Epidural and foramen-ovale electrodes in the diagnostic evaluation of patients considered for epilepsy surgery (original) (raw)
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Foramen ovale electrodes in the evaluation of epilepsy surgery: Conventional and unconventional uses
Epilepsy & Behavior, 2011
Foramen ovale (FO) electrodes have been used in the evaluation of epilepsy surgery for more than 25 years. Their traditional application was in patients with mesial temporal lobe epilepsy. Due in part to advances in neuroimaging, their use has declined. We describe our cumulative experience with FO electrodes and use examples to illustrate a range of indications for FO recordings that extend beyond their conventional utility for mesial temporal lobe cases. We also summarize the pros and cons of FO electrodes implantation and attempt to reestablish their utility in presurgical evaluation.
Invasive epilepsy surgery evaluation
Seizure, 2017
Intracranial EEG (iEEG) recordings are widely used for the work up of pharmacoresistant epilepsy. Different iEEG recording techniques namely subdural grids, strips, depth electrodes and stereoencephalography (SEEG) are available with distinct limitations and advantages. Epilepsy centres mastering multiple techniques apply them in an individualised patient approach. These tools are used to map the seizure onset zone which is pivotal in approximating the epileptogenic zone, i.e. the zone which is indispensable for the generation of seizures and when resected will render the patient seizure free. Besides, the implanted electrodes can be used to define eloquent cortex through direct cortical stimulation. Different clinical scenarios exist which favour one iEEG recording technique over the other. Proximity of the presumed epileptogenic zone to eloquent cortex, for example, is a clinical scenario which may favour grid electrodes over SEEG. We here review the indication for iEEG for the work-up of patients suffering from pharmacoresistant epilepsy. In addition, we provide a description of the recording techniques focussing on the main techniques used: grid electrodes, depth electrodes and stereoencephalography. We then outline different clinical scenarios and the preferred technical approach for intracranial recordings in these scenarios. Finally, we highlight which advances have been made in the field of iEEG and which advances are in the pipeline waiting to be established for clinical use. This review provides the clinician with an update on the diagnostic use of intracranial EEG for epilepsy surgery and thus aids in understanding patient selection for this technique which may ultimately improve referral patterns.
Electrocorticographic Patterns in Epilepsy Surgery and Long-Term Outcome
Journal of Clinical Neurophysiology, 2017
The role of intraoperative electrocorticography (iECoG) and of its patterns in epilepsy surgery have shown contradictory results. Our aim was to describe iECoG patterns and their association with outcome in epilepsy surgery. Methods: We retrospectively analyzed 104 patients who underwent epilepsy surgery (2009-2015) with pre-and postresection iECoG. We described clinical findings, type of surgery, preresection iECoG patterns according to Palmini et al., 1995 (sporadic, continuous, burst, and recruiting interictal epileptiform dischargesdIEDs) and postresection iECoG outcome (de novo, residual, and without IEDs). The Engel scale was used to evaluate the outcome. Descriptive statistics, Kaplan-Meier, the logistic regression model, and analysis of variance tests were used. Results: We included 60.6% (63/104) females, with a mean age of 35 (610.2) years at the time of epilepsy surgery. The etiologies were hippocampal sclerosis (63.5%), cavernomas (14.4%), cortical dysplasia (11.5%), and low-grade tumors (10.6%). The most common preresection iECoG pattern was sporadic IEDs (47%). Postresection iECoG patterns were de novo (55.7%), residual (27.8%), and without IEDs (16.3%). Mean follow-up was 19.2 months. Engel scale was as follows: Engel I (91 patients, 87.5%), Engel II (10 patients, 9.6%), and Engel III (three patients, 2.9%). Analysis by mixed-design analysis of variance showed a significant difference between etiology groups with a strong size effect (P ¼ 0.021, h 2 ¼ 0.513) and also between preresection iECoG patterns (P ¼ 0.008, h 2 ¼ 0.661). Conclusions: Preresection iECoG patterns and etiology influence Engel scale outcome in lesional epilepsy surgery.
Morbidity Associated With the Use of Intracranial Electrodes for Epilepsy Surgery
The Canadian Journal of Neurological Sciences, 2006
ABSTRACT:Background:Invasive monitoring for the investigation of medically intractable epilepsy may be associated with undesirable morbidity. We performed a review of our recent experience to determine the incidence of major complications.Methods:We reviewed the clinical records of all patients who underwent invasive EEG monitoring at our institution between 2000 and 2004.Results:One-hundred and sixteen patients (57 males, 59 females) with a mean age of 32 years of age underwent intracranial placement of electrodes for epilepsy surgery investigation. Subdural strips were placed in 115 patients with a mean of eight strips per patient. Subdural grids were inserted in 11 patients and depth electrodes in five. Fourteen of the 15 patients with grids or depth electrodes also had strips. Coverage was unilateral in 37 patients and bilateral in 79 patients. Electrodes were placed over the frontal lobe in 78 cases, temporal in 93, parietal in 24, and occipital in 27 patients. The average dura...
Epilepsia, 2016
Intracranial monitoring is fundamental to epilepsy surgery, with reported complication rates of 3-17%. We aimed to assess the differences in complication rates between subdural and depth electrodes. We conducted a retrospective review of 317 electrode implantation procedures. All documented abnormal postoperative findings were recorded in our study. Those that resulted in a significant alteration of treatment course, including neurologic deficit, long-term medication use, reoperation, or hospital readmission, were deemed clinically significant. When possible, findings were attributed to a particular electrode type based on relative location to each electrode. Postoperative abnormalities were associated with SDE placement in 152 (47.9%) procedures and 40 (25.2%) DE placements (p < 0.001). Twenty-nine (9.1%) clinically significant complications were seen in the subdural electrode (SDE) group compared to 10 associated with DEs (6.3%, p = 0.37). SDEs were associated with increased ra...
