Disconnection of hippocampal networks contributes to memory dysfunction in individuals with temporal lobe epilepsy.

A deficit in declarative memory function is common among individuals with temporal lobe epilepsy. The purpose of this study is to evaluate the relationship between the volume of the hippocampus, entorhinal cortex along with the surrounding parahippocampal white matter and memory performance in those with temporal lobe epilepsy. T1 weighted MRI scans were acquired using a 3-D pulse sequence in 50 individuals with temporal lobe epilepsy. Hippocampal and entorhinal cortex volumes were derived by manually tracing consecutive coronal slices aligned perpendicular to the long axis of the hippocampus. In addition, parahippocampal white matter volumes were determined using voxel based morphometry. Finally, declarative memory was assessed using immediate and delayed verbal and visual memory tests from the Wechsler Memory Scale third edition. Significant correlations were seen between right and left hippocampal volumes and delayed verbal memory test scores. In addition, left parahippocampal white matter showed positive correlations with immediate and delayed verbal and visual recall. Furthermore, regression models found that the right hippocampus and left parahippocampal white matter were the best predictors of immediate and delayed verbal and visual memory performance. These results show that a decrease in white matter fibers projecting to the hippocampus may cause a disruption of incoming multi-modal sensory information, contributing to the memory decline seen in individuals with temporal lobe epilepsy.

The measurement of ammonia blood levels in patients taking valproic acid: looking for problems where they do not exist?

Hyperammonemia (HA) commonly occurs with the use of valproic acid (VPA); while it has no clinical significance in most cases, the Physician Desk Reference recommends its discontinuation in the presence of HA. The purpose of this study is to review the literature in order to estimate the prevalence and magnitude of HA in VPA treated patients, to establish any association with hepatotoxicity and encephalopathy and to identify any factors associated with its occurrence. A search of MEDLINE and Cochrane Database of Systematic Reviews, between 1980 and 2005 was performed. Out of 183 studies, 24 met our inclusion criteria. The prevalence of HA in the prospective studies ranged between 70% and 100%, while in cross-sectional studies it varied between 16% and 100%. Ammonia (NH(3)) blood levels increased by a two-fold average relative to the baseline levels. There was no association between HA and clinical symptoms. Concomitant administration of other antiepileptic drugs (AEDs) was the factor most frequently associated with HA.