Anterior Corpus Callosotomy Research Articles

Frontal lobe disconnection: How I do it.

The objective of frontal lobe disconnection (FD) is to isolate the frontal lobe without removing brain parenchyma, to achieve epilepsy outcomes comparable to those for frontal lobectomy but with fewer complications, since a large post-operative cavity is not created. Main surgical steps include "Identification of the central sulcus" to ensure the preservation of motor function, and "Frontal lobe disconnection" comprising: 1) fronto-parietal disconnection; 2) fronto-basal disconnection; 3) anterior corpus callosotomy; and 4) insula and basal ganglia disconnection. In performing FD, consideration of the disconnection boundary based on an anatomical understanding of white matter tracts is essential.

Frontal Disconnection for Treating Mild Malformation of Cortical Development with Oligodendroglial Hyperplasia in Epilepsy (MOGHE) in the Frontal Lobe.

Malformation of cortical development is an important cause of drug-resistant epilepsy in young children. Mild malformation of cortical development with oligodendroglial hyperplasia in epilepsy (MOGHE) has been added to the last focal cortical dysplasia (FCD) classification and commonly involves the frontal lobe. The semiology at the onset of epilepsy is dominated by non-lateralizing infantile spasm; the boundaries of the malformation are usually difficult to determine by magnetic resonance imaging (MRI) and positron emission tomography (PET), and electroencephalography (EEG) findings are often widespread. Therefore, the traditional concept and strategy of preoperative evaluation to determine the extent of the epileptogenic zone by comprehensive anatomo-electro-clinical methods are difficult to implement. Frontal disconnection is an effective surgical method for the treatment of epilepsy, but there are few related reports. A total of 8 children with histo-pathologically confirmed MOGHE were retrospectively studied. MOGHE was located in the frontal lobe in all patients, and frontal disconnection was performed. The periinsular approach was used in the disconnective procedures, divided into several surgical steps: the partial inferior frontal gyrus resection, the frontobasal and intrafrontal disconnection, and the anterior corpus callosotomy. One patient presented with a short-term postoperative speech disorder, while another patient exhibited transient postoperative limb weakness. No long-term postoperative complications were observed. At 2 years after surgery, 75% of patients were seizure-free, with cognitive improvement in half of them. This finding suggested that frontal disconnection is an effective and safe surgical procedure for the treatment of MOGHE instead of extensive resection in the frontal lobe.

Using magnetic resonance-guided laser interstitial thermal therapy corpus callosotomy to lateralize a seizure focus for staged surgical approach

New onset refractory status epilepticus (NORSE) is an etiologically heterogeneous condition that is associated with high morbidity and mortality. NORSE is often refractory to medical management prompting a workup for epilepsy surgery. Because NORSE remains etiologically elusive in most cases, surgical evaluations are challenging, especially when the epileptogenic zone (EZ) is not easy to lateralize as can be seen in frontal lobe seizures. Lateralizing a frontal lobe EZ may be challenging due to bilateral synchrony from commissural connections through the corpus callosum and low spatiotemporal resolution of the scalp electroencephalography (EEG). We report a pediatric patient with NORSE presenting with focal impaired awareness seizures clustering into super refractory status epilepticus (SRSE). She required surgical intervention for the treatment of her seizures after failing therapeutic doses of antiseizure medications, anesthetic drips, immunomodulation with methylprednisolone, intravenous immunoglobulin and anakinra, and the ketogenic diet. Despite her semiology being focal, the seizures were not well lateralized on scalp EEG and during phase 2 stereo-EEG (sEEG). Anterior magnetic resonance-guided laser interstitial thermal therapy corpus callosotomy (MRgLITT CC) was performed in a multistage surgical approach to successfully lateralize the EZ with a left-lateralized ictal pattern seen after reimplantation of sEEG electrodes. Our case suggests that minimally invasive MRgLITT CC can be successfully used to lateralize an EZ in frontal lobe epilepsy and that epilepsy surgery should be considered in patients with NORSE with SRSE. We also demonstrate that laser interstitial thermal therapy (LITT), while not always resulting in seizure freedom, can sufficiently disrupt a network to abort status epilepticus and lead to seizure improvements.

Endoscopic callosotomy as a minimally invasive approach to treat paediatric refractory epilepsy: case series.

