The 3-Dimensional Grid

Abstract BACKGROUND Successful surgical treatment of epilepsy requires accurate definition of areas of ictal onset and eloquent brain. Although invasive monitoring can help, subdural grids cannot sample sulci or subcortical tissue; traditional stereoelectroencephalography depth electrodes are usually placed too far apart to provide sufficient resolution for mapping. OBJECTIVE To report a strategy of depth electrode placement in a dense array to allow precise anatomic localization of epileptic and eloquent cortex. METHODS Twenty patients with medically intractable epilepsy either poorly localized or found to arise adjacent to eloquent areas underwent placement of arrays of depth electrodes into and around the putative area of seizure onset with the use of framed stereotaxy. Each array consisted of a “grid” of parallel electrodes in a rectangular pattern with 1 cm between entry sites. In a subset of patients, a few electrodes were placed initially, with additional electrodes placed in a second stage. Trajectories were modified to avoid cortical vessels defined on magnetic resonance imaging. Patients were monitored for 4 to 21 days to establish the precise location of seizure onset. Stimulation was performed to map cortical and subcortical eloquent regions. Electrode locations were coregistered for frameless stereotaxy during subsequent resection of seizure focus. RESULTS Two hundred fifty-four electrodes were implanted. Discrete regions of seizure onset and functional cortex were identified, which were used during resection to remove epileptogenic tissue while preserving eloquent areas. There were no hemorrhagic or infectious complications; no patient suffered permanent neurological deficit. CONCLUSION The 3-dimensional intraparenchymal grid is useful for identifying the location and extent of epileptic and eloquent brain.

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Freehand placement of depth electrodes using electromagnetic frameless stereotactic guidance

Journal of Neurosurgery Pediatrics ◽

10.3171/2011.8.peds11143 ◽

2011 ◽

Vol 8 (5) ◽

pp. 464-467 ◽

Cited By ~ 8

Author(s):

Carter D. Wray ◽

Diana L. Kraemer ◽

Tong Yang ◽

Sandra L. Poliachik ◽

Andrew L. Ko ◽

...

Keyword(s):

Electrode Placement ◽

Frameless Stereotaxy ◽

Seizure Onset ◽

Presurgical Evaluation ◽

Electromagnetic System ◽

Depth Electrodes ◽

Depth Electrode ◽

Stereotactic Frame ◽

Stereotactic Guidance ◽

Patients With Epilepsy

The presurgical evaluation of patients with epilepsy often requires an intracranial study in which both subdural grid electrodes and depth electrodes are needed. Performing a craniotomy for grid placement with a stereotactic frame in place can be problematic, especially in young children, leading some surgeons to consider frameless stereotaxy for such surgery. The authors report on the use of a system that uses electromagnetic impulses to track the tip of the depth electrode. Ten pediatric patients with medically refractory focal lobar epilepsy required placement of both subdural grid and intraparenchymal depth electrodes to map seizure onset. Presurgical frameless stereotaxic targeting was performed using a commercially available electromagnetic image-guided system. Freehand depth electrode placement was then performed with intraoperative guidance using an electromagnetic system that provided imaging of the tip of the electrode, something that has not been possible using visually or sonically based systems. Accuracy of placement of depth electrodes within the deep structures of interest was confirmed postoperatively using CT and CT/MR imaging fusion. Depth electrodes were appropriately placed in all patients. Electromagnetic-tracking–based stereotactic targeting improves the accuracy of freehand placement of depth electrodes in patients with medically refractory epilepsy. The ability to track the electrode tip, rather than the electrode tail, is a major feature that enhances accuracy. Additional advantages of electromagnetic frameless guidance are discussed.

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Robotic image-guided depth electrode implantation in the evaluation of medically intractable epilepsy

Neurosurgical FOCUS ◽

10.3171/foc/2008/25/9/e19 ◽

2008 ◽

Vol 25 (3) ◽

pp. E19 ◽

Cited By ~ 19

Author(s):

William J. Spire ◽

Barbara C. Jobst ◽

Vijay M. Thadani ◽

Peter D. Williamson ◽

Terrance M. Darcey ◽

...

