Faculty Bibliography

OBJECTIVE: To determine the feasibility of using functional magnetic resonance imaging (fMRI) to detect asymmetries in the lateralization of memory activation in patients with temporal lobe epilepsy (TLE). BACKGROUND: Assessment of mesial temporal lobe function is a critical aspect of the preoperative evaluation for epilepsy surgery, both for predicting postoperative memory deficits and for seizure lateralization. fMRI offers several potential advantages over the current gold standard, intracarotid amobarbital testing (IAT). fMRI has already been successfully applied to language lateralization in TLE. METHODS: fMRI was carried out in eight normal subjects and 10 consecutively recruited patients with TLE undergoing preoperative evaluation for epilepsy surgery. A complex visual scene encoding task known to activate mesial temporal structures was used during fMRI. Asymmetry ratios for mesial temporal activation were calculated, using regions of interest defined in normals. Patient findings were compared with the results of IAT performed as part of routine clinical evaluation. RESULTS: Task activation was nearly symmetric in normal subjects, whereas in patients with TLE, significant asymmetries were observed. In all nine patients in whom the IAT result was interpretable, memory asymmetry by fMRI concurred with the findings of IAT including two patients with paradoxical IAT memory lateralization ipsilateral to seizure focus. CONCLUSIONS: fMRI can be used to detect asymmetries in memory activation in patients with TLE. Because fMRI studies are noninvasive and provide excellent spatial resolution for functional activation, these preliminary results suggest a promising role for fMRI in improving the preoperative evaluation for epilepsy surgery

The relationships of medical, developmental, social, and familial variables to intellectual performances (IQ scores) were assessed in a sample of 242 adult patients with intractable lateralized temporal lobe epilepsy. Lower IQ scores were associated with low patient and parent education. In addition to the significant contributions of nonneurological social and familial factors to IQ, early age at onset of regular seizures and presence of primary neurological dysfunction in the left cerebral hemisphere were also both independently related to lower IQ. The obtained results suggest that the occurrence of regular seizures during a critical period in early childhood neural maturation poses the greatest risk to cognitive development in the epilepsy population. Total duration of seizures, history of severe convulsive episodes, and the occurrence of another nonepileptic neurological problem in early childhood do not contribute significantly to delayed cognitive development

We determined both (1) the reliability (reproducibility) of seizure onset location in patients with temporal lobe recorded with extracranial EEG and (2) if interictal spike (IIS) location influences that reliability. EEGs were recorded with the 10-20 system and sphenoidal electrodes. Between 1985 and 1993, 166 patients with suspected temporal lobe epilepsy were eligible for inclusion with a total of 734 seizures recorded. Each seizure onset was classified as either localized, lateralized, or nonlocalized. Individual patients were then grouped according to interictal spike location (i.e., unilateral, bilateral, or none) as well as by ictal onset reproducibility patterns (i.e., concordant, semiconcordant, conflicting, or nonlocalized) based on each patient's monitoring session. Seizure onset location was reproducible in 68% of the cases and variable patterns of seizure onset were seen in 32% of patients. Patients with unilateral IIS (68%) were more likely to have consistent ictal onset patterns than patients with bilateral IIS (27%). The first seizure more often predicted subsequent seizure onset patterns when it was localized than when it was nonlocalized. Of 18 patients with conflicting temporal lobe seizures, up to four seizures were necessary to detect independent bilateral temporal lobe seizures