Endoscopic callosotomy has emerged as a promising and minimally invasive technique for the treatment of refractory epilepsy. This paper aims to review the clinical outcomes and advancements associated with endoscopic callosotomy as a therapeutic option. This study includes 14 Paediatric patients diagnosed and managed at Al-azhar university hospitals. Those 14 patients were studied over 2 years. All patients underwent a corpus callosotomy using the bimanual endoscopic technique. Endoscopic anterior corpus callosotomy was done in 13 patients while one case underwent endoscopic complete callosotomy. The most frequent complication was transient disconnection syndrome followed by transient Urinary incontinence and one case had minor CSF leak. As regard seizure freedom outcome (Engel's Outcome Scale): 4 cases (28.6%) became seizure free (Engle class I), 5 cases (35.7%) with Engle class II, 1 case (7.1%) with Engle class III and 4 cases (28.6%) classify as Engle class IV. As a minimally invasive technique with a favorable impact on cognitive function, less complications and a significant reduction in seizure frequency and severity in the majority of paediatric patients, endoscopic corpus callosotomy offeres substantial benefits in managing refractory epilepsy in paediatric.

Added value of corpus callosotomy following vagus nerve stimulation in children with Lennox-Gastaut syndrome: A multicenter, multinational study.

Lennox-Gastaut syndrome (LGS) is a severe form of epileptic encephalopathy, presenting during the first years of life, and is very resistant to treatment. Once medical therapy has failed, palliative surgeries such as vagus nerve stimulation (VNS) or corpus callosotomy (CC) are considered. Although CC is more effective than VNS as the primary neurosurgical treatment for LGS-associated drop attacks, there are limited data regarding the added value of CC following VNS. This study aimed to assess the effectiveness of CC preceded by VNS. This multinational, multicenter retrospective study focuses on LGS children who underwent CC before the age of 18 years, following prior VNS, which failed to achieve satisfactory seizure control. Collected data included epilepsy characteristics, surgical details, epilepsy outcomes, and complications. The primary outcome of this study was a 50% reduction in drop attacks. A total of 127 cases were reviewed (80 males). The median age at epilepsy onset was 6 months (interquartile range [IQR] = 3.12-22.75). The median age at VNS surgery was 7 years (IQR = 4-10), and CC was performed at a median age of 11 years (IQR = 8.76-15). The dominant seizure type was drop attacks (tonic or atonic) in 102 patients. Eighty-six patients underwent a single-stage complete CC, and 41 an anterior callosotomy. Ten patients who did not initially have a complete CC underwent a second surgery for completion of CC due to seizure persistence. Overall, there was at least a 50% reduction in drop attacks and other seizures in 83% and 60%, respectively. Permanent morbidity occurred in 1.5%, with no mortality. CC is vital in seizure control in children with LGS in whom VNS has failed. Surgical risks are low. A complete CC has a tendency toward better effectiveness than anterior CC for some seizure types.

Influence of extent and age at corpus callosotomy on seizure outcomes. A single center experience.

Corpus callosotomy (CC) is a palliative treatment for drop seizures in patients with drug-resistant nonlocalizable epilepsy. We compared drop seizure outcomes between patients undergoing anterior CC versus complete CC and examined factors impacting outcomes for drop seizures including age at CC and duration of epilepsy. A retrospective review of patients who underwent CC between 2003 and 2022 with a minimum of 6 months postsurgical follow-up was included. Outcome measure for drop seizures included seizure reduction ≥50% from baseline as well as elimination of drop seizures. Thirty-eight patients were included. Overall, ≥50% reduction in drop seizures occurred in nearly 70% (23 out of 33) patients with complete elimination in 58% (19 out of 33). Compared with anterior CC (n = 13), patients undergoing complete CC (n = 25) had increased likelihood of ≥50% reduction (p = 0.006) or elimination (p = 0.024) of drop seizures. Regression analysis showed that complete CC was the primary predictor for improved drop seizure outcomes (elimination, p = 0.014 or ≥50% reduction, p = 0.006), while age at CC and duration of epilepsy did not impact the outcomes. Compared to anterior CC, complete CC was significantly more likely to lead to improvement/freedom from drop seizures. Age at CC or duration of epilepsy did not influence drop seizure outcomes.