Keyword(s):

Intractable Epilepsy ◽

Robotic System ◽

Electrode Placement ◽

Seizure Onset ◽

Electrode Implantation ◽

Grid Electrode ◽

Image Guided ◽

Depth Electrodes ◽

Depth Electrode ◽

Time Period

Object The authors describe their experience with a technique for robotic implantation of depth electrodes in patients concurrently undergoing craniotomy and placement of subdural monitoring electrodes for the evaluation of intractable epilepsy. Methods Patients included in this study underwent evaluation in the Dartmouth Surgical Epilepsy Program and were recommended for invasive seizure monitoring with depth electrodes between 2006 and the present. In all cases an image-guided robotic system was used during craniotomy for concurrent subdural grid electrode placement. A total of 7 electrodes were placed in 4 patients within the time period. Results Three of 4 patients had successful localization of seizure onset, and 2 underwent subsequent resection. Of the patients who underwent resection, 1 is now seizure free, and the second has only auras. There was 1 complication after subpial grid placement but no complications related to the depth electrodes. Conclusions Robotic image-guided placement of depth electrodes with concurrent craniotomy is feasible, and the technique is safe, accurate, and efficient.

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Depth Electrodes: Approaches and Complications

Invasive Studies of the Human Epileptic Brain ◽

10.1093/med/9780198714668.003.0005 ◽

2018 ◽

pp. 50-62

Author(s):

Thomas Ostergard ◽

Jonathan P. Miller

Keyword(s):

Intracranial Haemorrhage ◽

Electrode Placement ◽

Frameless Stereotaxy ◽

Electrode Implantation ◽

Depth Electrodes ◽

Stereotactic Frame ◽

Electrode Length ◽

Using Data ◽

Intracranial Electrode ◽

Neurosurgical Operation

Depth electrode placement is an invaluable technique in treating patients with refractory epilepsy. Like any neurosurgical operation, planning is the most important phase of the procedure. The seizure focus should first be grossly localized using data from scalp electrodes and seizure semiology. This gross localization will guide placement of invasive electrophysiological hardware. All electrode implantation methods rely on Talairach’s principles of stereotaxis. Traditional electrode implantation is performed with a stereotactic frame. Evolving techniques use frameless stereotaxy or neuroendoscopy for implantation. The most worrisome complication of electrode placement is electrode-associated intracranial haemorrhage. Electrode deviation is a much more common complication, which can be minimized by avoiding extreme insertion angles, minimizing intracranial electrode length, and maximizing entry point accuracy.

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Bilateral Intracranial Electrodes for Lateralizing Intractable Epilepsy

Neurosurgery ◽

10.1227/01.neu.0000363184.43723.94 ◽

2010 ◽

Vol 66 (2) ◽

pp. 274-283 ◽

Cited By ~ 42

Author(s):

Dimitris G. Placantonakis ◽

Saadat Shariff ◽

Fabien Lafaille ◽

Douglas Labar ◽

Cynthia Harden ◽

...

Keyword(s):

Surgical Complication ◽

Intractable Epilepsy ◽

Electrode Placement ◽

Wada Test ◽

Interictal Spikes ◽

Curative Surgery ◽

Depth Electrodes ◽

Intracranial Electrode ◽

Intracranial Electrodes ◽

Video Eeg

Abstract OBJECTIVE Medically refractory epilepsy is amenable to neurosurgical intervention if the epileptogenic focus is accurately localized. If the scalp video-electroencephalography (EEG) and magnetic resonance imaging are nonlateralizing, yet a single focus is suspected, video-EEG monitoring with bilateral intracranial electrode placement is helpful to lateralize the ictal onset zone. We describe the indications, risks, and utility of such bilateral surveys at our institution. METHODS We retrospectively reviewed 26 patients with medically refractory seizures who were treated over a 5-year period and underwent bilateral placement of intracranial electrodes. Subdural strips were used in all cases, and additional stereotactic implantation of depth electrodes into mesial temporal lobes occurred in 50%. The mean patient age was 37.7 years, and 65.4% of patients were male. RESULTS The most common indication for bilateral invasive monitoring was bilateral ictal onsets on surface video-EEG (76.9%), followed by frequent interictal spikes contralateral to a single ictal focus (7.7%). Intracranial monitoring lasted an average of 8.2 days, with ictal events recorded in all cases. Ten patients (38.5%) subsequently underwent more extensive unilateral monitoring via implantation of subdural and depth electrodes through a craniotomy. A therapeutic procedure was performed in 17 patients (65.4%), whereas 1 patient underwent a palliative corpus callosotomy (3.8%). Nine patients underwent a resection without unilateral invasive mapping. Reasons for no therapeutic surgery (n = 8) included multifocal onsets, failing the Wada test, refusal of further treatment, and negative intraoperative electrocorticogram. There was 1 surgical complication, involving a retained electrode fragment that was removed in a separate minor procedure. Of the 26 patients, 15 (57.7%) are now seizure-free or have seizure disorders that have substantially improved (modified Engel classes I and II). Of the 17 patients who underwent a potentially curative surgery, 13 (76.5%) were Engel classes I and II. CONCLUSION Bilateral placement of subdural strip and depth electrodes for epilepsy monitoring in patients with nonlateralizing scalp EEG and/or discordant imaging studies but clinical suspicion for focal seizure origin is both safe and effective. Given the safety and efficacy of this procedure, epileptologists should have a low threshold to consider bilateral implants for suitable patients.

