Abstracts

Rationale: When admitting patients for long term monitoring for epilepsy (LTME), neurologists often have a preconceived level of diagnostic suspicion based on many factors including age, gender, clinical event description, epilepsy risk factors, psychiatric comorbidities, and neuroimaging. The diagnostic yield of LTME has been previously studied, though not across different age groups. The purpose of this study is to determine the diagnostic outcome of LTME studies of adults in different age groups. The study also aims to evaluate the nature of the diagnoses, EEG findings, and neuroimaging results. Methods: We reviewed all adult admissions for LTME over a period of three months. We divided the patients into three age groups (18-40 years, 41-65 years, and >65 years). We only included LTME data on patients admitted for diagnostic purposes. We compared gender, epilepsy risk factors, duration of presumed epilepsy, comorbid psychiatric conditions, number of event types, and diagnostic outcome (epileptic, non-epileptic, or non-diagnostic). We also compared the interictal EEG abnormalities (epileptiform or non-epileptiform) during LTME and any significant MRI abnormalities. Results: A total of forty-two records were reviewed, four of which were excluded because LTME was not performed for diagnostic reasons. Of the 38 patients included in analysis, 17 patients were 18-40 years of age (28.5 ± 6.4 yrs), while 21 patients were 41-65 years of age (49.8 ± 5.8 yrs), with p<0.001. There were no patients over 65 years of age admitted during this three month period. There was no significant difference in gender, epilepsy risk factors, psychiatric comorbidities, presumed epilepsy duration, or number of event types between age groups. The percentage of patients with recorded typical events during LTME was not different in the younger (12 patients, 71 %) and older age groups (13 patients, 62 %). In the younger age group, four patients (33%) had non-epileptic diagnoses while eight patients (67%) had epileptic diagnoses. In the older age group, seven patients (54%) had non-epileptic diagnoses while six patients (46%) had epileptic diagnoses. All patients with non-epileptic seizures were given a psychogenic diagnosis, except two patients in the older age group, who were given non-psychogenic diagnoses (migraine or syncope). Patients in the younger age group tended to have more epileptiform abnormalities on EEG (41 % vs. 14 %), whereas patients in the older age group tended to have more non-epileptiform abnormalities (29% vs. 18%). None of the patients with non-epileptic diagnoses had significant MRI abnormalities. There was no difference in presence of significant MRI abnormalities among the two groups. Conclusions: Based on our preliminary analysis, the diagnostic outcomes of LTME may differ by age group. Younger adults with non-epileptic seizures tend to have a psychogenic etiology, while more of the older adults tend to have a non-epileptic, non-psychogenic diagnosis. In younger adults, the interictal EEG during LTME may be more helpful in supporting a diagnosis of epilepsy.