Volumetric measurements of subcortical nuclei in patients with temporal lobe epilepsy

Objective: To determine the volumes of subcortical nuclei in patients with chronic epilepsy. Background: Animal and human data suggest a crucial role for subcortical structures in the modulation of seizure activity, mostly as seizure-suppressing relays. Although cortical epileptogenic foci can vary in localization and extent, it nevertheless appears that these structures s ubsequently influence seizure propagation in a universal fashion. There is, however, little knowledge about the size of implicated subcortical structu res in patients with epilepsy. Methods: Using high-resolution MRI, the volu mes of selected subcortical nuclei, such as the thalamus, caudate nucleus, putamen, and pallidum, were measured in both hemispheres of 27 patients wit h temporal lobe epilepsy. Fourteen healthy volunteers served as controls. S tatistical analysis was done for both normalized volumes (by total brain vo lume) and unnormalized volumes. Results: Overall, the patient group had sma ller thalamic and striatal volumes in both hemispheres, mostly ipsilateral to the epileptic focus. No significant correlations were noted between volu me measurements and age, age at onset, duration of epilepsy, or total seizu re frequency, including frequency of generalized seizures. The putamen and thalamus seemed to be affected predominantly in patients with a history of febrile convulsions, whereas patients without febrile convulsions had small er caudate nuclei bilaterally. Conclusions: Volumetric measurements of subc ortical nuclei reveal atrophy of distinct subcortical nuclei in the patient group, predominantly ipsilateral to the focus. This finding probably refle cts persistent abnormalities and not secondary change. In addition, the str uctural differences between patients with and patients without previous feb rile convulsions suggest that these conditions may have different causes.