Stereo-electroencephalography methodology: advantages and limits (original) (raw)
Related papers
Neurosurgery, 2005
To report on indications, surgical technique, results, and morbidity of stereoelectroencephalography (SEEG) in the presurgical evaluation of patients with drug-resistant focal epilepsy. METHODS: Two-hundred fifteen stereotactic implantations of multilead intracerebral electrodes were performed in 211 patients (4 patients were explored twice), who showed variable patterns of localizing incoherence among electrical (interictal/ictal scalp electroencephalography), clinical (ictal semeiology), and anatomic (magnetic resonance imaging [MRI]) investigations. MRI scanning showed a lesion in 134 patients (63%; associated with mesial temporal sclerosis in 7) and no lesion in 77 patients (37%; with mesial temporal sclerosis in 14 patients). A total of 2666 electrodes (mean, 12.4 per patient) were implanted (unilaterally in 175 procedures and bilaterally in 40). For electrode targeting, stereotactic stereoscopic cerebral angiograms were used in all patients, coupled with a coregistered three-dimensional MRI scan in 108 patients. RESULTS: One hundred eighty-three patients (87%) were scheduled for resective surgery after SEEG recording, and 174 have undergone surgery thus far. Resections sites were temporal in 47 patients (27%), frontal in 55 patients (31.6%), parietal in 14 patients (8%), occipital in one patient (0.6%), rolandic in one patient (0.6%), and multilobar in 56 patients (32.2%). Outcome on seizures (Engel's classification) in 165 patients with a follow-up period of more than 12 months was: Class I, 56.4%; Class II, 15.1%; Class III, 10.9%; and Class IV, 17.6%. Outcome was significantly associated with the results of MRI scanning (P ϭ 0.0001) and with completeness of lesion removal (P ϭ 0.038). Morbidity related to electrode implantation occurred in 12 procedures (5.6%), with severe permanent deficits from intracerebral hemorrhage in 2 (1%) patients. CONCLUSION: SEEG is a useful and relatively safe tool in the evaluation of surgical candidates when noninvasive investigations fail to localize the epileptogenic zone. SEEG-based resective surgery may provide excellent results in particularly complex drug-resistant epilepsies.
Clinical Ictal Symptomatology and Anatomical Lesions: Their Relationships in Severe Partial Epilepsy
Epilepsia, 2007
High-resolution imaging techniques can demonstrate anatomic alterations in most patients identified as candidates for surgical treatment of their partial epilepsy. The demonstration of an anatomic lesion is only one step in the presurgical diagnostic procedure, which includes video-EEG and, when necessary, video-stereo-EEG recordings of seizures. A review of the literature shows that the simple removal of the magnetic resonance imaging (MR1)-evident lesion ("lesionectomy") reduces but does not completely suppress seizures in a large percentage of patients, especially those with neuronal migration disorders. This phenomenon could, at least in part, be explained by preliminary data (in 33 patients) showing that less than 20% of seizures correspond to a well-localized, intralesional discharge in about 40% of stereo-EEG-investigated patients with at least one intralesional electrode. The authors illustrate some anatomo-electroclinical examples of intraindividual variability of the ictal symptomatology, raising the problem of the decision about the extent of the surgical removal. Recent histologic and immunohistochemical studies have demonstrated several kinds of structural alterations in the stereo-EEG-defined epileptogenic zone, not always overlapping with the MRI-visible lesion. This aspect can further explain some failures of MRI-guided lesionectomies. That relationships between "lesions" and epileptogenic zones may be variable is also suggested by reports of patients who present with multiple lesions (i.e., cavernous angiomas, Bourneville syndrome) and are cured by removal of only one of them. Key Words: Severe partial epilepsy-Epileptogenic lesions-Stereo-EEG-Intralesional electrical activity-Epilepsy surgery.
Seminar in Epileptology Concept of epilepsy surgery and presurgical evaluation
Epilepsy surgery is a well-accepted treatment for drug-resistant epilepsy. The success of the epilepsy surgery depends upon an appropriate presurgical evaluation process which should ensure the selection of suitable patients who are likely to become seizure-free following surgery without any unacceptable deficit. The two basic goals of the presurgical evaluation are the accurate localization and delineation of the extent of the epileptogenic zone, and its complete and safe resection. The process of the presurgical evaluation requires a multimodality approach wherein each modality provides unique and complimentary information which is combined with the information provided by other modalities to generate a hypothesis with regard to the likely epileptogenic zone. The basic modalities for the presurgical evaluation are clinical history, long-term video-EEG recording, high-resolution MRI, and neuropsychological evaluation. The additional modalities include functional imaging studies, electrical and magnetic source imaging, functional MRI, and intracranial monitoring. Each modality has its own limitations and the information provided by none of them is absolute. Hence, a concordance among the different modalities is the key to surgical success. The presurgical evaluation is a step-wise process starting form the most basic and most reliable tests and progressing to more complex and invasive modalities. The number of tests required varies according to the complexity involved and may include very basic minimum investigations in a given case, to the use of all the available investigations in more complex cases. The proper selection of various investigations and their accurate interpretation at each stage is required to ensure a successful outcome. In this article, we intend to review some of these basic concepts of presurgical evaluation and epilepsy surgery, and try to provide a frame work of the presurgical evaluation process.