Use of an Endoscope Reduces the Size of Craniotomy Without Increasing Operative Time Compared With Conventional Microscopic Corpus Callosotomy.

Corpus callosotomy (CC) is an epilepsy surgery that disconnects the commissural fibers at the corpus callosum, a structure that often plays a key role in propagating seizure activity. CC is particularly beneficial in patients with drop attacks. Less invasive endoscopic surgeries have recently been introduced to some fields of neurosurgery but have not yet become common in epilepsy surgery. Endoscopic surgeries offer better visualization and require a smaller corridor than conventional microscopic surgeries. Here, we presented a case series comparing endoscopic CC with microscopic CC. This 2-center retrospective study involved patients who underwent all types of CC (anterior, total, or posterior CC [pCC]) between January 2014 and May 2022. We excluded patients who underwent additional craniotomy for electrocorticography rather than CC, prior craniotomy, or CC without craniotomy. The primary outcomes were comparing size of craniotomy, operative time, and surgical complications between endoscopic CC and microscopic CC. We included 14 CCs in 11 patients in the endoscopic group and 58 CCs in 55 patients in the microscopic group. No significant difference in age was seen between groups. Craniotomies were significantly smaller in the endoscopic group for anterior (13.36 ± 1.31 cm 2 vs 27.55 ± 3.78 cm 2 ; P = .001), total (14.07 ± 2.54 cm 2 vs 26.63 ± 6.97 cm 2 ; P = .001), and pCC (9.44 ± 1.18 cm 2 vs 30.23 ± 10.76 cm 2 ; P = .002). Moreover, no significant differences in operative time (anterior CC [261 ± 53.11 min vs 298.73 ± 81.08 min, P = .226], total CC [339.5 ± 48.2 min vs 321.39 ± 65.98 min, P = .452], pCC [198 ± 24.73 min vs 242.5 ± 59.12 min, P = .240]), or complication rate were seen. Endoscopic CC is a promising technique requiring a smaller craniotomy than microscopic CC, without significantly increasing operative time or complication rate compared with microscopic CC.

Surgical outcomes of open and laser interstitial thermal therapy approaches for corpus callosotomy in pediatric epilepsy.

Corpus callosotomy (CC) is a palliative surgical intervention for patients with medically refractory epilepsy that has evolved in recent years to include a less-invasive alternative with the use of laser interstitial thermal therapy (LITT). LITT works by heating a stereotactically placed laser fiber to ablative temperatures under real-time magnetic resonance imaging (MRI) thermometry. This study aims to (1) describe the surgical outcomes of CC in a large cohort of children with medically refractory epilepsy, (2) compare anterior and complete CC, and (3) review LITT as a surgical alternative to open craniotomy for CC. This retrospective cohort study included 103 patients <21 years of age with at least 1 year follow-up at a single institution between 2003 and 2021. Surgical outcomes and the comparative effectiveness of anterior vs complete and open versus LITT surgical approaches were assessed. CC was the most common surgical disconnection (65%, n = 67) followed by anterior two-thirds (35%, n = 36), with a portion proceeding to posterior completion (28%, n = 10). The overall surgical complication rate was 6% (n = 6/103). Open craniotomy was the most common approach (87%, n = 90), with LITT used increasingly in recent years (13%, n = 13). Compared to open, LITT had shorter hospital stay (3 days [interquartile range (IQR) 2-5] vs 5 days [IQR 3-7]; p < .05). Modified Engel class I, II, III, and IV outcomes at last follow-up were 19.8% (n = 17/86), 19.8% (n = 17/86), 40.2% (n = 35/86), and 19.8% (n = 17/86). Of the 70 patients with preoperative drop seizures, 75% resolved postoperatively (n = 52/69). No significant differences in seizure outcome between patients who underwent only anterior CC and complete CC were observed. LITT is a less-invasive surgical alternative to open craniotomy for CC, associated with similar seizure outcomes, lower blood loss, shorter hospital stays, and lower complication rates, but with longer operative times, when compared with the open craniotomy approach.

Long-term follow-up seizure outcomes after corpus callosotomy: A systematic review with meta-analysis.

