Fig. 2.

Classification of ALS motor phenotypes. Onset region (O): Phenotypes of onset differentiate the site of first symptoms including the bulbar region, arm, trunk and leg; phenotypes of propagation (P) differentiate the earlier (within 12 months), later (after 12 months) or unclassifiable (monitoring of 12 months not completed) propagation of motor neuron dysfunction from the region of onset to another, vertically distant body region; phenotypes of motor neuron dysfunction (M) differentiate the degree of clinical upper (UMN) and lower motor neuron (LMN) dysfunction