Primary Lateral Sclerosis

What is Primary Lateral Sclerosis?

Also known as PLS, primary lateral sclerosis is a form of motor neurone disease that causes the muscle nerve cells to deteriorate, contributing to muscle weakness and restricted movement. Sometimes, PLS is mistaken for ALS (amyotrophic lateral sclerosis). However, this form of motor neurone disease progresses more rapidly and is often fatal.

What are the symptoms of PLS?

The symptoms of PLS usually progress over a protracted period of time and include:

• stiffness in the lower limbs
• lack of muscle strength
• weakness in the upper limbs and chest (the legs are usually affected first)
• slurred speech and hoarseness
• weakness in the facial muscles, which results in dribbling
• speaking slowly

What causes PLS?

Primary lateral sclerosis is caused by the gradual deterioration of the nerve cells in the brain that are responsible for movement. This causes symptoms linked to weak muscles and a lack of muscle control.

In most cases affecting adults, the cause of PLS is unknown. In cases affecting children, PLS is thought to be linked to genetic defects that affect the ALS2 gene. It is not fully understood how the defective gene causes symptoms. However, it is known that the ALS2 gene carries instructions to make alsin, a protein found in the motor neuron cells. If these instructions cannot be carried out, this affects the production of alsin and this leads to impaired muscle function. PLS in children is inherited from their parents. The condition is recessive, which means that a child must inherit the defective gene from both parents to develop the disorder.

What are the effects of PLS?

PLS is a progressive disorder and although symptoms can take up to 20 years to advance, PLS can take its toll on day to day life and make even the most mundane and simple actions more difficult. Some people are able to maintain a degree of independence for a long period of time, while others will be reliant on mobility aids and help from family or carers after just a short period of time.

PLS in adults does not usually affect life expectancy significantly, but it may have serious implications for quality of life.

Diagnosing PLS

There is no test to confirm a diagnosis of PLS, however a series of tests combined with assessment of symptoms can help doctors to reach a diagnosis. A doctor will usually start by looking at family and medical history and then assess symptoms. They will then order tests, including blood tests and imaging scans (such as CT and MRI scans) to determine a diagnosis. A test called EMG (electromyogram) may also be recommended. During this test, electrodes will be instated into the muscles through the skin. The test helps to analyse activity in the muscles while you rest and while you are active. A nerve conduction test, which monitors the transmission of nerve signals, may also be used. If symptoms are similar to multiple sclerosis, a lumbar puncture can be conducted. The results of the tests can be used to confirm a diagnosis and differentiate between PLS and other similar conditions, such as ALS.

Treating PLS

There is currently no cure for PLS and no means of slowing down the progression of the disorder. However, there are treatments and therapies that help to ease and prevent symptoms and improve quality of life.

The most commonly used treatments include:

• Medication: medicines may be prescribed to prevent muscle spasms. If medication is ineffective, a tap may be implanted to take medicine straight to the spinal fluid. Medication may also be recommended if you are showing signs of depression.
• Physiotherapy: physiotherapy can help to strengthen the muscles, reduce stiffness and increase the range of movement.
• Heat pads: These can be useful for easing pain.
• Speech and language therapy: This can help with speech problems associated with loss of strength and control in the facial muscles.
• Occupational therapy: Occupational therapy can help to increase independence and reduce the risk of accidents and injuries.