Abstracts

Experimental data and case reports of intractable epilepsy patients treated with DBS of STN suggest the considerable anticonvulsant effect. But, no satisfactory mechanisms of the action have been elucidated yet. We investigated its therapeutic mechanism from the perfusion changes measured by subtraction SPECT image of pre-insertion state from that of the chronic post-insertion period. Case 1: A 23-year-old female patient who had previous resective surgery on right frontal cortex with anterior callosotomy four years ago was selected for DBS of STN. She showed frequent bilateral asymmetric tonic seizures (left [gt] right) with rare drop attacks and her seizure frequency was 15/month in the pre-insertion period. Interictal spikes were seen in the bilateral frontal areas with right dominance (F2, FC2, F4 maximum, 149 per 3 minutes). Her AED medication was VPA 1200mg, CBZ 400mg, TPM 300mg, Oxcarbazepine 600mg /D. After starting STN DBS, the number of seizures was slowly decreased. At the moment of 18 months after stimulation on, she experienced only two seizures per month (86.7% reduction), with decreased severity and duration and interictal spikes was also decreased (48.6% reduction). Valproate and oxcarbazepine was successfully discontinued as well. Case 2: A 22-year-old male patient was admitted for DBS of STN. He had also right cortical resection with invasive study from the frequent brief, hypermotor seizure with fencing posture originated from right supplementary motor area (SMA). But he showed unsatisfactory outcome after incomplete resection of extensive epileptogenic zone. The seizure frequency was 2.5/day under six AED regimen. Six months after STN DBS, he showed only two seizures a week (88.6% reduction) and slight reduction of AED dosage was permitted. After chronic STN DBS [18 months after (case 1) and 6 months (case 2)], SPECT subtraction with volumetric MRI coregistration was performed using Analyze 5.0 software. In case 1, the brain perfusion was increased in bilateral frontal areas (bilateral SMA with right dominance and right dorsolateral frontal area) after STN DBS. Case 2 showed unexpected hyperperfusion on right insular cortex and inferior temporal areas as well as definite perfusion increase in right SMA. We demonstrate that the cerebral perfusion increase at the irritable zones of epilepsy patients is associated with the favorable seizure reduction after STN DBS in two cases of frontal lobe epilepsy. Although its exact mechanisms remain unknown, it suggests that the perfusion changes after STN DBS in frontal lobe epilepsy patients is quite different from those in subjects with Parkinson[rsquo]s disease. This preliminary data suggests the relevance to assessing their post-procedural outcome as well as the characteristics of perfusion patterns in other epilepsy syndromes.