Establishing Diagnostic and Differential Diagnostic Criteria for Amyotrophic Lateral Sclerosis.

Motor neuron disease (MND) represents a broad and heterogeneous group of disorders involving the upper or lower motor neurons, represented mainly by amyotrophic lateral sclerosis (ALS), primary lateral sclerosis (PLS), progressive muscular atrophy (PMA) and progressive bulbar palsy (PBP). Primary motor neuronopathies are characterized by progressive degenerative loss of anterior horn cell motoneurons (lower motor neurons) or loss of giant pyramidal Betz cells (upper motor neurons). Rare atypical variants of MND-ALS include flail arm syndrome (FA), flail leg syndrome (FL), facial-onset sensory and motor neuronopathy (FOSMN), finger extension weakness and downbeat nystagmus motor neuron disease (FEWDON-MND) and long-standing and juvenile MND-ALS. In this article, we present a review of diagnostic criteria and the differential diagnosis for MND, focusing on ALS.