FDG-PET Cerebral Imaging In Surgical Decision Making Of Refractory Epilepsy

Background and Objectives:Epilepsy is a chronic central nervous system disease, the prevalence is about5‰in China. Most of the patients can get remission through antiepileptic drug thrapy, but still20%of the patients are intractable. For many of these patients epilepsy surgery offers the only opportunity to become free of seizures. If definite epileptogenic zone can be located, most patients will get seizure free or reduction after resection. So accurate preoperative locating is very important for epilepsy surgery. Most of the patients undergo a variety of noninvasive preoperative examinations in order to locate the epileptic zone, and evaluate the eligibility for operation. Advances in technology to localize focal epileptogenic zone, such as high resolution magnetic resonance imaging (MRI), have substantially improved the success of surgical treatment. As some patients are difficult to locate with non-invasive methods, invasive electrophysiological examinations are needed. As invasive electrophysiological examinations are expensive, also have risk of complications, the application needs sufficient supporting evidences.18-fluorodeoxyglucose positron emission tomography (FDG-PET) has been widely used in epilepsy epileptogenic zone localization since the1980s. The sensitivity and accuracy has been confirmed by lots of researches. FDG-PET can be used to judge whether the patient be appropriate for surgery, and forecast the surgical outcome. For some patients hard to locate epileptic zones, FDG-PET images can also be used to support the application of invasive electrophysiological examinations, provide information directing the planting of intracranial electrodes. We discussed the directive value of FDG-PET in the surgical decision making of refractory epilepsy.Methods and Materials:We retrospectively reviewed164refractory epilepsy cases(91M,73F) of Peking Union Medical College Hospital admitted from January2006to April2011with an average age of26.1y. The course of disease distribute form1to44y with an average of12.8y. All of them underwent interictal FDG-PET examination. We collected the results of FDG-PET, scalp video monitoring electroencephalogram(SVEEG), brain MRI, preoperative intracranial electroencephalogram(ICEEG), intraoperative electrocorticogram(ECoG) and the details of operation, evaluated the surgical outcome through telephone follow-up and outpatient medical records with the International League Against Epilepsy(ILAE)2001surgical outcome classification. We compared the localization rates of FDG-PET, SVEEG, and MRI for epileptogenic zone, checked the directive value of FDG-PET in the decision making and planting of invasive examinations. Relationship between the cerebral FDG metabolic pattern and surgical outcome were also evaluated.Results and Discussions:1.104patients got good surgical outcome.101of them had concordant epileptic zone located by FDG-PET. The sensitivity of FDG-PET in epileptic zone locating is97.1%, higher than MRI(83.7%,P=0.002) and SVEEG(85.6%, P=0.002). FDG-PET also successfully located the epileptic zone in all5cases of frontal lobe epilepsy and13cases of MRI-negative temporal lobe epilepsy. Metabolic abnormalities could be found in10of12posterior cortical epilepsy(PCE) cases by FDG-PET.2.8cases with multiple lobe hypometabolic foci got poor surgical outcome. Other18patients with multiple lobe hypometabolic foci were excluded from surgery. In temporal lobe epilepsy with single focal hypometabolic focus, diaschisis such as ipsilateral thalamus and cerebella metabolic changes can be used as a predictive factor of poor surgical outcome, the odds ratio(OR) is7.73(P=0.003,95%CI:1.96,30.52), as the image that hypometabolic zone spreading over extratemporal cortex also has an OR of32.54(P<0.001,95%CI:6.40,165.44). FDG-PET can be used to predict the surgical outcome and exclude patients, change the surgical decision.3. Discharges were found in25patients underwent ICEEG. The locating results of ICEEG were concordant with FDG-PET results in19of patients.10of11extratemporal epilepsy patients had concordant result of ICEEG. FDG-PET can provide sufficient information for the presurgical planning and planting of electrodes.5patients with focal temporal lobe hypometabolic zone and concordant MRI results showed consistency between ICEEG and FDG-PET. In those MRI-positive with FDG-PET-positive TLE patients, the application of ICEEG should be reevaluated. 4. Discharges were found in74of75patients underwent ECoG.74patients had concordant results between FDG-PET and ECoG. In those TLE patients underwent anterior temporal lobectomy and selective amygdalohippocampectomy, ECoG is not more informative than FDG-PET. In the patients of FLE and PCE, ECoG is still important for delineate the epilepsy foci, so FDG-PET can provide information in planning and planting of electrode as the high concordance between FDG-PET and ECoG.Conclusion:FDG-PET can be used to evaluate the eligibility and support surgical decision for the sufficient sensitivity and accuracy in localizing the seizure focus. As the patterns of the FDG-PET metabolic image are related with surgical outcome, FDG-PET can be used to exclude patients, reducing poor surgical outcomes. FDG-PET can also provide information for the prognostic planning and planting of invasive EEG examination. We conclude that FDG-PET has directive value in the surgical decision making of epilepsy.