• The Korean Journal of Nuclear Medicine
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• v.29 no.4
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• pp.445-450
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• 1995

The epileptogenic zones should be localized precisely before surgical resection of these zones in intractable epilepsy. The localization is more difficult in patients with neocortical epilepsy than in patients with temporal lobe epilepsy. This study aimed at evaluation of the usefulness of ictal brain perfusion SPECT for the localization of epileptogenic zones in neocortical epilepsy. We compared the performance of ictal SPECT with MRI referring to ictal scalp electroencephalography(sEEG). Ictal $^{99m}Tc$-HMPAO SPECT were done in twenty-one patients. Ictal EEG were also obtained during video monitoring. MRI were reviewd. According to the ictal sEEG and semiology, 8 patients were frontal lobe epilepsy, 7 patients were lateral temporal lobe epilepsy, 2 patients were parietal lobe epilepsy, and 4 patients were occipital lobe epilepsy. Ictal SPECT showed hyperperfusion in 14 patients(67%) in the zones which were suspected to be epileptogenic according to ictal EEG and semiology. MRI found morphologic abnormalities in 9 patients(43%). Among the 12 patients, in whom no epileptogenic zones were revealed by MRI, ictal SPECT found zones of hyperperfusion concordant with ictal SEEG in 9 patients(75%). However, no zones of hyperperfusion were found in 4 among 9 patients who were found to have cerebromalacia, abnormal calcification and migration anomaly in MRI. We thought that ictal SPECT was useful for localization of epileptogenic zones in neocortical epilepsy and especially in patients with negative findings in MRI.

• The Korean Journal of Nuclear Medicine
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• v.37 no.1
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• pp.24-33
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• 2003

Finding epileptogenic zone is the most important step for the successful epilepsy surgery. F-18 fluorodeoxyglucose positron emission tomography (FDG-PET) and single photon emission computed tomography (SPECT) can be used in the localization of epileptogenic foci. In medial temporal lobe epilepsy, the diagnostic sensitivity of FDG-PET and ictal SPECT is excellent. However, detection of hippocampal sclerosis by MRI is so certain that use of FDG-PET and ictal SPECT in medial temporal lobe epilepsy is limited for some occasions. In neocortical epilepsy, the sensitivities of FDG-PET or ictal SPECT are fair. However, FDG-PET and ictal SPECT can have a crucial role in the localization of epileptogenic foci for non-lesional neocortical epilepsy. Interpretation of FDG-PET has been recently advanced by voxel-based analysis and automatic volume of interest analysis based on a population template. Both analytical methods can aid the objective diagnosis of epileptogenic foci. Ictal SPECT was analyzed using subtraction methods and voxel-based analysis. Rapidity of injection of tracers, ictal EEG findings during injection of tracer, and repeated ictal SPECT were important technical issues of ictal SPECT. SPECT can also be used in the evaluation of validity of Wada test.

• Nuclear Medicine and Molecular Imaging
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• v.41 no.2
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• pp.97-101
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• 2007

Correct localization of epileptogenic zone is important for the successful epilepsy surgery. Both ictal perfusion single photon emission computed tomography (SPECT) and interictal F-18 fluorodeoxyglucose positron emission tomography (FDG-PET) can provide useful information in the presurgical localization of intractable partial epilepsy. These imaging modalities have excellent diagnostic sensitivity in medial temporal lobe epilepsy and provide good presurgical information in neocortical epilepsy. Also provide functional information about cellular functions to better understand the neurobiology of epilepsy and to better define the ictal onset zone, symptomatogenic zone, propagation pathways, functional deficit zone and surround inhibition zones. Multimodality imaging and developments in analysis methods of ictal perfusion SPECT and new PET ligand other than FDG help to better define the localization.

• Nuclear Medicine and Molecular Imaging
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• v.42 no.sup1
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• pp.172-176
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• 2008

FDG PET has been used as a diagnostic tool for localization of seizure focus for last 2-3 decades. In this article, the clinical usefulness of FDG PET in the management of patients with epilepsy has been reviewed, which provided the evidences to justify the medicare reimbursement for FDG PET in management of patients with epilepsy. Literature review demonstrated that FDG PET provides an important information in localization of seizure focus and determination whether a patients is a surgical candidate or not. FDG PET has been reported to have high diagnostic performance in localization of seizure focus in neocortical epilepsy as well as temporal lobe epilepsy regardless of the presence of structural lesion on MRI. Particularly, FDG PET can provide the additional information when the results from standard diagnositic modality such as interictal or video-monitored EEG, and MRI are inconclusive or discordant, and make to avoid invasive study. Furthermore, the presence of hypometabolism and extent of metabolic extent has been reported as an important predictor for seizure free outcome. However, studies suggested that more accurate localization and better surgical outcome could be expected with multimodal approach by combination of EEG, MRI, and functional studies using FDG PET or perfusion SPECT rather than using a single diagnostic modality in management of patients with epilepsy. Complementary use of FDG PET in management of epilepsy is worth for good surgical outcome in epilepsy patients.

