Freund, Brin E

Purpose: Electroencephalogram is used for prognostication and diagnosis in critically ill patients and is vital in developing clinical management algorithms. Unique waveforms on EEG may distinguish neurological disorders and define a potential for seizures. To better characterize zeta waves, we sought to define their electroclinical spectrum. Methods: We performed a systematic review using MEDLINE, Embase, Cochrane Central Register of Controlled Trials and Cochrane Database of Systematic Review [through Ovid], Scopus, Science Citation Index Expanded and Emerging Sources Citation Index [through the Web of Science], and Epistemonikos. Grey literature resources were searched. Results: Five hundred thirty-seven articles were identified. After excluding duplicates and reviewing titles, abstracts, and bodies and bibliographies of articles, four studies reported 64 cases describing data from patients with zeta waves, with a prevalence of 3 to 4%. Various and often incomplete clinical, neuroimaging, and EEG data were available. 57 patients (89.1%) had a focal cerebral lesion concordant with the location of zeta waves on EEG. 26 patients (40.6%) had clinical seizures, all but one being focal onset. Thirteen patients (20%) had epileptiform activity on EEG. Typically, zeta waves were located in the frontal head regions, often with generalized, frontal, predominant, rhythmic delta activity and associated with focal EEG suppression. Conclusions: Zeta waves frequently represent an underlying focal structural lesion. Their presence suggests a heightened risk for seizures. The small number of retrospective cases series in the literature reporting zeta waves might be an underrepresentation. We suggest a need for prospective studies of cEEG in critically ill patients to determine their clinical significance.

AbstractTemporal lobe epilepsy is the most common form of focal epilepsy and is frequently resistant to antiseizure medication. Non‐invasive biomarkers are crucial when resective epilepsy surgery is considered in order to guide diagnostic work‐up and management. Interictal epileptiform discharges, when concordant with ictal EEG recording and a focal abnormality on functional imaging or anatomic MRI in patients with temporal lobe epilepsy, portend a favorable outcome with resective or ablative surgery. An interictal nonepileptiform feature on EEG believed to have the same localizing potential as epileptiform discharges is temporal intermittent rhythmic delta activity (TIRDA). The precise localization of TIRDA has been a subject of debate, but has been associated with seizures that arise from the temporal region. We report a 64‐year‐old female who underwent unsuccessful right anterior temporal lobectomy for drug‐resistant focal epilepsy, suspected to originate from the right temporal lobe. Subsequent video‐EEG monitoring revealed right, greater than left, TIRDA and interictal epileptiform discharges arising from the temporal regions bilaterally, despite a generous temporal lobectomy demonstrated by brain MRI. Further, using EEG source localization, we identified TIRDA using scalp EEG in sensor space, localized to the ipsilateral orbitofrontal region. We discuss the proposed localization of TIRDA in this case and address the importance of characterizing TIRDA in the presurgical evaluation of patients with epilepsy.

Summary: Prognostication following cardiorespiratory arrest relies on the neurological examination, which is supported by neuroimaging and neurophysiological testing. Acute posthypoxic myoclonus (PHM) is a clinical entity that has prognostic significance and historically has been considered an indicator of poor outcome, but this is not invariably the case. “Malignant” and more “benign” forms of acute PHM have been described and differentiating them is key in understanding their meaning in prognosis. Neurophysiological tests, electroencephalogram in particular, and clinical phenotyping are crucial in defining subtypes of acute PHM. This review describes the neurophysiological and phenotypic markers of malignant and benign forms of acute PHM, a clinical approach to evaluating acute PHM following cardiorespiratory arrest in determining prognosis, and gaps in our understanding of acute PHM that require further study.