Abstracts

Rationale: To investigate the diagnostic yield and therapeutic relevance of outpatient video-EEG monitoring (OVEM) in intellectually disabled patients. Methods: Four-hour OVEM studies from consecutive institutionalized intellectually disabled patients were retrospectively analyzed. The diagnostic yield was assessed based on the ability of OVEM to establish the epilepsy diagnosis in terms of localization-related epilepsy (LRE) or generalized epilepsy (GE). The therapeutic relevance was assessed based on the treatment modification that occurred during the follow-up period after the OVEM. Results: There were 74 patients in the study (38 male), aged 21-75 years (mean 44 years). All patients were intellectually disabled (67 with profound and 7 with severe disability). Eighty-five OVEM studies were analyzed (9 patients had 2 studies and 1 patient had 3 studies). The patients were followed in the clinic for a mean duration of 31 months after the OVEM (range 1-56, median 31 months). Overall, OVEM was diagnostic in 54/74 (73%) of patients [LRE (n=33, 61.1%); GE (n=21, 38.9%)] and nondiagnostic in the rest (n=20, 27%). Of the 21 patients diagnosed as GE, 11 (52.4%) were consistent with Lennox-Gastaut syndrome. During the follow-up after diagnostic OVEMs (n=54), the treatment was unchanged in 9 patients who continued the same antiepileptic drugs (AEDs) while 45 patients underwent treatment modification: 35 had substitution or addition of AEDs; 2 had vagus nerve stimulator (VNS) implants; 7 had both modification of AEDs and VNS implants; 1 had a decrease in the number of AEDs (Table). Among those with nondiagnostic OVEMs (n=20), 6 patients continued the same AEDs while 14 had modification of treatment determined by their subsequent clinical course: 12 had modification of AEDs; 2 stopped AEDs altogether. The difference in treatment modification between the diagnostic and nondiagnostic groups was not statistically significant (p=0.21, Fisher’s exact test). Conclusions: Four-hour OVEM is beneficial in establishing the epilepsy diagnosis in the intellectually disabled patients. The diagnostic results of the OVEM as well as the clinical course are equally important in determining the subsequent treatment modification. Further studies are underway to determine the overall outcome with respect to seizure control after the treatment modification in this patient population.