Presurgical evaluation of epilepsy patients
Medicina, 2008
Epilepsy surgery has been established as an effective treatment in pharmacoresistant focal epilepsies. Most candidates for epilepsy surgery are patients with partial epilepsy syndromes refractory to medical treatment. The curative surgery procedure is resection of the epileptogenic zone; therefore, precise detection of the site responsible for seizure generation is necessary. Modern structural and functional imaging techniques have made presurgical evaluation less invasive and available for a higher number of patients. Video electroencephalography (EEG) monitoring, high-resolution structural and functional imaging techniques are used widely for presurgical evaluation. When noninvasive evaluation is not sufficient for the detection of the epileptogenic zone, invasive EEG monitoring and intracarotid amobarbital test are used. A classical example of a surgically curable epilepsy syndrome is mesial temporal lobe epilepsy with about 70–80% of patients becoming free of seizures after surg...
Stereoelectroencephalography in presurgical assessment of MRI-negative epilepsy
Brain, 2007
According to most existing literature, the absence of an MRI lesion is generally associated with poorer prognosis in resective epilepsy surgery. Delineation of the epileptogenic zone (EZ) by intracranial recording is usually required but is perceived to be more difficult in 'MRI negative' cases. Most previous studies have used subdural recording and there is relatively less published data on stereoelectroencephalography (SEEG). The objective of this study was to report the experience of our group in using SEEG in presurgical evaluation, comparing its effectiveness in normal and lesional MRI cases. One hundred consecutive patients undergoing SEEG for presurgical assessment were studied. Forty-three patients out of one hundred (43%) had normal MRI and 57 (57%) had lesional MRI. Successful localization was achieved with no difference between these two groups, in 41/43 (95%) normal MRI and in 55/57 (96%) lesional MRI cases (P = 1.00). Surgery was proposed in 84/100 patients and contraindicated in 16/100 with no significant difference between lesional and MRI-negative groups (P`0.05). At 1 year follow-up, 11/20 (55%) of those having undergone cortectomy in the MRI-negative group and 21/40 (53%) in the lesional MRI group were entirely seizure free (P`0.05) and these proportions were maintained at 2 years follow-up. Significant improvement in seizure control (ILAE outcome groups 1^4) was achieved in`90% cases with no difference between groups (P`0.05). Of MRI-negative cases that underwent surgery, 10/23 (43%) had focal cortical dysplasia. This series showed that SEEG was equally effective in the presurgical evaluation of MRInegative and lesional epilepsies.
Surgical Outcome of Epilepsy Patients Evaluated with a Noninvasive Protocol
Epilepsia, 2000
Surgery is now an accepted treatment for some medically intractable epilepsies. Presurgical evaluation is particularly important for the localization of the epileptogenic zone, which may necessitate sophisticated imaging techniques and intracranial electroencephalogram (EEG) recordings. If patients are carefully selected, however, successful results can be achieved with noninvasive evaluation methods. Seventy-seven patients were operated on for intractable seizures. All patients underwent EEG, neuropsychological, psychiatric, and magnetic resonance imaging investigations. Ictal EEG-video recording was performed in all nonlesional and in some lesional cases that had discordant data. Selective amygdalo-hippocampectomy was performed on patients with mesial temporal lobe epilepsy (MTLE), an extended or a limited lesionectomy was performed on patients with structural lesions, and a lesionectomy with deafferentation was performed on two patients with West syndrome. Electrocorticography was not used. Tem-
Epilepsy surgery: perioperative investigations of intractable epilepsy
Anatomy and Embryology, 2005
Recent advances in our understanding of the basic mechanisms of epilepsy have derived, to a large extent, from increasing ability to carry out detailed studies on patients surgically treated for intractable epilepsy. Clinical and experimental perioperative studies divide into three different phases: before the surgical intervention (preoperative studies), on the intervention itself (intraoperative studies), and on the period when the part of the brain that has to be removed is available for further investigations (postoperative studies). Before surgery, both structural and functional neuroimaging techniques, in addition to their diagnostic roles, could be used to investigate the pathophysiological mechanisms of seizure attacks in epileptic patients. During epilepsy surgery, it is possible to insert microdialysis catheters and electroencephalogram electrodes into the brain tissues in order to measure constituents of extracellular fluid and record the bioelectrical activity. Subsequent surgical resection provides tissue that can be used for electrophysiological, morphological, and molecular biological investigations. To take full advantage of these opportunities, carefully designed experimental protocols are necessary to compare the data from different phases and characterize abnormalities in the human epileptic brain.
Concept of epilepsy surgery and presurgical evaluation
Epileptic disorders : international epilepsy journal with videotape, 2015
Epilepsy surgery is a well-accepted treatment for drug-resistant epilepsy. The success of the epilepsy surgery depends upon an appropriate presurgical evaluation process which should ensure the selection of suitable patients who are likely to become seizure-free following surgery without any unacceptable deficit. The two basic goals of the presurgical evaluation are the accurate localization and delineation of the extent of the epileptogenic zone, and its complete and safe resection. The process of the presurgical evaluation requires a multimodality approach wherein each modality provides unique and complimentary information which is combined with the information provided by other modalities to generate a hypothesis with regard to the likely epileptogenic zone. The basic modalities for the presurgical evaluation are clinical history, long-term video-EEG recording, high-resolution MRI, and neuropsychological evaluation. The additional modalities include functional imaging studies, el...