Epilepsia, 2006
Summary: Purpose: We analyze a series of patients with mesial temporal lobe epilepsy (MTLE) associated with hippocampal sclerosis (HS) submitted to presurgical investigation with scalp sphenoidal, followed by foramen ovale electrodes (FO), and, when necessary, with depth temporal electrodes. We sought to evaluate the clinical utility of FO in patients with MTLE-HS.Methods: We included patients who had phase I investigation with bitemporal independent seizures, nonlateralized ictal onsets, or ictal onset initiating in the side contralateral to the side of hippocampal sclerosis. Patients whose implanted FO failed to demonstrate an unambiguous unilateral ictal onset were later evaluated with depth hippocampal electrodes.Results: Between May 1994 and December 2004, 64 patients met our inclusion criteria: 33 female (51.5%) and 31 male subjects (48.5%). The mean age at enrollment was 37.66 ± 10.6 years (range, 12–56 years). The groups with nonlateralized surface ictal EEG onsets and contralateral EEG onsets had a greater chance of lateralization with FO when compared with the group with bilateral independent seizures on surface EEG (p < 0.01). Foramen ovale electrodes lateralized the seizures in 60% of patients. Seventy percent of patients became seizure free after temporal lobectomy. Five patients were implanted with depth temporal electrodes after FO video-EEG monitoring. The depth-electrode EEG onsets confirmed the results of FO video-EEG monitoring in all patients, and the surgery was refused.Conclusions: In MTLE-HS, FO is a reliable method for lateralization of seizures that are not clearly recorded by surface EEGs.
Subdural and depth electrodes in the presurgical evaluation of epilepsy
Acta Neurochirurgica, 1994
From 1987 to 1992, invasive EEG studies using subdural strips, grids or depth electrodes were performed in a total of 160 patients with medically intractable epilepsy, in whom scalp EEG was insufficient to localize the epileptogenic focus. Dependent on the individual requirements, these different electrode types were used alone or in combination. Multiple strip electrodes with 4 to 16 contacts were implanted in 157 cases through burrholes, grids with up to 64 contacts in 15 cases via boneflaps, and intrahippocampal depth electrodes in 36 cases using stereotactic procedures. In every case, localization of the electrodes with respect to brain structures was controlled by CT scan and MRI. Visual and computerized analysis of extra-operative recordings allowed the localization of a resectable epileptogenic focus in 143 patients (89%), who subsequently were referred for surgery, whereas surgery had to be denied to 17 patients (11%). We did not encounter any permanent morbidity or mortality in our series. In our experience, EEG-mouitoring with chronically implanted electrodes is a feasible technique which contributes essentially to the exact localization of the epileptogenic focus, since it allows nearly artefact-free recording of the ictal and interictal activity. Moreover, grid electrodes can be used for extra-operative functional topographic mapping of eloquent brain areas.
Acta Neurochirurgica, 2009
Background Intracranial electrode monitoring is still required in epilepsy surgery; however, it is associated with significant morbidity. Objective To identify risk factors associated with complications during invasive intracranial EEG monitoring. Materials and methods Retrospective study of all patients undergoing invasive monitoring at Westmead between 1988-2004. From detailed chart reviews, the following variables were recorded: duration of intracranial monitoring, the site of grid implantation, number of grids and electrodes, seizure frequency, postoperative complications and seizure outcome. Results Seventy-one patients (median age: 24 years) underwent subdural electrode implantation; 62% had extratemporal lobe epilepsy and 46% were non-lesional. Of the 58 monitored patients who had cortical resections, 45 had good seizure outcomes. Complications related to subdural electrode implantation included transient complications requiring no treatment (12.7%), transient complications requiring treatment (9.9%) and two deaths (2.8%). Specific complications included subdural haemorrhage, transient neurological deficit, infarction and osteomyelitis. The two deaths occurred within 48 h of implantation were related to raised intracranial pressure (one venous infarction, one unexplained). Complications were associated with maximal size of grid (p<0.001), greater number of electrodes (p<0.001), electrode density per cortical surface implanted (p<0.001), right central surface implantation (p=0.003) and left central surface implantation (p=0.013). Multiple logistic regression identified larger size grids and right central surface implantation as independent predictors of complications. Conclusion There are significant complications during intracranial EEG evaluations but the majority of these are transient. We found a relationship between the size of the electrode arrays and the incidence of complications. The results of this study have been used to modify our implantation and monitoring protocols.
Turkish Neurosurgery, 2010
AIM: This paper aimed to provide information related to surgical and neurological complications encountered following intracranial electrode placements in patients with medically intractable epilepsy. MATERIAL and METHODS: Retrospective review of 70 patients with either subdural grid/strip or depth electrode implanted between 2004 and 2009 at the Epilepsy Unit in Cerrahpasa Medical Faculty. RESULTS: A total of 276 electrode implantations were performed in 70 patients. There were no deaths related to implantation. The occurrence of infection and intracranial hematoma were found to be 1.4 and 1.4%, respectively. A total of 1 patient (1.4%) showed transient neurological complications. The rate of overall morbidity including neurological complications was found to be 4.2% (n = 3). CONCLUSION: Based on our experience, intracranial electrode implantation is an effective and safe method with extremely low morbidity rate, especially in experienced hands.