• Journal of Korean Neurosurgical Society
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• v.30 no.11
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• pp.1300-1307
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• 2001

Purposes : This study reports the possible causes of seizure recurrence in patients underwent previous epilepsy surgery, and surgical strategy for resection of the additional epileptogenic zone locating at the distant area to the site of first resection. Methods : A total of 10 patients with previous surgery due to intractable epilepsy were studied. Five of these underwent standard temporal lobectomy, four extratemporal resection, and one corticoamygdalectomy. Seizure outcome of these were class III-IV. Evaluation methods for reoperation included MRI, 3D-surface rendering of MRI, PET, prologned video-EEG recording with surface electrodes and subdural grid electrodes. Additional resection was done in the frontal lobe in two, in the temporal lobe in three, in the parietal lobe in two, and in the supplementary sensori-motor area in two. Tumor in the superior frontal gyrus in the left hemisphere was removed in one patient. Extent of resection was decided based on the results of ictal subdural grid EEGs and MRI findings. Awake anesthesia and electrocortical stimulation were performed in the two patients for defining the eloquent area. Results : Histopathologic findings revealed extratemporal cortical dysplasia in six, hippocampal sclerosis and cortical dysplasia of the temporal neocortex in one, neuronal gliosis in two, and meningioma in one. Previous pathology of the five patients with cortical dysplasia in the second operation was hippocampal sclerosis plus cortical dysplasia of the temporal neocortex. After reoperation, seizure outcomes were class I in six, class II in three, class III in one at the mean follow-up period of 17.5 months. Characteristically, patients in class II-III after reoperation showed histopathologic findings of hippocampal sclerosis plus temporal neocortical cortical dysplasia plus extratemporal cortical dysplasia. Conclusions : Seizure recurrence after epilepsy surgery was related with the presence of an additional epileptogenic zone distant to the site of first operation, and the majority of the histopathology of the surgical specimens was cortical dysplasia. In particular, hippocampal sclerosis plus temporal neocortical cortical dysplasia was highly related with seizure recurrence in patients with previous operation. In these patients, multimodal evaluation methods were necessary in defining the additional epileptogenic zone.

• The Korean Journal of Nuclear Medicine
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• v.32 no.1
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• pp.20-31
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• 1998

A robust algorithm to disclose and display the difference of ictal and interictal perfusion may facilitate the detection of ictal hyperfusion foci. Diagnostic performance of localizing epileptogenic zones with subtracted SPECT images was compared with the visual diagnosis using ictal and interictal SPECT, MR, or PET. Ietal and interictal Tc-99m-HMPAO cerebral perfusion SPECT images of 48 patients(pts) were processed to get parametric subtracted images. Epileptogenic foci of all pts were diagnosed by seizure free state after resection of epileptogenic zones. In subtraction SPECT, we used normalized difference ratio of pixel counts(ictal-interictal)/interictal ${\times}100%$) after correcting coordinates of ictal and interictal SPECT in semi-automatized 3-dimensional fashion. We found epileptogenic zones in subtraction SPECT and compared the performance with visual diagnosis of ictal and interictal SPECT, MR and PET using post-surgical diagnosis as gold standard. The concordance of subtraction SPECT and ictal-interictal SPECT was moderately good(kappa=0.49). The sensitivity of ictal-interictal SPECT was 73% and that of subtraction SPECT 58%. Positive predictive value of ictal-interictal SPECT was 76% and that of subtraction SPECT was 64%. There was no statistical difference between sensitivity or positive predictive values of subtraction SPECT and ictal-interictal SPECT, MR or PET. Such was also the case when we divided patients into temporal lobe epilepsy and neocortical epilepsy. We conclude that subtraction SPECT we produced had equivalent diagnostic performance compared with ictal-interictal SPECT in localizing epileptogenic zones. Additional value of these subtraction SPECT in clinical interpretation of ictal and interictal SPECT should be further evaluated.

