Phrenic nerves of 11 patients with amyotrophic lateral sclerosis studied postmortem contained only 33% of the normal number of large myelinated fibers (9 controls; p < 0.001). In the phrenic nerves of these patients, there were 18% fewer large myelinated fibers in the distal segment than in the proximal segment (p < 0.025). The ratio of axonal circumference to myelin lamellae in large myelinated fibers in the distal segment was 34% greater than that in control fibers (p < 0.002). The proportion of acute axonal degeneration was the same at all levels (48.0 ± 13.7%). Sural nerves of 21 patients with amyotrophic lateral sclerosis had more acute axonal degeneration and 30% fewer myelinated fibers (p < 0.05) than controls; evidence of degeneration also extended to unmyelinated fibers. The amount of axonal transport of acetylcholinesterase in 9 sural nerves determined in vitro was reduced by 24% (p < 0.05) and the apparent transport rate was reduced by 44% (p < 0.01) compared with 4 controls. These findings show that in amyotrophic lateral sclerosis a small degree of dying-back change and of distal axonal atrophy is superimposed on the degradation of motor neuron cell bodies, and that the disease effects spread beyond the motor neurons.
ASJC Scopus subject areas
- Clinical Neurology