Primary Lateral Sclerosis (PLS)

What is PLS?

PLS is a condition affecting the upper motor neurones. The degradation of upper motor neurones within the brain and spinal cord (which control your voluntary movement) causes disabling spasticity and weakness.

As muscles are not directly affected, there is no muscle shrinkage or fasciculations (sub-dermal muscle twitches), with this type of MND. PLS only affects the upper motor neurones, not the lower. PLS generally affects people above the age of fifty.

How is it diagnosed?

A lot of the tests which need to take place are in fact to exclude other conditions which could also be responsible for the symptoms. These conditions couls include multiple sclerosis, viruses, brain or spine tumours or spinal damage. ALS (Amyotrophic Lateral Sclerosis), which is the most common type of motor neurone disease, affecting both the upper and lower motor neurones, also needs to be excluded as a possibility.

What are the tests?

Tests performed include:

  • MRI scans to rule out any abnormalities in the brain or spinal cord
  • Nerve conduction tests (small electric shocks which are used to check the speed of nerve conduction to the muscles)
  • Electromyography (EMG)
  • Blood tests to check for other possible diseases

What are the symptoms?

PLS symptoms include: weakness in the lower limbs, loss of balance, stiffness in the limbs, clumsiness with hands, slurring your speech, emotionally inappropriate behaviour (for example laughing or crying without due cause), difficulty speaking or swallowing and occasionally bladder problems.

Life Expectancy

Life span with PLS could generally be normal, though it may be detrimental to life expectancy, depending on whether the disease remains as PLS, or progresses into ALS.

How will I be affected?

You will be more likely to fall over, as balance is impaired. Some people also experience some level of pain in the neck, back and legs. Things like washing, dressing, writing, and cooking, as well as other day to day tasks may be difficult, because of the reduction in your mobility. You could have speech problems may because the muscles in the throat and neck become more difficult to operate. This can also result in lessened control of the tongue, lip and palate, causing further loss of ability to speak clearly. Swallowing difficulties arising from the problems within the mouth and throat may result in issues with eating and drinking. There may potentially be a lack of emotional control to contend with.

Managing PLS

Managing PLS is mostly done by managing the individual symptoms as they manifest. This can include medication in order to alleviate muscle cramping and tightness and physical therapy and exercise in order to maintain the patient’s flexibility and range of motion. Equipment to assist with day to day activities and communication aids may also be used.


Light, low impact exercise such as walking or water aerobics can help strengthen muscles to help compensate for those which are weakened by the condition. Stretching exercises such as yoga or pilates could also lessen the severity of muscle cramps and help to maintain motion. The doctor may also prescribe medication to relieve your cramps and stiffness.


Speech may become impaired over time. There are many aids that could be useful to continue communication. Your doctor will discuss these with you to see what might be appropriate for you.


You may be dependent on others for the purposes of feeding. If feeding gets difficult and tiring because of the throat muscles being impaired, it may be the time to consider PEG feeding.

Remember at every stage to consult with your doctor to establish what is going on with your own health, what problems you have and how they can best be minimised or overcome.

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