Abstracts

Rationale: Inpatient video EEG monitoring is an important tool in spell classification and is currently the gold standard. The diagnostic yield of an Epilepsy Monitoring Unit (EMU) admission provides clinically important information in 60% to 72% of the admissions. The yield of subsequent EMU readmissions after an initial non-diagnostic first admission has not been well established. The objective of this study is to determine the diagnostic yield of repeat EMU admissions or subsequent ambulatory EEG for spell classification in patients who have had an indeterminate initial EMU admission. Methods: A retrospective chart review and analysis was conducted consisting of all EMU admissions to the Mayo Clinic Hospital Arizona between January 2007 and December 2009. Admissions for spell classification were included. Admissions for presurgical evaluation, seizure quantification and medication adjustment were excluded. The cases with indeterminate diagnoses on first EMU admission were reviewed to determine if repeat EMU admission or subsequent ambulatory EEG lead to a diagnosis. Note was made of any therapeutic changes after an indeterminate initial evaluation. Results: Total of 805 EMU admissions occurred between January 2007 and December 2009, of which 534 (66%) were for spell classification and diagnosis. 428 (80%) received a diagnosis after the first admission, leaving 106 (20%) where the diagnosis was indeterminate based on inability to record a typical event. Of the 106 indeterminate admissions, 13 (12%) went on to have a second admission. During the second admission, 8 (62%) were diagnosed. Four patients went on to have a third admission with none of them receiving a diagnosis. One patient had a fourth admission, again with no diagnosis. 19 (3%) patients had ambulatory EEG monitoring after an indeterminate admission with only one (5%) receiving a diagnosis after ambulatory EEG monitoring. Even in patients who were initially indeterminate, medication management changed 37% of the time. Conclusions: Admission to the Epilepsy Monitoring unit was helpful for spell classification and diagnosis with 80% of the patients receiving a diagnosis after the first admission. The diagnostic yield after the second EMU admission was also high at 62%. Very few patients go on to have a 3rd and 4th admissions, with none of them receiving a diagnosis. Yield for ambulatory EEG monitoring for 24-72 hours was after an indeterminate EMU admission was low. However, even in cases where a definitive diagnosis was not reached, EMU admission was still helpful, as medication management was frequently changed. After an initial indeterminate admission, a repeat EMU admission should be considered. If no diagnosis is made after the second EMU admission, subsequent admissions are unlikely to produce a definitive diagnosis.