Acute posthypoxic myoclonus after cardiopulmonary resuscitation

Abstract

BackgroundAcute posthypoxic myoclonus (PHM) can occur in patients admitted after cardiopulmonary resuscitation (CPR) and is considered to have a poor prognosis. The origin can be cortical and/or subcortical and this might be an important determinant for treatment options and prognosis. The aim of the study was to investigate whether acute PHM originates from cortical or subcortical structures, using somatosensory evoked potential (SEP) and electroencephalogram (EEG).MethodsPatients with acute PHM (focal myoclonus or status myoclonus) within 72 hours after CPR were retrospectively selected from a multicenter cohort study. All patients were treated with hypothermia. Criteria for cortical origin of the myoclonus were: giant SEP potentials; or epileptic activity, status epilepticus, or generalized periodic discharges on the EEG (no back-averaging was used). Good outcome was defined as good recovery or moderate disability after 6 months.ResultsAcute PHM was reported in 79/391 patients (20%). SEPs were available in 51/79 patients and in 27 of them (53%) N20 potentials were present. Giant potentials were seen in 3 patients. EEGs were available in 36/79 patients with 23/36 (64%) patients fulfilling criteria for a cortical origin. Nine patients (12%) had a good outcome. A broad variety of drugs was used for treatment.ConclusionsThe results of this study show that acute PHM originates from subcortical, as well as cortical structures. Outcome of patients admitted after CPR who develop acute PHM in this cohort was better than previously reported in literature. The broad variety of drugs used for treatment shows the existing uncertainty about optimal treatment.

The interrelation between clinical presentation and neurophysiology of posthypoxic myoclonus

“…Moreover, in this cohort CM was more likely present in patients with generalized PHM than in focal PHM. This result is in line with earlier studies who demonstrated that generalized PHM can arise from the cortex 5, 6, 33. These findings suggest that the clinical model of typical CM and SM phenomenology that physicians encounter in noncomatose myoclonus patients at the outpatient clinic does not apply for PHM in the first few days after resuscitation 10, 11.…”

“…This finding suggests that patients with a multiple lesioned cortex (and CM) could have a worse outcome compared to patients with a singular, small brainstem lesion (and SM). In addition, studies that correlated the generalized and focal PHM phenotype to outcome found that the severity of myoclonus, and not per se the presence or absence of brainstem damage, was related to poor outcome 1, 5, 6. Yet in contrast, another finding of this study was that in patients presenting PHM within 24 h after CPR, significantly less CM occurred (Table 3).…”

“…The incidence of posthypoxic myoclonus (PHM) in resuscitated patients with postanoxic encephalopathy (PAE) is 19%, and only 9–14% of these patients recover with mild to no cognitive deficits 4, 5, 6…”

“…The survival of comatose patients with generalized PHM admitted at an intensive care unit (ICU) is reported to be poor (±3%) in comparison with focal PHM patients (±17%) 4, 5. Generalized PHM is associated with a subcortical origin.…”

The International Liaison Committee on Resuscitation (ILCOR) process for developing guidelines

“…The current hot topic in resuscitation is prog nostication. This field is moving rapidly, largely because of the accumulating evi dence that therapeutic hypothermia modi fies the recovery process in the comatose post cardiac arrest patient-we have un doubtedly been making withdrawal deci sions far too early in these patients [30,31]. The Swedish Resuscitation Council has al ready published updated guidelines on neurological prognostication after cardiac arrest [32] and I expect that other organi sations will publish guidance over the next few months.…”