Abstracts

Rationale: Electrographic seizures are commonly considered when evaluating a patient with altered mental status. Without access to EEG data during off hours, diagnosis and treatment are often delayed for several hours to days, when an EEG technologist becomes available. An abbreviated, below-the-hairline EEG (BTH-EEG) using only 8 electrocardiogram electrodes has been shown to be useful in detecting interictal epileptiform abnormalities (Neurology 1988;38:146-149), but its usefulness in detecting electrographic seizures has been questioned (Epilepsia 2007;48(5):959-965). Methods: We reviewed all BTH-EEGs successfully performed and saved by neurology residents at Brigham and Women’s Hospital during night and weekend hours from 1/07 to 5/08. We analyzed demographic and clinical data in relation to whether or not an ictal pattern was identified, and these results were compared to the formal EEG subsequently obtained, usually the following day. Results: 37 studies were identified, ranging in duration from 2 min-18 hrs. Median age was 53 (range 25-81yrs); 20 were female. 7 of 37 BTH-EEGs showed at least one electrographic seizure, of which 4 also showed periodic discharges, all lateralized; an additional 7 had periodic discharges (2 bilateral, on a suppressed background); 1 patient had burst-suppression without discharges; the remainder had slowing, with variable asymmetries and proportions of theta and delta. No isolated interictal epileptiform discharges were observed. Follow-up formal EEGs showed electrographic seizures in 5 of 37 patients (including 3 of the 7 with ictal BTH-EEG and follow-up studies, and 2 whose BTH-EEGs showed periodic lateralized discharges). Periodic patterns were seen on follow-up studies of all who had them on BTH-EEG. Of the 7 patients with ictal BTH-EEGs, 4 had a history of previous seizures, and 4 had clinical seizure activity beyond the change of mental status (2 did not, and in 1 case this information was unknown). Neurology residents mentioned results of the BTH-EEG in 22 of 37 inpatient notes. All 7 with ictal BTH-EEGs survived to discharge, vs. 21 of the remaining 30. Conclusions: In selected cases, BTH-EEG can be useful in detecting subclinical seizures and/or other epileptiform patterns (e.g., periodic discharges) potentially affecting treatment. House officers can successfully perform and interpret these studies, and may use their findings in making treatment decisions. Though its sensitivity is imperfect, it is a fast, non-invasive, inexpensive tool that may save valuable time, especially when no other viable option is immediately available.