Effect of Long-term Deep Brain Stimulation of the Subthalamic Nucleus for Frontal Lobe Epilepsy: Subtraction SPECT Analysis

Shon, Young Min; Kim, Yeong In; Lee, Kyung Jin; Yang, Dong Won

Abstract

BACKGROUND
Experimental data and case reports of intractable epilepsy patients treated with deep brain stimulation (DBS) on the subthalamic nucleus (STN) suggest the considerable anticonvulsant effect. However, no satisfactory mechanisms of action have yet been elucidated. We investigated DBS's therapeutic mechanism from the cerebral perfusion changes as measured by subtracting the SPECT images. METHODS: Two patients who had previous resection on their right frontal cortices were selected for DBS of the STN. The cerebral blood flow (rCBF) changes between two SPECT images (pre-insertion and post-operatively after at least 6 months) were analyzed by SPECT subtraction with the volumetric MRI coregistration method using Analyze 5.0 software. RESULTS: After chronic STN DBS [18 months (case 1) and 6 months (case 2)], they both experienced markedly reduced seizure frequencies (86.7% reduction in patient 1, 88.6% in patient 2). In patient 1, the increased rCBF was observed in the right frontal areas (dorsolateral and inferior frontal area). Unexpectedly, there was definite hyperperfusion on the right superior and inferior temporal areas as well as rCBF increase on the right superior frontal area (SMA) in patient 2. CONCLUSIONS: We demonstrate that the cerebral perfusion increase at the irritative zones of epilepsy patients is associated with the favorable seizure reduction after STN DBS in two cases of frontal lobe epilepsy. Although its exact mechanism remains unknown, our preliminary data suggests the clinical relevance to assessing the post-procedural outcome as well as the characteristics of perfusion patterns in other epilepsy syndromes.