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Utility and safety of depth electrodes within the supratemporal plane for intracranial EEG

Journal of Neurosurgery ◽

10.3171/2018.4.jns171812 ◽

2019 ◽

Vol 131 (3) ◽

pp. 772-780 ◽

Cited By ~ 3

Author(s):

Yasunori Nagahama ◽

Alan J. Schmitt ◽

Brian J. Dlouhy ◽

Adam S. Vesole ◽

Phillip E. Gander ◽

...

Keyword(s):

Temporal Lobe ◽

Clinical Information ◽

Epileptic Activity ◽

Temporal Lobectomy ◽

Electrode Placement ◽

Seizure Freedom ◽

Seizure Onset ◽

Prognostic Information ◽

Depth Electrodes ◽

Electrode Coverage

OBJECTIVEThe epileptogenic zones in some patients with temporal lobe epilepsy (TLE) involve regions outside the typical extent of anterior temporal lobectomy (i.e., “temporal plus epilepsy”), including portions of the supratemporal plane (STP). Failure to identify this subset of patients and adjust the surgical plan accordingly results in suboptimum surgical outcomes. There are unique technical challenges associated with obtaining recordings from the STP. The authors sought to examine the clinical utility and safety of placing depth electrodes within the STP in patients with TLE.METHODSThis study is a retrospective review and analysis of all cases in which patients underwent intracranial electroencephalography (iEEG) with use of at least one STP depth electrode over the 10 years from January 2006 through December 2015 at University of Iowa Hospitals and Clinics. Basic clinical information was collected, including the presence of ictal auditory symptoms, electrode coverage, monitoring results, resection extent, outcomes, and complications. Additionally, cases in which the temporal lobe was primarily or secondarily involved in seizure onset and propagation were categorized based upon how rapidly epileptic activity was observed within the STP following seizure onsets: within 1 second, between 1 and 15 seconds, after 15 seconds, and not involved.RESULTSFifty-two patients underwent iEEG with STP coverage, with 1 STP electrode used in 45 (86.5%) cases and 2 STP electrodes in the other cases. There were no complications related to STP electrode placement. Of 42 cases in which the temporal lobe was primarily or secondarily involved, seizure activity was recorded from the STP in 36 cases (85.7%): in 5 cases (11.9%) within 1 second, in 5 (11.9%) between 1 and 15 seconds, and in 26 (61.9%) more than 15 seconds following seizure onset. Seizure outcomes inversely correlated with rapid ictal involvement of the STP (Engel class I achieved in 25%, 67%, and 82% of patients in the above categories, respectively). All patients without ictal STP involvement achieved seizure freedom. Only 4 (11.1%) patients with STP ictal involvement reported auditory symptoms.CONCLUSIONSIctal involvement of the STP is common even in the absence of auditory symptoms and can be effectively detected by the STP electrodes. These electrodes are safe to implant and provide useful prognostic information.

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Invasive Insular Sampling in Pediatric Epilepsy: A Single-Institution Experience

Operative Neurosurgery ◽

10.1093/ons/opx253 ◽

2017 ◽

Vol 15 (3) ◽

pp. 310-317 ◽

Cited By ~ 2

Author(s):

Luke D Tomycz ◽

Andrew T Hale ◽

Ali S Haider ◽

Dave F Clarke ◽

Mark R Lee

Keyword(s):

