The electroencephalographic findings in acute intermittent porphyria

Propofol and sevoflurane induce distinct burst suppression patterns in rats

Burst suppression is an EEG pattern characterized by alternating periods of high-amplitude activity (bursts) and relatively low amplitude activity (suppressions). Burst suppression can arise from several different pathological conditions, as well as from general anesthesia. Here we review current algorithms that are used to quantify burst suppression, its various etiologies, and possible underlying mechanisms. We then review clinical applications of anesthetic-induced burst suppression. Finally, we report the results of our new study showing clear electrophysiological differences in burst suppression patterns induced by two common general anesthetics, sevoflurane and propofol. Our data suggest that the circuit mechanisms that generate burst suppression activity may differ among general anesthetics.

Rhythmic diffuse delta frequency activity presenting as an unusual EEG correlate of nonconvulsive status epilepticus: three case studies

We report three cases of nonconvulsive status epilepticus (NCSE) in which electroencephalograms (EEGs) were dominated by rhythmic or semirhythmic, high-voltage, diffuse, delta activity. These recordings initially contained little or no clear epileptiform activity. Two of these patients had prolonged episodes of NCSE, which were recorded with continuous long-term EEGs. These recordings revealed focal epileptiform discharges as well as persistent generalized epileptiform patterns. Rhythmic or semirhythmic, diffuse, delta activity with little or no clear epileptiform components has only rarely been reported with NCSE. Diffuse delta slowing is commonly seen in many toxic-metabolic encephalopathies, and this activity may occasionally appear rhythmic. EEG and clinical characteristics that may help distinguish these conditions are discussed.

The EEG in coma

The EEG allows insight into thalamocortical function in comatose patients when this is inaccessible clinically. A single EEG can help with broad diagnostic categorization whereas continuous or serial EEG provides monitoring for unstable and potentially treatable conditions and for monitoring the effects of therapy. The EEG plays a supplemental role in establishing the prognosis in disease states that are capable of causing neuronal death. The most prevalent and problematic of these conditions involves survivors of cardiac arrest who are initially in coma with intact brainstem reflexes. In such patients single EEGs are of 100% specificity for no possibility of recovery of consciousness only for essentially complete generalized suppression (<10 microV) after the first day of the arrest. Several other generalized patterns, including less marked suppression, burst-suppression, epileptiform activity, periodic complexes, and alpha-theta coma patterns, usually but not invariably indicate a poor outcome. Serial EEGs, continuous raw and automated "trending," testing of reactivity, and the inclusion of multiple variables hold promise for an improved role in the prognostic determination in these patients.