[The differential diagnosis of amyotrophic lateral sclerosis]

The diagnosis of amyotrophic lateral sclerosis (ALS) is mainly a clinical one. Nonetheless, electrophysiological studies must be performed early in order to confirm the diagnosis. The El Escorial criteria for the diagnosis of ALS, recently revisited in order to increase their sensitivity, have been widely accepted and help neurologists to categorize patients into various levels of certainty from clinical assessment. However, the variability in clinical findings early in the course of the disease and the lack of any biological diagnostic marker make absolute diagnosis difficult. In this review, I propose a strategy for establishing differential diagnoses when faced to a pure motor deficit at the first evaluation, or at the electrophysiological study or during follow up.