Electroencephalographic Assessment of Coma

Alpha coma evolving into spindle coma in a case of acute fulminant hepatic failure: What does it signify?

A 44-year-old male developed acute fulminant hepatic failure of unknown etiology and expired within four days. His serial electroencephalograms (EEGs) showed diffuse background slowing on day one, which evolved into "alpha coma" and later into "spindle coma" over the ensuing two days. Such EEG transition is hitherto undescribed in patients with hepatic encephalopathy and gives fresh insight into the etiopathogenesis of specific EEG patterns in diffuse encephalopathy.

Nonconvulsive status epilepticus and coma

Nonconvulsive status epilepticus (NCSE) in a comatose patient cannot be diagnosed without electroencephalography (EEG). In many advanced coma stages, the EEG exhibits continuous or periodic EEG abnormalities, but their causal role in coma remains unclear in many cases. To date there is no consensus on whether to treat NCSE in a comatose patient in order to improve the outcome or to retract from treatment, as these EEG patterns might reflect the end stages of a dying brain. On the basis of EEG, NCSE in comatose patients may be classified as generalized or lateralized. This review aims to summarize the ongoing debate of NCSE and coma and to critically reassess the available literature on coma with epileptiform EEG pattern and its prognostic and therapeutic implications. The authors suggest distinguishing NCSE proper and comatose NCSE, which includes coma with continuous lateralized discharges or generalized epileptiform discharges (coma-LED, coma-GED). Although NCSE proper is accompanied by clinical symptoms suggestive of status epilepticus and mild impairment of consciousness, such as in absence status or complex focal status epilepticus, coma-LED and coma-GED represent deep coma of various etiology without any clinical motor signs of status epilepticus but with characteristic epileptiform EEG pattern. Hence coma-LED and coma-GED can be diagnosed with EEG only. Subtle or stuporous status epilepticus and epilepsia partialis continua-like symptoms in severe acute central nervous system (CNS) disorders represent the borderland in this biologic continuum between NCSE proper and comatose NCSE (coma-LED/GED). This pragmatic differentiation could act as a starting point to solve terminologic and factual confusion.

Diagnostic and prognostic use of bispectral index in coma, vegetative state and related disorders

PRIMARY OBJECTIVE

This study investigates (1) the utility of the bispectral index (BIS) to distinguish levels of consciousness in severely brain damaged patients and, particularly, disentangle vegetative state (VS) from minimally conscious state (MCS), as compared to other EEG parameters; (2) the prognostic value of BIS with regards to recovery after 1 year.

RESEARCH DESIGN

Multi-centric prospective study.

METHOD AND PROCEDURES

Unsedated patients recovering from coma were followed until death or transferal. Automated electrophysiological and standardized behavioural assessments were carried out twice a week. EEG recordings were categorized according to level of consciousness (coma, VS, MCS and Exit MCS). Outcome was assessed at 1 year post-insult.

MAIN OUTCOMES AND RESULTS

One hundred and fifty-six EEG epochs obtained in 43 patients were included in the analyses. BIS showed a higher correlation with behavioural scales as compared to other EEG parameters. Moreover, BIS values differentiated levels of consciousness and distinguished VS from MCS while other EEG parameters did not. Finally, higher BIS values were found in patients who recovered at 1 year post-insult as compared to patients who did not recover.

CONCLUSION

EEG-BIS recording is an interesting additional method to help in the diagnosis as well as in the prognosis of severely brain injured patients recovering from coma.

Interobserver agreement in the interpretation of EEG patterns in critically ill adults

The significance of rhythmic and periodic EEG patterns in critically ill patients is unclear. A universal terminology is needed to facilitate study of these patterns, and consistent observer agreement should be demonstrated in its use. The authors evaluated inter- and intraobserver agreement using the standardized terminology (Hirsch et al., J Clin Neurophysiol 2005;22:128-135) recently proposed by the American Clinical Neurophysiology Society. Trained electroencephalographers viewed a series of 10-second EEG samples from critically ill adults (phase I), a set of >/=20-minute EEGs from the same patient cohort (phase II), and then reevaluated the first sample set (phase III). The readers used the proposed terminology to "score" each EEG. For each possible term, interobserver agreement (phases I and II) and intraobserver agreement (phase III) were calculated using pairwise kappa (kappa) values. Moderate agreement beyond chance was seen for the presence/absence of rhythmic or periodic patterns and for localization of these patterns. Agreement for other terms was slight to fair. Inter- and intraobserver agreement were consistently lower for optional terms than mandatory terms. Even when standardized terminology is used, the description of rhythmic and periodic EEG patterns varies significantly. Further refinement of the proposed terminology is required to improve inter- and intraobserver agreement.

Alpha coma pattern in a child

Alpha coma, an EEG pattern characterized by diffuse or widespread rhythmic activity in the alpha frequency band, is typically recorded in patients with profound coma and is frequently associated with severe neurological conditions. The most common etiologic factors of this pattern are hypoxic-ischemic encephalopathy, encephalitis, head trauma, metabolic disorders, and drug overdose. Reports of alpha coma pattern in children are relatively common. Clinical significance, both in children and adults, is variable, and highly dependent on etiology. The objective of this article is to report a clinical case of alpha coma pattern in a child with neuroblastoma. The EEG pattern was recorded during the evolution of treatment, secondary to complicating septic encephalopathy. The alpha coma pattern was replaced by a normal trace following a favorable outcome after sepsis resolution.

Mechanisms of neurologic failure in critical illness

Critical illness frequently is associated with neurologic failure that may involve the central and peripheral nervous systems. Central nervous system failure is associated with a spectrum of neurobehavioral changes including delirium, coma, and long-term cognitive dysfunction. Peripheral neurologic failure, or critical illness neuromuscular abnormalities, is suggested by diffuse arreflexic weakness and protracted respiratory insufficiency, and may also persist long after the acute hospitalization. While the burden of neurological disease complicating critical illness is considerable, preventive or therapeutic options are limited. This article provides an overview of research evaluating the relationship between critical illness and neurologic function, with a special emphasis on underlying mechanisms.