Dr. Gregory Worrell discusses his study of patients with refractory epilepsy. The study is being presented at the Amercian Academy of Neurology Annual Meeting.
Abstract
OBJECTIVE: To determine the correlation between surgical outcome and ictal onset patterns recorded with intracranial electroencephalography (iEEG) in a cohort of patients with medically refractory epilepsy
BACKGROUND: Numerous factors have been analyzed in attempts to predict the outcome of epilepsy surgery. However, the relationship between ictal onset EEG patterns and outcome has yet to be elucidated
DESIGN/METHODS: We analyzed 196 iEEG recorded seizures obtained from 61 patients who had undergone intracranial monitoring and surgery. Seizure onset was defined within the first second of a localized, sustained EEG pattern that was visually distinguished from background activity. Ictal onset patterns were characterized by the frequency, morphology and spatial distribution of the seizure discharge. A good surgical outcome was defined as per international league against epilepsy (ILAE) class 1-3. The duration of follow-up was 1-7 years
RESULTS: Of the sixty-one patients, 22 patients had temporal lobe epilepsy, 29 frontal, 6 parietal and 4 occipital. Forty-four patients (72%) had lesions on MRI. The most common pathology was nonspecific gliosis (41), MTS (3), cortical dysplasia (9), and tumor (8). A good outcome was reported by 42 patients (68%). The ictal onset pattern consisting of low voltage fast activity was a strong predictor of good surgical outcome, while a rhythmic sinusoidal activity or spike waves were associated with poor outcome (90.9% v.s. 56.41%, P=0.005). In addition, the ictal onset rhythm of gamma or beta frequency (>12Hz) was more likely to be associated with a favorable outcome (85.71 % Vs 46.15 %, P=0.001). The restriction of ictal onset to a focal distribution (5 electrodes or less) showed a trend toward a better outcome (71.43 Vs 28.57, P=0.06).
CONCLUSIONS/RELEVANCE: High frequency ictal onset and focal spatial distribution are associated with a favorable outcome after surgery. Further studies are required to understand the underlying pathophysiology of the good outcome in these selected groups of patients
Authors: Tarek Zakaria, MD Terrence Lagerlund, MD Elson So, MD Gregory Worrell, MD Mayo Clinic
