The Interpretation of the EEG in Stupor and Coma

Abstract

This review discusses a variety of causes of stupor and coma and associated electroencephalographic (EEG) findings. These include metabolic disturbances such as hepatic or renal dysfunction, which are often characterized by slowing of background rhythms and triphasic waves. Hypoxia and drug intoxications can produce a number of abnormal EEG patterns such as burst suppression, alpha coma, and spindle coma. Structural lesions, either supra- or infratentorial, are reviewed. EEGs in the former may show focal disturbances such as delta and theta activity, epileptiform abnormalities, and attenuation of faster frequencies. In infratentorial lesions, the EEG may appear normal, particularly with a pontine lesion. Some patients may be encephalopathic because of ongoing epileptic activity with minimal or no motor movements. This entity, nonconvulsive status epilepticus (NCSE), is difficult to diagnose in obtunded/comatose patients, and an EEG is required to verify the diagnosis and to monitor treatment. Several EEG patterns and their interpretation in suspected cases of NCSE such as periodic lateralized epileptiform discharges (PLEDs), bilateral independent periodic lateralized epileptiform discharges (BIPLEDs), generalized periodic epileptiform discharges (GPEDs), and triphasic waves are reviewed. Other entities discussed include the locked-in syndrome, neocortical death, persistent vegetative state, brainstem death, and brain death.

Electroencephalogram signatures of loss and recovery of consciousness from propofol

“…We speculate that, as a result, sleep slow waves might show less pronounced phase-amplitude modulation than the propofol-induced slow oscillation (peak-max). EEG patterns similar to those described here during propofolinduced unconsciousness, including frontal alpha waves, lowfrequency oscillations, and burst-suppression, can be observed in different coma states (1,65). However, less is known about the spatiotemporal dynamics and mechanisms of these EEG patterns in coma, and further study will be required to make detailed comparisons with GA. More generally, systematic analyses comparing GA, sleep, coma, and other altered states of consciousness may yield important insights into the mechanisms underlying these phenomena.…”

Interpreting EEG alpha activity

“…If we assume that longer spindles of stable brain activity imply less information to process (as reflected by higher stability of the brain generator) and shorter segments imply a higher number of brain microstates, caused by an increased number of steps of information processing, it is possible to suggest that the intra-segment alpha amplitude variability could be indexing phase resetting activity (Oprisan et al, 2004). Indeed, intra-spindle segment amplitude variability decreases in coma or stupor (Brenner, 2005), but has been shown to increase during cognitive loading (Kaplan & Borisov, 2003) …”

Comments for Current Interpretation EEG Alpha Activity: A Review and Analysis

“…Probably, alpha-bursts are associated with a brain microstate change (such as sleep spindles), as demonstrated by its phasic intrusion in a desynchronized background of brain activity [68]. Important to know that intra-spindle amplitude variability decreases in coma or stupor [81], but increases during cognitive loading [75] and in relation to the ability for self-control in neuronfeedback training (18 -20 sessions) [56].…”