Quantitative magnetic resonance imaging in temporal lobe epilepsy: Relationship to neuropathology and neuropsychological function

Abstract

Magnetic resonance images (MRIs) were obtained from 25 patients with medically refractory epilepsy of temporal lobe origin (12 on the left, 13 on the right) and 14 right-handed control subjects. The hippocampi and temporal lobes were traced by computer on successive coronal images and the resulting measurements of area were summed for each region. The left and right hippocampi were symmetrical in the control subjects; however, for patients the hippocampus was smaller on the side of the seizure focus. Moreover, the left-right hippocampal ratio significantly differentiated the control subjects from each patient group. The left temporal lobe was significantly smaller than the right in control subjects. The epileptics' temporal lobes were smaller on the side of the seizure focus, compared to the temporal lobes in the control subjects. MRI hippocampal measurements were compared to hippocampal neuronal densities obtained postoperatively. Significant correlations were obtained between the ratio (side ipsilateral to focus/side contralateral to focus) of MRI hippocampal measurements and neuronal densities in all hippocampal subfields except CA2. Prior to surgery, patients were administered the Wechsler Memory Scale and the verbal Selective Reminding Test. Significant correlations existed between MRI measurements of the left hippocampus and the Wechsler logical memory percent retention scores and between the left temporal lobe measurements and the verbal Selective Reminding Test scores for patients with seizure foci in the left temporal lobe.

Thalamic atrophy and cognition in unilateral temporal lobe epilepsy

“…Overall, thalamic volume was a stronger correlate of both memory and nonmemory cognitive functioning than hippocampal volume. Similar to several other reports, a smaller left hippocampus was significantly associated with poorer verbal memory performance and hippocampal volume in the right TLE group did not show any significant association with cognition (Bonilha et al, 2007;Griffith et al, 2004;Lencz et al, 1992;Rausch et al, 1994). However, hippocampal volume (either left or right) was not significantly correlated with the nonmemory neuropsychological indices.…”

The use of neuroimaging to study behavior in patients with epilepsy

“…Initial studies focused exclusively on hippocampal volumes and their relationship to memory dysfunction in temporal lobe epilepsy (TLE) ((1-3), for a review, see (4)). These studies demonstrated a consistent relationship between reductions in left hippocampal volume, or hippocampal asymmetries, and impairments in verbal learning and memory, in TLE patients who were left-hemisphere dominant for language (1,2,(5)(6)(7)(8)(9). More importantly, these studies established that patients without left hippocampal volume loss were at greatest risk for postoperative memory decline (7).…”

Correlation of Hippocampal Glucose Oxidation Capacity and Interictal FDG‐PET in Temporal Lobe Epilepsy

“…It has been proposed that FDG-PET hypometabolism is closely associated with the presence of underlying MTS and correlates with the degree of hippocampal volume loss measured by means of volumetric MRI (8,9,26). Conversely, several studies failed to show a clear relation between hippocampal neuronal cell loss, which is correlated with hippocampal atrophy, and interictal FDG-PET hypometabolism (10)(11)(12).…”