Vascular malformations (VMs) are associated with epilepsy. The natural history of the various VMs, clinical presentation, and tendency to provoke epilepsy determine treatment strategies. Investigations have probed the mechanisms of epileptogenesis associated with these lesions. Electrophysiologic changes are associated with epileptogenic cortex adjacent to VMs. Putative pathophysiologic mechanisms of epileptogenesis include neuronal cell loss, glial proliferation and abnormal glial physiology, altered neurotransmitter levels, free radical formation, and aberrant second messenger physiology.

Summary:Purpose: To investigate ammonia and glutamine levels in valproate (VPA)-related hyperammonemic encephalopathy (VHE).Methods: We reviewed the medical records and EEG recordings of seven adults diagnosed with VHE.Results: Venous ammonia levels were elevated in five (71%) of the seven patients. Elevated serum or cerebrospinal fluid (CSF) glutamine levels were found in four (80%) of five cases tested, including two who had normal ammonia levels. Initial behavioral signs included violent outbursts in three patients, paranoid ideation severe enough to require restraint in two cases, and milder abnormalities in two instances. The severity of encephalopathy was not related to any particular serum VPA level. In four patients serum VPA levels did not exceed 100 g/ml, and in one case, VHE developed after taking only one 250-mg dose. Symptoms eventually cleared after reducing the dose of, or discontinuing, VPA. Liver-function tests were normal. Each of six patients tested had EEG findings that supported the diagnosis of VHE and excluded nonconvulsive status epilepticus. The rate of normalization of one patient's serum glutamine level and the EEGs of two cases correlated better with the timing of their delayed clinical recovery than did the more rapid rate of decline of the serum ammonia levels. Conclusions: Serum or CSF glutamine levels are initially elevated in a majority of patients with suspected VHE, sometimes in the absence of hyperammonemia. Glutamine levels may be useful adjunctive laboratory tests for the diagnosis of VHE.

Summary:Purpose: To determine whether the specific location of electrographic seizure onset in the temporal lobe is related to hippocampal pathology in temporal lobe epilepsy (TLE).Methods: Consecutive presurgical patients with scalp EEGvideo evidence of TLE and no or mild hippocampal atrophy (HA) on magnetic resonance imaging (MRI) were prospectively studied by using depth and subdural strip electrode recordings to identify the site of the initial ictal discharge (IID). Thirty-four patients had either no or mild HA (HA-group). Four additional patients with moderate or marked HA (HA+ group) who required depth and strip electrodes served as a comparison group. Hippocampal pathology was assessed by MRI volumetrics and histopathologic grade of sclerosis (HS).Results: Thirty-eight patients were investigated. In the HAgroup, 10 patients had lobar ictal EEG onsets in the hippocampus (HF), medial paleocortex (MPC), and lateral neocortex (LNC); eight cases had regional IIDs in both HF and MPC; 12 persons had IIDs completely outside the HF; three cases lacked depth electrodes, and only one case (3%) had an IID confined to the HF. By contrast, three (75%) of four HA+ cases had IIDs confined to the HF (p = 0.002). Similarly, in 12 patients with low-grade HS, IIDs confined to the HF area were seen significantly less often than in six cases with high-grade HS (p = 0.025).Conclusions: In this study of a large number of patients with no to mild and a smaller group with moderate to marked HA and HS, the location of seizure onset in the temporal lobe was related to the degree of hippocampal pathology. Absence of HA and low-grade HS was each associated with IIDs in both the hippocampus and medial (with or without lateral) temporal cortex, or only the MPC or LNC. Marked HA and high-grade HS both were associated with IIDs restricted to the HF. Key Words: EEG-Intracranial electrodes-Depth electrodes-Temporal lobe epilepsy-Pathology-Medial temporal sclerosis.Subtypes of temporal lobe epilepsy (TLE) have been proposed based on semiology, pathology, and neuroimaging findings (1-3). When hippocampal sclerosis (HS) is found in specimens from anteromesial temporal resections (AMTR), mesial TLE (MTLE) is often diagnosed (4). Occasionally, the hippocampus exhibits no or low-grade HS in AMTRs. In such instances, lateral or neocortical TLE (NTLE) may be suspected, particularly when seizures persist after resection of only MTL structures. Recent studies have begun to examine whether clinical neurophysiologic recordings can assist in differentiating MTLE from NTLE (5-10).Scalp EEG ictal discharges during temporal lobe complex partial seizures (CPSs) may consist of sequential spikes or sharp waves (11,12), but most commonly appear as rhythmic waves (13-17 (6) depth and subdural electrode recordings, Ebersole and Pacia found that scalp EEG temporal 5-to 9-Hz CPS discharges usually had ictal onset in the hippocampus, and that 2-to 5-Hz (lateralized or diffuse) extracranial ictal patterns often correlated with simultaneous ictal onset in hippocampu...

Summary:Purpose: This retrospective study reports the longterm surgical outcome of patients with medically refractory epilepsy and vascular malformations who were treated with lesionectomy. A detailed analysis of surgical failures had been performed in an attempt to define predictors of surgical success and failure.Methods: Fifteen patients with medically intractable epilepsy and angiographically occult vascular malformations (AOVMs) were treated surgically with lesionectomy at Duke University Medical Center. Lesionectomy consisted of removal of the AOVM and surrounding hemosiderin-stained brain only, without the use of electrocorticography (ECoG) to guide resection.Results: Eleven (73%) patients are seizure free after lesionectomy. Three showed no significant improvement, and one patient died, presumably after a seizure. Age of onset, duration of seizures, age at resection, and gender did not affect outcome. All patients with neocortical AOVMs in whom EEG findings correlated with the site of the lesion were seizure free after lesional resection. Treatment failures were associated with the presence of multiple intracranial lesions, poorly localized or diffuse EEG findings, discordant positron emission tomography (PET) imaging, or with a lesion in close proximity to the limbic system.Conclusions: Lesionectomy, with removal of surrounding hemosiderin-stained brain, can be considered the procedure of choice in carefully selected patients with epilepsy with occult vascular malformations.

Summary:Objective: Sex hormones can influence the timing and frequency of seizure activity. In addition, gender may influence the age of epilepsy onset and hemispheric location of focal epilepsy. Whether gender alters temporal lobe pathologies differentially is not clear. In this study, we assess if neocortical or hippocampal pathologies from patients who underwent en bloc anteriomedial temporal lobectomy (AMTR) for medically refractory epilepsy differ by gender.Method: Consecutive en bloc AMTR resections (n = 128), including hippocampal tissues, were systematically studied. Cortical and intracortical gliosis from a standardized location, 1.5 cm from the temporal lobe tip, was assessed for quantifiable gliotic change. Corresponding hippocampal sections were characterized according to Watson grade. These outcomes were then compared by gender. Other correlates such as age of epilepsy onset, age of risk exposure, and duration of epilepsy were similarly compared.Results: Subpial and intracortical gliosis was more pronounced in women (p = 0.02, p < 0.01). Cortical thickness was reduced in women compared to men (p < 0.05). No similar gender effects were seen in Watson grade of hippocampal sclerosis or CA1-4 neuronal dropout.Conclusions: Gender may differentially influence neocortical pathologies in patients with refractory temporal lobe epilepsy. No gender effect was seen when studying hippocampal pathologies.