Corpus callosotomy (CC) is appropriate for patients with seizures of a bilateral or diffuse origin, or those with seizures of a unilateral origin with rapid spread to the contralateral cerebral hemisphere. The efficiency of CC in patients with drug-resistant epilepsy is a long-term concern because most articles reporting the surgical results of CC arise from small case series, and the durations of follow-up vary. PubMed, Embase, Cochrane Library, and Web of Science were searched to identify papers published before November 8, 2021. The systematic review was completed following PRISMA guidelines. Outcomes were analyzed by meta-analysis of the proportions. A total of 1644 patients with drug-resistant epilepsy (49 retrospective or prospective case series studies) underwent CC, and the follow-up time of all patients was at least 1year. The rate of complete seizure freedom (SF) was 12.38% (95% confidence interval [CI], 8.17%-17.21%). Meanwhile, the rate of complete SF from drop attacks was 61.86% (95% CI, 51.87%-71.41%). The rates of complete SF after total corpus callosotomy (TCC) and anterior corpus callosotomy (ACC) were 11.41% (95% CI, 5.33%-18.91%) and 6.75% (95% CI, 2.76%-11.85%), respectively. Additionally, the rate of complete SF from drop attacks after TCC was significantly higher than that after ACC (71.52%, 95% CI, 54.22%-86.35% vs. 57.11%, 95% CI, 42.17%-71.49%). The quality of evidence for the three outcomes by GRADE assessment was low to moderate. There was no significant difference in the rate of complete SF between TCC and ACC. TCC had a significantly higher rate of complete SF from drop attacks than did ACC. Furthermore, CC for the treatment of drug-resistant epilepsy remains an important problem for further investigation because there are no universally accepted standardized guidelines for the extent of CC and its benefit to patients. In future research, we will focus on this issue.

Corpus Callosotomy for Non-Localizing Drug Resistant Epilepsy with Drop Attacks

Corpus callosotomy (CC) is a surgical palliative procedure done for a selected group of patients with drug resistant epilepsy (DRE) to stop drop attacks and prevent falls. We performed a retrospective chart review of consecutive patients who underwent CC for DRE with drop attacks at our center between 2015 and 2019. Clinical, imaging details and surgical findings were noted. Clinical outcomes and functional status were evaluated. During the study period, 17 patients underwent corpus callosotomy (Male: Female 14:3). The mean age at surgery was 10.3years (standard deviation-5.85, interquartile range [IQR]=6.5). The mean age at onset of seizure was 2.23years (standard deviation-3.42, IQR=1.5). Preoperative seizure frequency ranged from 2 to 60 attacks per day (median: 20, IQR=36). All patients had atonic seizures/drop attacks. One patient underwent anterior CC and 16 underwent complete CC. Three patients had complications in the postoperative period. The median follow-up was 26months. All patients had cessation of drop attacks immediately following surgery. One patient with anterior CC had a recurrence of drop attacks for which she underwent completion CC. Another patient had recurrent drop attacks 3years later and was found to have a residual callosal connection. Three patients had complete seizure freedom and 4 patients had a <50% reduction in seizure frequency. Our study lends additional support to the efficacy of CC in patients with DRE, with the cessation of drop attacks. It also provided a reasonable reduction in seizure frequency. Complete CC led to better control of drop attacks.

131 Multi-Institutional Study on MRI-guided Laser Interstitial Thermal Therapy for Corpus Callosotomy (MRIgLITT-CC): Technique Variation, Ablation Coverage, and Need for Additional Surgery

