Classification of phenotype characteristics in adult-onset spinal muscular atrophy

Degenerative lower motor neuron diseases (LMND) encompass a group of rare clinically and genetically heterogeneous disorders with the hallmark of anterior horn cell degeneration in the spinal cord and brainstem. In a recently proposed classification, LMND were subdivided according to the clinical disease pattern and time course. This study was performed to investigate the clinical practicability of the classification.

In 22 patients with adult LMND (mean disease duration, 24 years), the disease course and detailed clinical, electrophysiological, magnetic resonance imaging, laboratory, and genetic investigations were analyzed.

All patients could be assigned to the distinct disease subgroups, i.e. 11 patients to the slowly progressive generalized form (group 1), one to the distal form (group 2), 3 to the segmental distal form (group 3a), and seven to the segmental proximal form (group 3b).

The proposed classification was confirmed to be a practicable tool, and additional implications for the classification of LMND could be drawn from the data in our patient sample.