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Content is anchored to trusted sources where available, but Compass has not yet been clinically reviewed. It provides general information rather than medical advice.

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El Escorial criteria

An older set of rules for classifying how certain an ALS diagnosis is, written mainly for research.

What it means

Named after the Spanish town where they were agreed. They sort a diagnosis into levels such as possible, probable and definite, based on how many regions of the body show changes. They were designed to make research groups comparable rather than to guide care, and a clinician may be confident where the criteria still say possible.

Why you might hear it

  • Trial eligibility is often written in these terms.
  • The words can read as doubt when they are describing a research category.

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.