INTRODUCTION: MRI-guided laser interstitial thermal therapy for corpus callosotomy (MRIgLITT-CC) offers palliation of intractable drop events and atonic, tonic, and generalized tonic-clonic seizures. METHODS: This multi-institutional retrospective study included pediatric patients with medically intractable epilepsy undergoing MRIgLITT-CC. Surgical details, post-operative radiographic results, and need for additional epilepsy surgery were recorded. Percent coverages of the intended ablation zones (anterior, complete, or posterior corpus callosotomy) were estimated from MRI. Data were summarized using descriptive statistics and compared using Chi-square tests. RESULTS: A total of 27 subjects (18 male, 9 female) with mean age 13 years +/- 5 years (4 years, 21 years) underwent planned complete (13, 48%), anterior (11, 41%), or posterior (3, 11%) MRIgLITT-CC. Planned complete MRIgLITT-CC entailed 2 (1/13, 8%), 3 (6/13, 46%), or 4 (6/13, 46%) trajectories with 100% (8/13, 62%) or 95-99% (5/13, 38%) coverage of the planned callosal ablation zone. Anterior MRIgLITT-CC cases included 1 (1/11, 9%), 2 (8/11, 73%), or 3 (1/11, 9%) trajectories to achieve 100% (7/11, 64%), 95-99% (2/11, 18%), 90-94% (1/11, 9%), or &lt;90% (1/11, 9%) coverage of the planned callosal ablation zone. There were no significant differences in percent coverage of intended ablation zone as a function of trajectory number (p = 0.6). Three subjects (11%) required repeat callosal surgery while four subjects (15%) underwent additional vagus nerve stimulator (VNS) insertion during clinic follow-up (mean 11.7 months +/-10.6 months; [0.4 months, 37.1 months]). The need for repeat callosal surgery differed significantly between subjects with 100% and less than 100% ablation coverage (0/16 vs. 3/11, p = 0.03). CONCLUSION: In this multi-institutional study, MRIgLITT-CC yielded 100% or 95-99% coverage of the intended callosal ablation zone in most subjects. Trajectory variation between centers did not impact percent coverage of the intended ablation zone. Few subjects required repeat callosal surgery, particularly those with less than 100% ablation zone coverage, or additional VNS insertion.

The Fornix May Play a Key Role in Korsakoff's Amnesia Secondary to Subcallosal Artery Infarction.

Background: Subcallosal artery infarction injures the fornix and anterior corpus callosum and sometimes causes Korsakoff’s amnesia. We hypothesized that Korsakoff’s amnesia might be caused by fornix dysfunction rather than anterior corpus callosum dysfunction in subcallosal artery infarction. Methods: A systematic review approach was applied to search PubMed and Google Scholar for articles to compare patients who had both bilateral fornix and corpus callosum infarction due to subcallosal artery territory ischemia (vascular event group; V group) with patients who had undergone anterior corpus callosotomy (callosotomy group; C group). Results: The V group comprised 10 patients (mean age, 63 years; median, 69 years; standard deviation (SD), 14.5 years; 5 males, 5 females). The C group comprised 6 patients (mean age, 23.7 years; median, 20 years; SD, 7.3 years; 3 males, 3 females). Six of 10 patients (60%) with subcallosal artery infarction exhibited Korsakoff’s amnesia. One patient showed neither confabulation nor amnesia. Conversely, no amnesia episodes were seen in any patients from the C group (p = 0.034). Conclusion: Fornix injury, rather than anterior corpus callosum injury, might be the major cause of Korsakoff’s amnesia in patients with subcallosal artery infarction.

Intelligence Quotient Outcome Following Epilepsy Surgery in Pediatric Age – A Systematic Review and Meta-Analysis

There is a deep-rooted correlation between refractory epilepsy in pediatric age and intelligence development. However, little is known about whether surgical procedures used in pediatric epilepsy treatment can affect Intelligence Quotient (IQ) or not. Factors that might influence postoperative IQ are also a matter of study in several articles. To tackle these issues, a systematic review with meta-analysis was conducted with the terms “epilepsy”, “epileptic”, “surgery”, “surgical”, “Wechsler Scale” and “intelligence tests” in PubMed, the Cochrane Library, EMBASE and Clinical Trials.gov. A descriptive data synthesis was carried out to address each of the objectives and then a metaanalysis using a random effects model was conducted. A meta-regression was performed to ascertain possible factors that could influence postoperative IQ. The meta-analysis of the studies included found a mean difference between postoperative and preoperative full-scale IQ values of 1.014 standardized points (p &lt; 0.001). Among all the articles regarding curative surgeries, only three reported an overall significant improvement in IQ after surgery. Regarding palliative procedures, both studies with anterior corpus callosotomy reported a significant improvement in full-scale IQ values two years after surgery. The meta-regression performed did not find any predictors of change in full-scale IQ.

