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Abstract
Amyotrophic lateral sclerosis (ALS) shows peculiar abnormalities of the autonomic nervous system, including sympathetic hyperactivity, which might result in sudden death. In general, the sympathetic hyperactivity could be caused by disruption of vagal inhibition. Our objective was to evaluate the vagus nerve morphometrically in autopsy cases of ALS with sympathetic hyperactivity and circulatory collapse (CC). We investigated 10 autopsied ALS patients, six of whom had exhibited autonomic storms or CC. We also examined 10 patients without ALS as controls, and one patient with Guillain-Barré syndrome (GBS) who died from CC, for comparison. After obtaining the visceral branch of the left vagus nerve at necropsy, we analyzed the density of the myelinated and unmyelinated fibers, and the fiber diameter distribution for each fiber. Results showed that the densities of both myelinated and unmyelinated fibers in ALS patients with or without CC were not significantly different from those in control patients. In contrast, the GBS patient showed marked reduction in the whole myelinated and large unmyelinated fiber density. In conclusion, the autonomic storms or CC due to sympathetic hyperactivity in ALS could not be ascribed to the deafferentation of the baroreflex, and more central neural pathophysiology should be investigated.
Acknowledgements
This work was supported in part by a grant-in-aid for Scientific Research on Pathomechanisms of ALS from the Tokyo Metropolitan Organization for Medical Research, and in part by a grant-in-aid from the Research Committee of CNS Degenerative Disease, the Ministry of Health, Labor and Welfare of Japan.
Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.