Abstracts

Rationale: Long-term video-EEG monitoring (LTM) is the gold standard test in the definitive diagnosis of suspected epilepsy and spells of unknown nature. However, one limitation of this test is potential failure to capture typical events, leaving the diagnosis uncertain. The decision to repeat an LTM study may be aided by data supporting how often a subsequent study is successful in clarifying the diagnosis. We evaluated the value of a repeat LTM study in consecutive patients admitted to the Vanderbilt University Epilepsy Monitoring Unit (EMU) with an initial non-diagnostic study. Methods: We reviewed LTM reports for all adult patients admitted to the Vanderbilt University EMU from January 2004 to December 2005. We identified all patients who had no typical events recorded during their initial study. We recorded age, gender, number of different event types, presence of epilepsy risk factors, results of any prior MRI or EEG results, EMU days, and epileptiform and non-epileptiform interictal abnormalities. We then identified all patients who had repeat studies and recorded the EMU days and electrographic findings of the second study. Results: During the two-year period, 161/893 (18%) of all LTM studies failed to record typical events. 139 of these were first time studies. Of the individual patients who did not have any typical events during their first time studies, 18 patients (12%) were readmitted for a subsequent LTM study. Typical events were recorded in seven of them (39%): four had ictal discharges and three had non-epileptic events. One additional patient who had an atypical event on the subsequent study had interictal epileptiform discharges that were not present on the first time study. The mean length of stay was similar for both the first time and subsequent studies. Of the 11 patients who did not have any typical events during the subsequent study, two (18%) had typical events on a third LTM study with ictal discharges. There was a trend for more epilepsy risk factors and MRI abnormalities in patients with diagnostic subsequent LTM studies as compared to those whose diagnosis remained uncertain after the subsequent LTM study. Conclusions: Repeating an LTM study is successful in almost one half of patients who failed to have an event on the first study. A repeat LTM study is more likely to record ictal discharges in the presence of epilepsy risk factors and MRI abnormalities.