Intracranial electrographic analysis of preictal spiking and ictal onset in uni- and bitemporal epilepsy.

AIM: Ictal onset patterns in bilateral mesial temporal lobe epilepsy have not been comprehensively studied. A retrospective review of intracranial electrographic data was undertaken to establish whether it is possible to distinguish between unilateral and bilateral mesial temporal lobe epilepsy based on ictal onset patterns, including periodic preictal spiking. METHODS: A total of 470 ictal onset patterns were analyzed by bitemporal extraoperative electrocorticography in 13 patients with medically intractable mesial temporal lobe epilepsy. Ictal onset patterns were categorized, by frequency, as type A (<12 Hz), type B (12-40 Hz) and type C (>40 Hz). Preictal rhythmic spiking, of at least five seconds duration, and time to contralateral propagation were also measured with each ictal event. We determined if the proportion of "ictal onset pattern frequencies" or "incidence of preictal spiking" differed between unilateral and bilateral mesial temporal lobe epilepsy. RESULTS: Seven patients with unilateral mesial temporal lobe epilepsy received surgery and achieved Engel class I outcomes, while the remaining six did not undergo resective surgery, due to the bilateral ictal onsets in extraoperative electrocorticography. The proportion of patients experiencing any preictal spikes was higher in unitemporal than in bitemporal cases (100% vs 50%;p=0.069). Ofthe470 ictal onset patterns analyzed (174 unitemporal and 296 bitemporal), a significant greater percentage of preictal spikes was found in unilateral cases (78% unitemporal vs 14% bitemporal; p=0.002). Low-frequency patterns were more evident in bitemporal cases (45%) than in unitemporal (10%), although the difference was not statistically significant (p=0.129). No differences were detected between the unitemporal and bitemporal groups regarding age at onset or at presentation. CONCLUSION: A greater proportion of pre ictal spiking, based on extraoperative electrocorticography, was present in unilateral, compared to bilateral, mesial temporal lobe epilepsy. Further studies are warranted to determine the causal significance of preictal spiking in mesial temporal lobe epilepsy.

Influence of age and location of ictal onset on postoperative outcome in patients with localization-related epilepsy.

INTRODUCTION: Localization-related epilepsy is a significant concern for the middle-aged and older population given the lesser cognitive reserve and the greater likelihood of adverse systemic antiepileptic drug effects. Epilepsy surgery for this age group has the potential for greater postoperative morbidity and mortality, a protracted rehabilitation with its associated economic burden, progressive cognitive and memory decline and a lesser chance of becoming seizure-free after the procedure. METHODS: A retrospective institutional archival review of 120 patients with medically refractory partial epilepsy of both temporal and extratemporal epilepsy was performed. Comparative assessments for seizure cessation and neuropsychological effects were made for those younger and older than 50 years and those with epilepsy durations of greater and less than 20 years. RESULTS: A comparison of surgical outcomes by age group identified that Engel Class I outcomes were attained in 26 of 35 (74%) patients in the older group compared with 49 of 85 (58%) patients in the younger group (p = 0.087). Of the 11 patients aged 60 years or older, 91% attained an Engel Class I outcome, significantly higher than those under 60 years (60%; p = 0.041). Stratification by age of the entire group, otherwise, demonstrated no significant differences by Engel class outcome. Considering both transient and permanent disabilities, the overall complication rate was 14.2% and was similar in patients less than 50 years of age (15.3%) and those aged 50 years or greater (11.4%; p = 0.58). Verbal memory decline was more notable in the older population and for those with epilepsy duration of greater than 20 years. CONCLUSION: This study demonstrates that epilepsy surgery in the older population has similar seizure-free outcomes and complications when compared with younger patients for both mesial temporal and extratemporal origins. Caution regarding postoperative memory decline in the older population must be stressed.

Ictal barking as a manifestation of temporal lobe epilepsy.

Ictal nonspeech vocalizations have been described as manifestations of either frontal or temporal epileptogenicity originating mainly from the dominant hemisphere. Ictal barking, particularly, has been considered a manifestation of mesial frontal epilepsy. A 42-year-old right-handed male with posttraumatic drug-resistant complex partial epilepsy manifested ictal barking near electrographic onset. Extraoperative electrocorticography with subdural electrode coverage of the right frontoparietal and temporal and left frontal surfaces provided surveillance of ictal origin and propagation. Ictal origin was identified in the right mesial temporal lobe with barking vocalization manifesting within 3s of electrographic onset. No subsequent spread of activity was noted beyond the temporal lobe. Resection of the mesial temporal structure resulted in seizure freedom. Pathology identified hippocampal sclerosis. This case supports the notion that an intrinsic, intralobar epileptogenic neural network in either hemisphere can act as a conduit into the limbic and memory circuits without a laterality bias to manifest as barking.

Periictal diffusion abnormalities of the thalamus in partial status epilepticus.

PURPOSE: To identify and describe thalamic dysfunction in patients with temporal as well as extratemporal status epilepticus (SE) and to also analyze the specific clinical, radiological, and electroencephalography (EEG) characteristics of patients with acute thalamic involvement. METHODS: We retrospectively identified patients who presented with clinical and electrographic evidence of partial SE and had thalamic abnormalities on diffusion-weighted imaging (DWI) within 5 days of documentation of lateralized epileptiform discharges (group 1). The spatial and temporal characteristics of the periodic lateralized epileptiform discharges (PLEDs) and the recorded electrographic seizures were analyzed and correlated with magnetic resonance imaging (MRI)-DWI hyperintense lesions. The findings of group 1 patients were compared with those of patients with partial SE without thalamic abnormalities on DWI (group 2). RESULTS: The two groups were similar with regard to clinical presentation and morphology of epileptiform discharges. Group 1 patients had thalamic hyperintense lesions on DWI that appeared in the region of the pulvinar nucleus, ipsilateral to the epileptiform activity. Statistically significant relationship was noted between the presence of thalamic lesions and ipsilateral cortical laminar involvement (p = 0.039) as well as seizure origin in the posterior quadrants (p = 0.038). A trend towards PLEDs originating in the posterior quadrants was also noted (p = 0.077). DISCUSSION: Thalamic DWI hyperintense lesions may be observed after prolonged partial SE and are likely the result of excessive activity in thalamic nuclei having reciprocal connections with the involved cortex. The thalamus likely participates in the evolution and propagation of partial seizures in SE.