Posthypoxic Myoclonus and Its Management

Abstract

Posthypoxic myoclonus (PHM) is a possible sequela of acute hypoxic events. An acute form and a chronic form (the latter also referred to as Lance-Adams syndrome, LAS) have been described. Acute PHM is usually associated with a poor prognosis. LAS, instead, is characterized by myoclonus presenting or persisting as patients regain consciousness. It can improve over time, and when additional neurological symptoms are present those are usually mild. Differentiating these two phenotypes based on clinical and neurophysiological assessments (such as electroencephalogram recordings and somatosensory evoked potentials) is not always straightforward, although very important because of the different prognostic implications. There are differences in therapeutic approaches for acute and chronic PHM because of the different nature of the myoclonus (cortical vs. subcortical or a combination of the two) and concurrent events. Multidrug approaches are usually required in both settings, mostly leveraging antiepileptic medications. In patients with persistent and debilitating LAS, multistep and even surgical approaches, such as deep brain stimulation, can be attempted to maximize functional recovery.KeywordsLance-Adams syndromeCortical myoclonusSubcortical myoclonusReticular reflex myoclonusMyoclonus status epilepticusMyoclonic statusNegative myoclonusStimulus-induced myoclonusBack-averageTime-locked potentialsSodium oxybateDeep brain stimulationHypoxic brain injury prognostication