David Marks

Migraine‐related seizures in adults with epilepsy, with EEG correlation

We studied the relationship between migraine and epilepsy in 395 adult seizure patients. Seventynine patients (20%) also had migraine syndrome, and 13 of these patients (3%) experienced seizures during or immediately following a migraine aura. Patients with catamenial epilepsy and patients with migraine with aura were at an increased risk for an association between these two disorders. In two patients, we recorded the entire sequence from migraine aura to partial seizure, and in both there were distinctive changes on the EEG during the migraine aura that preceded the onset of an electrographic complex partial seizure. Periodic lateralized epileptiform discharges were recorded in five other patients in close temporal relation to their migraine attacks. There was improved seizure control with combination antimigraine and antiepileptic drugs (AEDs) in six patients who failed to respond to AEDs alone.

Frontal lobe partial seizures and psychogenic seizures Comparison of clinical and ictal characteristics

Of all partial seizures, those of frontal lobe origin (FLPS) are most bizarre and are often mistaken for psychogenic seizures (PS). The reverse can also be true. To clarify the confusing clinical presentation of these different seizure types, we compared the clinical ictal characteristics of 63 FLPS in 11 patients with 29 PS in 12 patients. Patients with PS had significantly later age at onset and longer ictal duration. There was no statistically significant difference between the two groups with respect to history of psychiatric disorder, ictal pelvic thrusting, rocking of body, side-to-side head movements, or rapid postictal recovery, all of which previously have been reported as characteristic features of PS. Turning to a prone position during the seizure occurred only in FLPS. Nocturnal occurrence, short ictal duration, younger age at onset, stereotyped patterns of movements, and MRI and EEG abnormality suggested FLPS.

Characteristics of intractable seizures following meningitis and encephalitis.

We studied clinical seizure characteristics, seizure localization, and pathology in 38 patients who developed medically intractable partial seizures following meningitis (n = 16) or encephalitis (n = 22) and were evaluated for epilepsy surgery. Whereas meningitis in this group was commonly associated with mesial temporal sclerosis (MTS), most encephalitis patients had neocortical foci. The age of onset of the encephalitic illness was important in predicting mesial temporal or neocortical foci in that group: encephalitis before, but not after, age 4 years was associated with MTS. Since almost all meningitis occurred before age 4 years, these data support the hypothesis that the medial temporal lobe is particularly susceptible to early insults, establishing the initial pathologic entity of MTS and the subsequent cascade of partial seizures. Later-onset encephalitis produced extrahippocampal neocortical seizure foci, was rarely associated with MRI abnormality, and was difficult to localize precisely. In contrast, meningitis was commonly associated with MTS, aiding seizure localization and successful surgical intervention when seizures were medically uncontrolled.

Seizure localization and pathology following head injury in patients with uncontrolled epilepsy

We studied seizure localization and surgical pathology in 25 patients who developed intractable complex partial seizures following head trauma. All patients underwent an extensive presurgical evaluation that included MRI, neuropsychological evaluation, and surface EEG monitoring, and 21 had intracranial EEG monitoring. Seizures were successfully localized in nine patients; all nine underwent a surgical procedure and are seizure-free. Six of these patients had a mesial temporal lobe seizure focus, of whom five had a pathologic diagnosis of mesial temporal sclerosis. All five patients who developed mesial temporal sclerosis sustained their head injury at or before age 5 years. The three remaining patients whose seizures were successfully localized had neocortical foci and circumscribed radio-graphic abnormalities, which were presumed to be secondary to head trauma, and all had successful surgical resections of the epileptogenic focus. The remaining 16 patients sustained later trauma and did not have a focal MRI lesion, and their seizures were not adequately localized. We conclude that as a group, seizure foci secondary to head trauma are difficult to localize accurately, and this should deter surgical intervention. There was an association between early head injury (ie, at or before age 5 years) and mesial temporal sclerosis, and this association aided seizure localization and successful surgical intervention. Therefore, under the right circumstances, trauma can be a suitable historical element in the profile of patients in whom epilepsy surgery is successful.

Significance of Spikes Recorded on Intraoperative Electrocorticography in Patients with Brain Tumor and Epilepsy

Summary: Purpose: Patients with medically intractable epilepsy due to brain tumors may undergo resective surgery for treatment of both the tumor and the epilepsy. In this instance, the extent of surgical resection is sometimes guided by spikes recorded on intraoperative electrocorticography (ECoG). Whether spikes recorded by electrocorticography imply active epileptogenicity has not been addressed adequately.

Comparison and correlation of surface and sphenoidal electrodes with simultaneous intracranial recording: an interictal study

We prospectively compared and correlated interictal spikes recorded with simultaneous surface, sphenoidal, depth and subdural electrodes in 21 patients. Although the amplitude of sphenoidal spikes was often larger than that of surface spikes in patients with mesial basal temporal ictal and interictal foci, only 1 patient had exclusively sphenoidal spikes. Spikes with maximal amplitude at the sphenoidal electrode arose from mesial temporal, temporal neocortical and orbital frontal foci. An inferior vertical temporal dipole (hippocampal positive and inferior temporal neocortex negative) was associated with surface and sphenoidal spikes.

Anatomic Correlates of Interhippocampal Seizure Propagation Time

Summary: The relation between interhippocampal seizure propagation time (IHSPT) and anatomic alterations in the human epileptic hippocampus may provide insight into the pathophysiology of temporal lobe epilepsy (TLE). Using depth electrode recordings, we measured the time required for spontaneous seizures with onset in one hippocampus to become manifest in the contralateral hippocampus in 50 patients who underwent resection of the temporal lobe of seizure origin. Cell densities in individual hippocampal subfields were determined and correlated with mean IHSPT for each patient. Mean IHSPT was significantly and inversely correlated with cell counts in CA4 only (r =−0.38, p < 0.01, Pearsons product correlation; r =−0.52, p < 0.001, Spearmans rank order correlation). In 5 patients with bilateral independent hippocampal seizure onset who had temporal lobectomy and a diagnosis of mesial temporal sclerosis, mean IHSPT was consistently longer from the sclerotic temporal lobe than to it. These observations suggest that anatomic changes associated with chronic epilepsy alter propagation patterns. Because CA4 is believed to modulate the output of dentate granule cells and also has commissural connections to the contralateral homotopic area, the association of decreased CA4 cells with prolongation of IHSPT suggests that the observed anatomic alterations may actively (through increased inhibition) or passively (through decreased recruitment) interfere with various routes of seizure propagation.

Clinical and electrographic effects of acute anticonvulsant withdrawal in epileptic patients

We retrospectively investigated the effects of acute antiepileptic drug (AED) withdrawal on seizure symptomatology—including frequency, clinical features, and electrical onset—by studying 35 patients during evaluation for epilepsy surgery. The highest risk for both partial and secondary generalized seizures occurred during absent or subtherapeutic, and not during rapidly falling, AED levels. AED withdrawal had minimal effect on clinical symptomatology or electrographic onset.

Standardization of Amygdalohippocampectomy with Intraoperative Magnetic Resonance Imaging : Preliminary Experience

Summary:  Purpose: Intraoperative magnetic resonance imaging (IMRI) is an extremely useful neurosurgical tool in surgeries in which the extent of resection is known to have a significant impact on outcome. Residual hippocampus is the most common cause of recurrent seizures after temporal lobectomy for medial temporal lobe epilepsy. Although the risk/benefit ratio of a policy of universal radical hippocampal resection is not known, we hypothesized that IMRI would aid in the intraoperative assessment of the extent of hippocampal resection and assist in accomplishing a complete hippocampectomy.