• The Korean Journal of Nuclear Medicine
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• v.34 no.3
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• pp.169-182
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• 2000

Purpose: To investigate the various ictal perfusion patterns and find the relationships between clinical factors and different perfusion patterns. Materials and Methods: Interictal and ictal SPECT and SPECT subtraction were performed in 61 patients with partial epilepsy. Both positive images showing ictal hyperperfusion and negative images revealing ictal hypoperfusion were obtained by SPECT subtraction The ictal perfusion patterns of subtracted SPECT were classified into focal hyperperfusion, hyperperfusion-plus, combined hyperperfusion-hypoperfusion, and focal hypoperfusion only. Results: The concordance rates with epileptic focus were 91.8% in combined analysis of ictal hyperperfusion and hypoperfusion images of subtracted SPECT, 85.2% in hyperperfusion 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 hyperperfusion alone was seen only in mesial TLE while lateral temporal hyperperfusion 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 hyperperfusion in the neighboring brain regions where ictal discharges propagated. Conclusion: Hypoperfusion as well as hyperperfusion in ictal SPECT should be considered for localizing epileptic focus. Although the mechanism of ictal hypoperfusion 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.

• The Korean Journal of Nuclear Medicine
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• v.33 no.3
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• pp.262-272
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• 1999

Purpose: Interictal F-18-fluorodeoxyglucose (FDG) PET and ictal Tc-99m-HMPAO SPECT are found to be useful in localizing epileptogenic zones in neocortical lateral temporal or frontal lobe epilepsy. We investigated whether interictal F-18-FDG PET or ictal Tc-99m-HMPAO SPECT was useful to find epileptogenic Bones in occipital lobe epilepsy (OLE). Materials and Methods: We reviewed patterns of hypometabolism in interictal F-18-FDG PET and of hyperperfusion in ictal Tc-99m-HMPAO SPECT in 17 OLE patients (mean age=$27{\pm}6.8$ year, M:F= 10:7, injection time= $30{\pm}17$ sec). OLE was diagnosed based on invasive electroencephalography (EEG) study, surgery and post-surgical outcome (Engel class I in all for average 14 months). Results: Epileptogenic zones were correctly localized in 9 (60%) out of 15 patients by interictal F-18-FDG PET. Epiletogenic hemispheres were correctly lateralized in 14 patients (93%). By ictal Tc-99m-HMPAO SPECT, epileptogenic hemispheres were correctly lateralized in 13 patients (76%), but localization was possible only in 3 patients (18%). Among patients who showed no abnormality with MR imaging and no correct localization with ictal Tc-99m-HMPAO SPECT, interictal F-18-FDG PET was helpful in 2 patients. Conclusion: Ictal Tc-99m-HMPAO SPECT was helpful in lateralization but not in localization in OLE. Interictal F-18-FDG PET was helpful for localization of epileptogenic zones even in patients with ambiguous MR or ictal SPECT findings.

• Annals of Clinical Neurophysiology
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• v.1 no.2
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• pp.112-117
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• 1999

Background : Posterior tibial nerve somatosensory evoked potentials (PTSEP) have cortical potentials on primary sensory area of foot around 40 msec. The direct cortical recordings of the cortical potentials shows high voltage positive wave on medial hemisphere, especially on paracentral lobule (PCL). However, it is so difficult to record the potential directly on PCL that the cortical potential of PTSEP is not well understood. We investigated the cortical potential of PTSEP on subdural electrodes. Methods : We recorded cortical potentials to posterior tibial nerve stimulation on subdural electrodes which were on medial hemisphere near PCL in 15 intractable neocortical epilepsy patients. The numbers of subdural electrodes were 8 in 10 subjects ($1{\times}8array$) and 16 in 5 subjects ($2{\times}8arrays$). Seven subjects had three-dimensional imaging fusion (3D-fusion) of MRI and the electrodes using Analyze program. We investigated the amplitude, latency, polarity, and phase of the waves regarding location. Results : The waves had maximal amplitude on PCL in 4 subjects, precuneus in 1, cingulate gyrus nearest to PCL in 2 among 7 subjects with 3D-fusion. Also the electrodes were located on posterior area of PCL (2 out of 2 subjects with more than two electrodes put on PCL in 3D-fusion) and superior area of it (5 out of 5 subjects with $2{\times}8arrays $). All the high (more than 20 uV) amplitude around 40msec had positive polarity in 7 subjects. The phase reversals were detected between the electrodes with the highest amplitude and the just posterior (2 subjects) or anterior (6 subjects) located electrodes. The just posterior located electrodes had sharper phase reversal than the anterior one. Conclusion : PTSEP might have maximal amplitude of cortical potentials on the more superior and posterior area of PCL. The highest amplitude potential has positivity. The wave with maximal amplitude could have phase reversal of cortical potentials with surrounding electrodes, especially shaper with posterior part than with anterior one.