2 gene are the cause of juvenile PLS.

The ALS2 gene provides instructions for making a protein known as alsin, which is found in motor neuron cells. In individuals with juvenile primary lateral sclerosis, alterations in these instructions result in unstable alsin protein that does not function correctly. This instability affects muscle function. However, experts are uncertain on how this particular gene leads to PLS.

Risk factors

Primary lateral sclerosis can occur in individuals of any age, although the average age of diagnosis is around 50 years old, with cases reported in both younger and older individuals, including children. It is also observed to be more prevalent in males. Additionally, there are no known environmental factors that have been definitively linked to the development of PLS.