Reticular reflex myoclonus: a physiological type of human post-hypoxic myoclonus.

Abstract

SUMMARY A patient with post-hypoxic myoclonus, sensitive to therapy with 5-hydroxytryptophan and clonazepam, was subjected to detailed electrophysiological investigation. Brief generalised jerks followed the critical stimulus of muscle stretch. The electroencephalogram showed generalised spikes that were associated with, but not time locked to, the myoclonus. The cranial nerve nuclei were activated upward. Analysis of the findings suggests that the mechanism of the myoclonus is hyperactivity of a reflex mediated in the reticular formation of the medulla oblongata.

The interrelation between clinical presentation and neurophysiology of posthypoxic myoclonus

“…The general hypothesis is that damage to the brainstem is worse in terms of prognosis compared to cortical lesions in PAE 1, 7. Generalized myoclonus has been associated with a subcortical origin,7, 8, 9, 10, 11 however in this study we showed that generalized PHM can be of cortical origin as well. Interestingly, Gentsch and colleagues (2015) found that the total amount of brain damage predicts outcome in PAE 36.…”

“…However, meanwhile, via the corpus callosum the contralateral motor cortex is activated as well (interhemispheric excitation spread), finally effectively producing a bilateral generalized jerk 33, 34, 35. Certainly, generalized PHM can arise from the brainstem 8. However, it is not clear if in every case damage to the brainstem is causative for its manifestation.…”

“…It is thought that the CM or SM represents the localization of anoxic brain decay in PHM patients 8, 33, 34, 35. The general hypothesis is that damage to the brainstem is worse in terms of prognosis compared to cortical lesions in PAE 1, 7.…”

“…Generalized PHM is associated with a subcortical origin. In this type of PHM the jerks are generalized and synchronous with predominant involvement of the proximal musculature 7, 8, 9, 10, 11. In contrast, focal PHM is associated with a primary cortical origin.…”

Myoclonus after Cardiac Arrest: Where Do We Go from Here?

“…One particular examination finding of prognostic importance is early posthypoxic myoclonus (PHM). Early PHM is defined clinically by focal, multifocal, or generalized myoclonic movements of the face, trunk, extremities, and sternocleidomastoid and trapezius muscles that begin within 72 hours of CRA (3)(4)(5)(6)(7)(8). Early PHM arises due to brain injury and subsequent increased neuronal hyperactivity (3,5,6).…”