Comparison of seizure outcomes and ADL recovery period after total or anterior corpus callosotomy in adolescent and young adults with drop attacks and severe mental retardation

PurposeThe aim of this study was to evaluate seizure outcomes and postoperative neurologic complications, with an emphasis on the recovery period of activities of daily living (ADL) between anterior partial corpus callosotomy (ACC) and total corpus callosotomy (TCC) in adolescent and young adults with drop attacks and severe mental retardation. MethodsWe retrospectively reviewed the clinical records of consecutive patients with intractable epilepsy who underwent corpus callosotomy (CC) for drop attacks between 2010 and 2019 in the Department of Neurosurgery, Hiroshima University hospital, with a minimum follow-up of one year. Inclusion criteria of this study were 1) age at surgery: 11–39 years, 2) preoperative intelligence quotient <35, and 3) preoperative Barthel index (BI) ≥30. Postoperative full ADL recovery was defined as complete recovery to the preoperative BI score. We compared the postoperative days required for 1) recovery of oral intake ability, 2) discharge from our hospital, 3) returning home from any hospital, 4) returning home with full ADL recovery, and 5) seizure outcomes in patients with ACC versus those with one-stage TCC. ResultsTen patients with ACC and 14 patients with one-stage TCC met the inclusion criteria. The period for returning home with full ADL recovery was a median of 15 days (range 9−45 days) after ACC, while the median was 21.5 days (range 10−62 days) after one-stage TCC (p = 0.2904). Although there was a tendency for the ADL recovery period to be longer after one-stage TCC, there were no statistically significant differences in any category of ADL recovery period. Eleven of 14 (78.6 %) patients who received a one-stage TCC showed favorable seizure outcomes, with drop attack cessation, which was significantly better than 1 of 10 (10 %) patients with ACC (p = 0.0009). ConclusionsFrom the viewpoint of postoperative seizure outcomes and ADL recovery period, one-stage TCC is preferred to ACC for adolescent and young adults with severe mental retardation.

Microscopic Anterior Callosotomy for Management of Intractable Epilepsy (Al-Azhar Experience)

Background: Anterior Corpus Callosotomy is a palliative treatment for drug-resistant generalized or multifocal epilepsy patients where focus excision is not an option for management. Callosotomy prevents propagation of epileptic discharge from one cerebral hemisphere to the other. Objective: To describe Al-Azhar University Hospitals experience and clinical outcome of Anterior Corpus Callosotomy for management of drug-resistant generalized epilepsy patients as an inexpensive palliative method. Patients and Methods: In this study, there are 15 patients admitted to Neurosurgery Department in Al-Azhar University Hospitals with drug-resistant generalized epilepsy. These patients were not candidates for lesionectomy. They were managed by anterior two thirds Corpus Callosotomy between February 2017 and December 2019. They were followed at outpatient clinic for at least 14 months. Clinical outcome regarding seizure control was assessed using Engel classification. Results: All 15 patients in this study underwent anterior two thirds corpus callosotomy and followed for at least 14 months. The post-operative improvement of seizure frequency has been evaluated using Engel outcome scale with 12 patients (80%) of the patients becoming Engel class II and 3 patients (20%) becoming Engel class III. Only 3 patients (20%) had minor transient postoperative complications; one patient (6.67%) had contra-lateral lower limb heaviness Grade 4 which was transient, one patient (6.67%) had contra-lateral lower limb Jacksonian focal fits and one patient (6.67%) had behavioral changes for one month. Conclusion: Corpus callosotomy is a palliative procedure and inexpensive method for management of patients with intractable focal with generalization and generalized drug-resistant epilepsy who are not suitable for resective surgery and with good outcome.

Changes in cognitive function after resection of lesions in the anterior part of the lateral ventricle via an interhemispheric transcallosal approach

Anterior callosotomy to about 20 mm has been considered relatively safe empirically. The present study aimed to compare cognitive function before and after resection of tumors in the anterior part of the lateral ventricle. We analyzed 6 patients with intraventricular tumors located in the anterior horn or body of the lateral ventricle who underwent surgical excision via interhemispheric transcallosal approach at Osaka City University Hospital between March 2015 and August 2018. And clinical and imaging studies, neuropsychological function using MMSE, WAIS-III and WMS-R and surgical complications were retrospectively reviewed based on the medical records at our institution. As a result, 4 patients achieved gross total resection of the tumor and 2 patients achieved subtotal resection. 4 patients showed hydrocephalus, which disappeared in each case within 6 months after tumor resection. Mean length of callosotomy was 16.9 mm (range, 15.5–26.1 mm). One patient showed postoperative transient deficits including aphasia, microphonia, ballism in all extremities and hemiplegia, and another patient experienced subjective difficulty when talking. These symptoms disappeared within 3 months after tumor resection. Scores from the MMSE and WAIS-III showed no significant postoperative deterioration. Performance intelligence quotient (P = 0.04), full intelligence quotient (P = 0.04) and perceptual organization (P = 0.03) of WAIS-III were significantly improved after surgery compared with preoperatively. In conclusion, anterior corpus callosotomy of about 20 mm for intraventricular tumor in the anterior horn or body of the lateral ventricle might have little effect on cognitive function in the chronic phase, although the influence of hydrocephalus cannot be ignored.

