Abstracts

RATIONALE: Quantitative MR imaging displays volume reduction in the entorhinal and temporopolar cortices ipsilateral to the seizure onset in subpopulations of patients with drug-resistant TLE. This study investigates whether damage to these extrahippocampal medial temporal lobe cortical areas contributes to memory dysfunction in TLE.
METHODS: The control group consisted of 20 healthy individuals (10f, 10m) with a mean age of 32[plusminus]9 y. Altogether 45 patients (22f, 23m; mean age 33[plusminus]10y) with unilateral TLE were scanned with 1.5 T Magnetom. Quantitative volumes of the hippocampus, as well as entorhinal, perirhinal, and temporopolar cortices were assessed. Neuropsychologic evaluation of verbal memory included delayed story recall (DSR) and delayed recall of paired associates. Assessment of visual memory included WMS delayed recall of figures (DRF) and delayed recall of the Rey-Osterrieth complex figure. All patients were subsequently operated on
RESULTS: In left TLE (n=22), the mean volume of the left hippocampus was reduced by 32% (p[lt]0.01), the mean volume of the left entorhinal cortex by 19% (p[lt]0.01), and the mean volume of the left temporopolar cortex by 20% (p[lt]0.01) when compared to that in controls. In right TLE (n=23) the mean volume of the right hippocampus was reduced by 26% (p[lt]0.01) and the right entorhinal cortex by 10% (p[lte]0.01) when compared to controls. All contralateral cortical volumes were unaffected. There was a correlation between the performance in delayed recall of paired associates and left hippocampal (r=0.335, p[lt]0.05), left entorhinal (r=0.348, p[lt]0.05) or left temporopolar (r=0.340, p[lt]0.05) volume. Respectively, performance in the delayed recall of the Rey-Osterrieth complex figure correlated with the right entorhinal volume (r=0.401, p[lt]0.05), but not with right hippocampal volume.
CONCLUSIONS: This study suggests that in human TLE a decrease in the volume of left entorhinal and temporopolar cortices is associated with verbal memory impairment. Reduction in the volume of the right entorhinal cortex associates with visual memory impairment. Patients with TLE are, however, a heterogeneous group in terms of etiology, seizure frequency, medication, and other demographic parameters. The correlation analyses do not take into account other possible contributing and confounding factors. Therefore, further assessment with multivariate analyses is needed to specify the contribution of each of the medial temporal lobe structures to cognitive decline in TLE.
[Supported by: The Academy of Finland, the Kuopio University Hospital Research Fund, the North-Savo Regional Fund of the Finnish Cultural Foundation, the University of Kuopio, and the Vaajasalo Foundation]