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

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.

Ictal Hyperperfusion of Brain Structures Related to Ictal Dystonic Posturing in Temporal Lobe Seizures

BACKGROUND: Although dystonic posturing (DP) during temporal lobe seizures is known to be related to basal ganglia activation, the mechanism of the dystonic posturing has not been investigated in greater details . METHODS: Thirty-two patients with mesial temporal lobe epilepsy (TLE) underwent ictal and interictal SPECTs. They were classified into two groups: 1) DP with ictal dystonia during ictal SPECT (N=15) and 2) Non-DP without dystonia (N=17). Ictal-interictal SPECT subtraction was performed as follows: co-registration, intensity normalization, subtraction, thresholding and then an overlay to SPGR MRI. The presence and intensity of ictal hyperperfusion were determined in frontal lobe, basal ganglia, temporal lobe and insular cortex. RESULTS: The incidences of ictal hyperperfusion in DP vs. Non-DP were caudate nucleus [80.0%(12/15 patients) vs. 0% (0/17), p=0.001], putamen [93.3% (14/15) vs. 48.2% (8/17), p=0.005], globus pallidus [53.3% (8/15) vs. 23.5% (4/17), p=0.082], thalamus [80.0% (12/15) vs. 41.2% (7/17), p=0.026], insular cortex [46.7% (7/15) vs.23.5% (4/17), p=0.051], orbitofrontal [46.7% (6/15) vs. 35.3% (7/17), p=0.053], medial frontal [6.7% (1/15) vs. 18.7% (2/17), p=0.621], dorsolateral frontal [13.3% (2/15) vs. 18.7%(2/17), p=0.737] in the hemisphere of epileptic side. In patients who showed ictal hyperperfusion in striatum and thalamus, the average intensity of hyperperfusion in DP vs. Non-DP was caudate nucleus 1.67 vs. 0.0, putamen 2.20 vs. 1.05, globus pallidus 1.2 vs. 0.65, thalamus 2.00 vs. 0.88 in the epileptic hemisphere. CONCLUSIONS: Caudate nucleus as well as putamen appeared to be important for producing ictal dystonia during TLE seizures. The greater intensity of ictal hyperperfusion in putamen, caudate nucleus and thalamus seems to be related to ictal dystonia.

Ictal Hyperperfusion of Brain Structures Related to Ictal Dystonic Posturing in Temporal Lobe Seizures

BACKGROUND: Although dystonic posturing (DP) during temporal lobe seizures is known to be related to basal ganglia activation, the mechanism of the dystonic posturing has not been investigated in greater details . METHODS: Thirty-two patients with mesial temporal lobe epilepsy (TLE) underwent ictal and interictal SPECTs. They were classified into two groups: 1) DP with ictal dystonia during ictal SPECT (N=15) and 2) Non-DP without dystonia (N=17). Ictal-interictal SPECT subtraction was performed as follows: co-registration, intensity normalization, subtraction, thresholding and then an overlay to SPGR MRI. The presence and intensity of ictal hyperperfusion were determined in frontal lobe, basal ganglia, temporal lobe and insular cortex. RESULTS: The incidences of ictal hyperperfusion in DP vs. Non-DP were caudate nucleus [80.0%(12/15 patients) vs. 0% (0/17), p=0.001], putamen [93.3% (14/15) vs. 48.2% (8/17), p=0.005], globus pallidus [53.3% (8/15) vs. 23.5% (4/17), p=0.082], thalamus [80.0% (12/15) vs. 41.2% (7/17), p=0.026], insular cortex [46.7% (7/15) vs.23.5% (4/17), p=0.051], orbitofrontal [46.7% (6/15) vs. 35.3% (7/17), p=0.053], medial frontal [6.7% (1/15) vs. 18.7% (2/17), p=0.621], dorsolateral frontal [13.3% (2/15) vs. 18.7%(2/17), p=0.737] in the hemisphere of epileptic side. In patients who showed ictal hyperperfusion in striatum and thalamus, the average intensity of hyperperfusion in DP vs. Non-DP was caudate nucleus 1.67 vs. 0.0, putamen 2.20 vs. 1.05, globus pallidus 1.2 vs. 0.65, thalamus 2.00 vs. 0.88 in the epileptic hemisphere. CONCLUSIONS: Caudate nucleus as well as putamen appeared to be important for producing ictal dystonia during TLE seizures. The greater intensity of ictal hyperperfusion in putamen, caudate nucleus and thalamus seems to be related to ictal dystonia.

Ictal Cerebral Perfusion Patterns in Partial Epilepsy: SPECT Subtraction / 대한핵의학회잡지

PURPOSE: To investigate the various ictal perfusion patterns and find the relationships between clinical factors and different perfusion patterns. MATERIALS AND METHODS: lnterictal and ictal SPECT and SPECT subtraction were performed in 61 patients with partial epilepsy. Bath positive images showing ictal hypoperfusion and negative images revealing ictal hypoperfusion were obtained by SPECT subtraction. The ictal perfusion patterns of subtracted SPECT were classified into focal hypoperfusion, hypoperfusion-plus, combined hypoperfusion-hypoperfusion, and focal hypoperfusion only. RESULTS: The concordance rates with epileptic focus were 91.8% in combined analysis of ictal hypoperfusion and hypoperfusion images of subtracted SPECT, 85.2% in hypoperfusion images only of subtracted SPECT, and 68.9% in conventional ictal SPECT analysis. Ictal hypoperfusion occurred less frequently in temporal lobe epilepsy (TLE) than extratemporal lobe epilepsy. Mesial temporal hypoperfusion alone was seen only in mesial TLE while lateral temporal hypoperfusion alone was observed only in neocortical TLE. Hippocampal sclerosis had much lower incidence of ictal hypoperfusion than any other pathology. Some patients showed ictal hypoperfusion at epileptic focus with ictal hypoperfusion in the neighboring brain regions where ictal discharges propagated. CONCLUSION: Hypoperfusion as well as hypoperfusion in ictal SPECT should be considered for localizing epileptic focus. Although the mechanisrn of ictal hypopertusion could be an intra-ictal early exhaustion of seizure focus or a steal phenomenon by the propagation of ictal discharges to adjacent brain areas, further study is needed to elucidate it.