Stereotactic laser anterior corpus callosotomy for Lennox-Gastaut syndrome.

Corpus callosotomy is an effective palliative treatment for drug-resistant Lennox-Gastaut syndrome (LGS). Laser interstitial thermal therapy has been increasingly used in the treatment of epilepsy. Here, we assess the safety and effectiveness of minimally invasive stereotactic laser anterior corpus callosotomy (SLACC) for drop attacks in LGS. We reviewed sequential cases of patients with medically intractable LGS who underwent SLACC using a two-cannula technique between November 2014 and July 2019. Pre- and postoperative magnetic resonance imaging was used to measure the anteroposterior length of callosal ablation (contrast-enhancing lesion) and estimated disconnection (gap in tract projections on diffusion tensor imaging). Patients were followed longitudinally to assess clinical outcomes. Ten patients were included in this study. The median age was 33 (range = 11-52) years, median duration of epilepsy was 26 (range = 10-49) years, and median duration of postoperative follow-up was 19 (range = 6-40) months. In the anteroposterior direction, 53±7% (mean±SD) of the corpus callosum was ablated and 62±19% of the corpus callosum was estimated to be disconnected. Six (60%) of 10 patients achieved >80% seizure reduction, two (20%) of whom became seizure-free. Eight (80%) patients had >80% reduction in drop attacks, five (50%) of whom became free of drop attacks. Three patients subsequently underwent laser posterior callosotomy with further improvement in drop attacks and/or overall seizure frequency. One patient had an asymptomatic intracerebral hemorrhage along the cannula tract. One patient developed significant aggression after becoming seizure-free. Seizure outcomes following SLACC were comparable to previously reported outcomes of open callosotomy, with reasonable safety profile. SLACC appears to be an effective alternative to open anterior corpus callosotomy with minimal postoperative discomfort and a short recovery period.

S195 Physiological properties of the seizure onset zone and brain connectivity: Insights gained from callosotomy procedures

Introduction Rapidly propagating frontal lobe seizures that are difficult to lateralize may do so after corpus callosotomy. We performed callosotomy using laser interstitial thermal therapy (LITT) in three patients who were undergoing stereoelectroencephalography (SEEG) and examined both the electrocorticogram electrophysiology and neuroimaging connectivity measures. Methods SEEG electrodes were placed three patients with suspected underlying laterization. All three patients underwent anterior corpus callosotomy using stereotactic laser interstitial ablation with electrodes in place (e.g. Fig. 1). Resting fMRI, diffusion tractography were obtained one week before electrode implantation and one week after. In addition, the resting electrocorticogram and corticocortical evoked potential mapping were performed before and after the callosotomy procedure using the same electrodes that were rigidly held in place with skull bolts, resulting in minimal electrode migration after callosotomy. Results All patients had marked lateralization of both interictal activity (Fig. 3) as well as seizure onset (Fig. 4). Alterations in interhemispheric connectivity was reliably demonstrated using DTI and resting fMRI. This was paralleled by a similar changes in resting electrocorticography and corticocortical evoked potentials over areas with projections to the area of the callosum that was lesioned. Both intrahemispheric connectivity as well as interhemispheric connectivity beyond the callosotomy were relatively maintained as reflected by electrocorticographic- and MRI-based measures. Conclusions Callosotomy using LITT may be used in conjunction with SEEG to accurately identify ictal onset in cases where seizure lateralization is difficult. Our results further confirm the correspondence of MRI- and electrophysiological-based connectivity measures by showing that alterations of function connectivity occur using both methods after surgical disconnection.

