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Symptoms and clinical language

Primary lateral sclerosis

A related condition affecting only the upper motor neurons, with stiffness rather than muscle wasting.

What it means

Where ALS involves both relays of the movement pathway, PLS involves only the upper one. That produces stiffness and slowness without the muscle wasting and twitching seen in ALS. Diagnosis often takes time, because the two can look alike early on, and some people diagnosed with it are later found to have ALS/MND.

Why you might hear it

  • It may be mentioned while a diagnosis is still being worked out.
  • It appears in research listings alongside ALS/MND.

People who may help

Where Compass goes into this

About this explanation

These are plain explanations of words you may come across, not advice about your own situation. Where a word matters to a decision, the question pages go into it properly, and your own team is the place to take it.