Myoclonus Status and Prognostication of Postresuscitation Coma: The Bigger Picture

Prognostication in comatose survivors after out-ofhospital cardiac arrest is a flawed but necessary task that typically falls to the neurologist. The algorithms introduced by Levy and Plum in the 1970s—which have served generations of neurologists—as well as the American Academy of Neurology Practice parameter recognize that prognostication can only provide percentages of patients who fall into broad outcome categories, with many assigned to an unsatisfactory “indeterminate outcome” group. A small subset of patients, however, may display clinical and laboratory abnormalities, including neuroimaging and neurophysiology, that indicate a very low probability of awakening and even less likelihood of successful neurorehabilitation. Multiple tests, when taken together, yield a more informed judgment. In clinical practice, this “big picture” determines decisions on the level of care. Reliable analysis must include an unconfounded expert neurologic examination, detailed cardiac assessment, evaluation of other serious organ damage, and consideration of the patient’s prior functionality and advance directives. After much thought about giving prognostic information and decades of practice, we strongly believe this determination is still the territory of neurology. Persistent coma after acute circulatory standstill and successful return of circulation has been broadly and correctly considered an ominous situation. Awakening, when it occurs, is usually quick and sustained, although some of those patients have had focal injuries to the brain (eg, postarrest amnesia). Failure to awaken implies a more widespread structural injury to susceptible areas such as the cortical mantle, diencephalon, striatum, and globus pallidus. Motor response has been identified as a prime indicator of anoxic–ischemic injury. In a large prospective study of 210 carefully examined patients, Levy and colleagues identified a combination of factors to be considered when prognosticating after cardiopulmonary resuscitation including: (1) time interval from the arrest, (2) level of motor response, and (3) retained brainstem reflexes and roving eye movements. Their results culminated in charts carried in the pockets of many neurologists consulting in intensive care units. A later study by Greer and associates in 200 patients in the post-therapeutic hypothermia era and found largely similar results, except for the role of spontaneous eye movements. For many years, myoclonus status in the immediate postischemic period—sometimes erroneously called “myoclonic status epilepticus,” but not due to status epilepticus—has been recognized as an important indicator of severe anoxic–ischemic brain injury. This should be distinguished from myoclonus of the Lance–Adams variety that develops as a late feature during recovery in an awake patient. One of most prominent electroencephalographers, the late Ernst Niedermeyer, noted touch-sensitive myoclonus in 1977 and declared that “the prognosis of this state is extremely grave and most patients succumb within hours or days, while others may gradually slip into a chronic post-anoxic state. ” The significance of postischemic myoclonus status for poor outcome in comatose patients was more extensively examined in a study defining the condition as multifocal myoclonus preceded by electrographic discharge and lasting >30 minutes. Further studies found strong correlations of postischemic myoclonus status with the presence of a burstsuppression pattern on electroencephalography (EEG), cerebral edema on computed tomography, and extensive cortical and spinal cord injury at autopsy. Other studies selected on the basis of methodological quality led the American Academy of Neurology to conclude that the outcome of myoclonus status was poor, with a false-positive ratio of 0, but with a confidence level of 0 to 8.8%. The study by Elmer et al published in this issue of Annals of Neurology confirms that comatose survivors with postischemic myoclonus status have a very poor outcome (90% mortality). However, it provides important new insights into the role of continuous EEG monitoring in determining outcome and refines our understanding of the neurological prognosis after cardiac resuscitation. Elmer et al classified EEG recordings from 69 patients with myoclonus into 4 patterns after review by an epileptologist and a neurointensivist with expertise in anoxic brain injury. Pattern 1 consisted of burst-suppression, high-amplitude polyspikes, and pattern 2 involved continuous background and narrow, vertex spike-wave discharges. Patterns 1 and 2 were closely time-locked with myoclonic jerks. Pattern 3 showed myoclonus but no epileptiform discharges associated with myoclonic jerks, and pattern 4 consisted of the remaining subjects with more variable epileptiform patterns. The only survivors came from the group with pattern 2 (4 of 8 patients). The supplemental data on the survivors indicated awakening with 2 of 4 following commands but no