Abstracts

Rationale: Nocturnal frontal lobe epilepsy (NFLE) is characterized by frequent arousals from sleep with brief nocturnal motor seizures. Seizure semiology may include hyperkinetic movements with tonic or dystonic features. Ictal EEG activity at onset may show beta or theta activity in the frontal or vertex areas and frequently is difficult to localize. There is little data suggesting the precise anatomic source of these seizures. We performed Computerized Source Analysis (CSA) on seizure onsets from eight patients with NFLE to better localize the origin of their seizure activity. Methods: Eight patients (5 boys, 3 girls, 4-14 years, mean 9+/-3.6 years) with non-lesional NFLE were identified at Children's Hospital, Boston from clinical semiology of seizures and ictal EEG onset. Seizure semiology of all patients was characterized by nocturnal brief stereotypical hyperkinetic movements. Prolonged continuous EEG studies were performed on all patients. Ictal EEG recordings during typical nocturnal seizures were visually analyzed by board-certified electroencephalographers for pattern onset. EEG onsets were characterized by abrupt onset of beta or irregular theta activity in the frontal areas (bifrontal in 1, right frontal in 4, left frontal in 3.) Subsequently these onsets were closely filtered and analyzed using CSA with BESA software and a multiple dipole technique to better localize the onsets of seizures. Sources were mapped to an age-matched Montreal standard MRI to demonstrate anatomic localization. Results: We analyzed a total of 79 seizures in the eight children with CSA (range 1-30, mean 9.9+/-9.2). Seizure onset was apparent in the left frontal area in three, in the right frontal area in four, and midline frontal area in one. With CSA, sources of seizure onset were localized to the ipsilateral caudate nucleus in six of eight cases, and in the ipsilateral mesial frontal cortex in one case. For the remaining one case, EEG showed midline frontal theta activity at seizure onset, which localized to the left prefrontal cortex with CSA. This pattern was different from the source of normal spindles, localized using the same methodology. Conclusions: Non-lesional nocturnal frontal lobe epilepsy is likely an idiopathic epilepsy of childhood, for which the anatomical onset has been elusive. Using CSA, we localized the source of seizure onset in the caudate nuclei and mesial frontal cortex. Autosomal dominant NFLE has been associated with mutations in nicotinic acetylcholine receptor subunits, and such receptors are seen in the basal ganglia and the nucleus basalis of Meynert in this region. Further larger scale studies will be necessary to confirm our findings.