What is it?

Primary lateral sclerosis (PLS) is a type of motor neuron disease that causes nerves within the brain to slowly break down. This makes the nerves unable to activate the motor neurons in the spinal cord, which control muscles. PLS causes weakness in the voluntary muscles, such as those used to control the legs, arms and tongue. This condition can develop at any age, but it usually occurs between ages 40 and 60.

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Signs & symptoms

Signs and symptoms of primary lateral sclerosis (PLS) usually take years to progress. They include:
- Stiffness, weakness and muscle spasms (spasticity) in the legs, often starting in one leg
- Tripping, difficulty with balance and clumsiness as the leg muscles weaken
- Weakness and stiffness progressing to the trunk, then the arms, hands, tongue and jaw
- Hoarseness, as well as slowed, slurred speech and drooling as the facial muscles weaken
- Difficulties with swallowing and occasionally breathing late in the disease

Less commonly, PLS begins in the tongue or hands and then progresses down the spinal cord to the legs.


There is no single test that confirms a diagnosis of primary lateral sclerosis (PLS). In fact, because the disease can mimic signs and symptoms of other neurological diseases such as multiple sclerosis there is a need to perform several tests to rule out other diseases. After taking a careful record of medical history and family history and performing a neurological examination, a few tests may need to perform:
- Bloodwork: Blood tests check for infections or other possible causes of muscle weakness.
- MRI: An MRI or other imaging tests of the brain or spine might reveal signs of nerve cell degeneration.
- Electromyogram (EMG): The test evaluates the electrical activity of the muscles when they contract and when they're at rest. This test can measure the involvement of lower motor neurons, which can help to differentiate between PLS and ALS.
- Nerve conduction studies: These tests use a low amount of electrical current to measure the nerves' ability to send impulses to muscles in different areas of the body.
- Spinal tap (lumbar puncture): A spinal tap can help rule out multiple sclerosis, infections and other conditions.


There are no treatments to prevent, stop or reverse PLS. Treatment, which focus on relieving symptoms and preserving function, include:
- Medication: Such as baclofen, tizanidine (Zanaflex) or clonazepam (Klonopin) to relieve muscle spasms (spasticity). These medications are taken by mouth. If there is depression, there is a need for antidepressants. Amitriptyline and other drugs also can help drooling problems.
- Physical therapy: Stretching and strengthening exercises can help maintain muscle strength, flexibility and range of motion, and prevent joint immobility. Heating pads can help relieve muscle pain.
- Speech therapy: If facial muscles are affected by PLS, speech therapy might help.
- Assistive devices

☝️ This is not a substitute for professional medical advice. Please consult with your physician before making any medical decision.

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