Trans-falcine and contralateral sub-frontal electrode placement in pediatric epilepsy surgery: technical note.

Phase II monitoring with intracranial electroencephalography (ICEEG) occasionally requires bilateral placement of subdural (SD) strips, grids, and/or depth electrodes. While phase I monitoring often demonstrates a preponderance of unilateral findings, individual studies (video EEG, single photon emission computed tomography [SPECT], and positron emission tomography [PET]) can suggest or fail to exclude a contralateral epileptogenic onset zone. This study describes previously unreported techniques of trans-falcine and sub-frontal insertion of contralateral SD grids and depth electrodes for phase II monitoring in pediatric epilepsy surgery patients when concern about bilateral abnormalities has been elicited during phase I monitoring. Pediatric patients with medically refractory epilepsy undergoing stage I surgery for phase II monitoring involving sub-frontal and/or trans-falcine insertion of SD grids and/or depth electrodes at the senior author's institution were retrospectively reviewed. Intra-operative technical details of sub-frontal and trans-falcine approaches were studied, while intra-operative complications or events were noted. Operative techniques included gentle subfrontal retraction and elevation of the olfactory tracts (while preserving the relationship between the olfactory bulb and cribriform plate) to insert SD grids across the midline for coverage of the contralateral orbito-frontal regions. Trans-falcine approaches involved accessing the inter-hemispheric space, bipolar cauterization of the anterior falx cerebri below the superior sagittal sinus, and sharp dissection using a blunt elevator and small blade scalpel. The falcine window allowed contralateral SD strip, grid, and depth electrodes to be inserted for coverage of the contralateral frontal regions. The study cohort included seven patients undergoing sub-frontal and/or trans-falcine insertion of contralateral SD strip, grid, and/or depth electrodes from February 2012 through June 2015. Five patients (71%) experienced no intra-operative events related to contralateral ICEEG electrode insertion. Intra-operative events of frontal territory venous engorgement (1/7, 14%) due to sacrifice of anterior bridging veins draining into the SSS and avulsion of a contralateral bridging vein (1/7, 14%), probably due to prior anterior corpus callosotomy, each occurred in one patient. There were no intra-operative or peri-operative complications in any of the patients studied. Two patients required additional surgery for supplemental SD strip and/or depth electrodes via burr hole craniectomy to enhance phase II monitoring. All patients proceeded to stage II surgery for resection of ipsilateral epileptogenic onset zones without adverse events. Trans-falcine and sub-frontal insertion of contralateral SD strip, grid, and depth electrodes are previously unreported techniques for achieving bilateral frontal coverage in phase II monitoring in pediatric epilepsy surgery. This technique obviates the need for contralateral craniotomy and parenchymal exposure with limited, remediable risks. Larger case series using the method described herein are now necessary.

Efficacy and safety of corpus callosotomy after vagal nerve stimulation in patients with drug-resistant epilepsy.

OBJECTIVE Vagal nerve stimulation (VNS) and corpus callosotomy (CC) have both been shown to be of benefit in the treatment of medically refractory epilepsy. Recent case series have reviewed the efficacy of VNS in patients who have undergone CC, with encouraging results. There are few data, however, on the use of CC following VNS therapy. METHODS The records of all patients at the authors' center who underwent CC following VNS between 1998 and 2015 were reviewed. Patient baseline characteristics, operative details, and postoperative outcomes were analyzed. RESULTS Ten patients met inclusion criteria. The median follow-up was 72 months, with a minimum follow-up of 12 months (range 12-109 months). The mean time between VNS and CC was 53.7 months. The most common reason for CC was progression of seizures after VNS. Seven patients had anterior CC, and 3 patients returned to the operating room for a completion of the procedure. All patients had a decrease in the rate of falls and drop seizures; 7 patients experienced elimination of drop seizures. Nine patients had an Engel Class III outcome, and 1 patient had a Class IV outcome. There were 3 immediate postoperative complications and 1 delayed complication. One patient developed pneumonia, 1 developed transient mutism, and 1 had persistent weakness in the nondominant foot. One patient presented with a wound infection. CONCLUSIONS The authors demonstrate that CC can help reduce seizures in patients with medically refractory epilepsy following VNS, particularly with respect to drop attacks.