Insular Cortex ◽

Clinical Information ◽

Electrode Placement ◽

Pediatric Epilepsy ◽

Seizure Onset ◽

Single Institution ◽

Invasive Treatment ◽

Depth Electrodes ◽

Depth Electrode ◽

Electrode Insertion

Abstract BACKGROUND It has been increasingly recognized that the insular cortex plays an important role in frontotemporal-parietal epilepsy in children. The insula, however, cannot be properly interrogated with conventional subdural grids, and its anatomy makes it difficult to implicate the insula with semiology or noninvasive modalities. Frame-based, stereotactic placement of insular depth electrodes for direct extraoperative monitoring is a relatively low-risk maneuver that allows for conclusive interrogation of this region, and, in select cases, can easily be replaced with a laser applicator for minimally invasive treatment via thermoablation. OBJECTIVE To describe the largest reported series of pediatric patients with refractory epilepsy undergoing insular depth electrode placement. METHODS We used current procedural terminology billing records to identify cases of depth electrode insertion performed at our institution. Clinical information from patients undergoing invasive insular sampling was then retrospectively collected. RESULTS Seventy-four insular depth electrodes were placed in 49 patients for extraoperative, inpatient monitoring. The decision to place insular depth electrodes was determined by a multidisciplinary epilepsy team. In 65.3% of cases, direct invasive sampling implicated the insula in seizure onset and prompted either thermoablation or surgical resection of some portion of the insula. There were no serious adverse effects or complications associated with the placement of insular depth electrodes. CONCLUSION Given the low morbidity of insular depth electrode insertion and the high proportion of patients who exhibited insular involvement, it is worth considering whether insular depth electrodes should be part of the standard presurgical evaluation in children with treatment-refractory frontotemporal-parietal epilepsy.

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Intracranial Telemetry Recording of Intractable Epilepsy at London Health Sciences

Canadian Journal of Neurological Sciences / Journal Canadien des Sciences Neurologiques ◽

10.1017/s0317167100018114 ◽

2012 ◽

Vol 39 (S6) ◽

pp. S10-S13

Author(s):

David A. Steven ◽

Richard S. McLachlan

Keyword(s):

Epilepsy Surgery ◽

Intractable Epilepsy ◽

Health Sciences ◽

Sufficient Information ◽

Cortical Surface ◽

Foramen Ovale ◽

Seizure Onset ◽

Chronic Recording ◽

Depth Electrodes ◽

London Health

Routine EEG telemetry using scalp electrode recordings is carried out in all patients being considered for epilepsy surgery. However this, along with other testing, may not yield sufficient information about the location of seizure onset to allow a decision regarding surgery to be made. Various methods have been developed to implant electrodes for chronic recording closer to the cortical surface from which seizures arise including the use of sphenoidal, foramen ovale, epidural peg, subdural and depth electrodes. This is a review of the last two techniques particularly as utilized at London Health Sciences Centre.

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Utility of depth electrode placement in the neurosurgical management of bottom-of-sulcus lesions: technical note

Journal of Neurosurgery Pediatrics ◽

10.3171/2019.4.peds18639 ◽

2019 ◽

Vol 24 (3) ◽

pp. 284-292

Author(s):

Eisha A. Christian ◽

Elysa Widjaja ◽

Ayako Ochi ◽

Hiroshi Otsubo ◽

Stephanie Holowka ◽

...

Keyword(s):

Pediatric Patients ◽

Focal Cortical Dysplasia ◽

Target Identification ◽

Cortical Dysplasia ◽

Technical Note ◽

Electrode Placement ◽

Electrode Implantation ◽

Depth Electrodes ◽

Intracranial Electrode ◽

The Brain

OBJECTIVESmall lesions at the depth of the sulcus, such as with bottom-of-sulcus focal cortical dysplasia, are not visible from the surface of the brain and can therefore be technically challenging to resect. In this technical note, the authors describe their method of using depth electrodes as landmarks for the subsequent resection of these exacting lesions.METHODSA retrospective review was performed on pediatric patients who had undergone invasive electroencephalography with depth electrodes that were subsequently used as guides for resection in the period between July 2015 and June 2017.RESULTSTen patients (3–15 years old) met the criteria for this study. At the same time as invasive subdural grid and/or strip insertion, between 2 and 4 depth electrodes were placed using a hand-held frameless neuronavigation technique. Of the total 28 depth electrodes inserted, all were found within the targeted locations on postoperative imaging. There was 1 patient in whom an asymptomatic subarachnoid hemorrhage was demonstrated on postprocedural imaging. Depth electrodes aided in target identification in all 10 cases.CONCLUSIONSDepth electrodes placed at the time of invasive intracranial electrode implantation can be used to help localize, target, and resect primary zones of epileptogenesis caused by bottom-of-sulcus lesions.

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