Ultrastructural change of synapses of Betz cells in patients with amyotrophic lateral sclerosis.

This report concerns an ultrastructural study of the synapses present on the surface of somata of normal-looking Betz cells in the fifth layer of motor cortex of seven patients with amyotrophic lateral sclerosis (ALS). Specimens from 12 age-matched, neurologically normal control individuals were included for comparison. Presynaptic terminals on the somata of normal-appearing Betz cells showed a wide range of changes including increased mitochondria, and the dark type of degenerative change of synapses such as dense conglomerates of dark mitochondria with dense cristae and densely aggregated presynaptic vesicles. These alterations were significantly more common in ALS patients than in controls, suggesting that a substantial synaptic change occurs in Betz cells even in the early stage of ALS.