Determinants of Functional Outcome after Pediatric Hemispherotomy.

OBJECTIVE: We aimed to evaluate determinants of functional outcome after pediatric hemispherotomy in a large and recent multicenter cohort. METHODS: We retrospectively investigated the functional outcomes of 455 children who underwent hemispherotomy at 5 epilepsy centers in 2000-2016. We identified determinants of unaided walking, voluntary grasping with the hemiplegic hand, and speaking through Bayesian multivariable regression modeling using missing data imputation. RESULTS: Seventy-five percent of children were seizure-free, and 44% stopped antiseizure medication at a 5.1-year mean follow-up (range = 1-17.1). Seventy-seven percent of children could walk unaided, 8% could grasp voluntarily, and 68% could speak at the last follow-up. Children were unlikely to walk when they had contralateral magnetic resonance imaging (MRI) abnormalities (40/73, p = 0.04), recurrent seizures following hemispherotomy (62/109, p = 0.04), and moderately (50/61, p = 0.03) or severely impaired (127/199, p = 0.001) postsurgical intellectual functioning, but were likely to walk when they were older at outcome determination (p = 0.01). Children were unlikely to grasp voluntarily with the hand contralateral to surgery when they had Rasmussen encephalitis (0/61, p = 0.001) or Sturge-Weber syndrome (0/32, p = 0.007). Children were unlikely to speak when they had contralateral MRI abnormalities (30/69, p = 0.002) and longer epilepsy duration (p = 0.01), but likely to speak when they had Sturge-Weber syndrome (29/35, p = 0.01), were older at surgery (p = 0.04), and were older at outcome determination (p < 0.001). INTERPRETATION: Etiology and bilaterality of structural brain abnormalities were key determinants of functional outcome after hemispherotomy. Longer epilepsy duration affected language outcomes. Not surprisingly, walking and talking ability increased with older age at outcome evaluation. ANN NEUROL 2024;95:377-387.

Behavioral and brain morphological changes before and after hemispherotomy.

Hemispherotomy is an effective surgery for treating refractory epilepsy from diffuse unihemispheric lesions. To date, postsurgery neuroplastic changes supporting behavioral recovery after left or right hemispherotomy remain unclear. In the present study, we systematically investigated changes in gray matter volume (GMV) before and after surgery and further analyzed their relationships with behavioral scores in two large groups of pediatric patients with left and right hemispherotomy (29 left and 28 right). To control for the dramatic developmental effect during this stage, age-adjusted GMV within unaffected brain regions was derived voxel by voxel using a normative modeling approach with an age-matched reference cohort of 2115 healthy children. Widespread GMV increases in the contralateral cerebrum and ipsilateral cerebellum and GMV decreases in the contralateral cerebellum were consistently observed in both patient groups, but only the left hemispherotomy patients showed GMV decreases in the contralateral cingulate gyrus. Intriguingly, the GMV decrease in the contralateral cerebellum was significantly correlated with improvement in behavioral scores in the right but not the left hemispherotomy patients. Importantly, the preoperative voxelwise GMV features can be used to significantly predict postoperative behavioral scores in both patient groups. These findings indicate an important role of the contralateral cerebellum in the behavioral recovery following right hemispherotomy and highlight the predictive potential of preoperative imaging features in postoperative behavioral performance.

Hemispheric epilepsy surgery for hemimegalencephaly: The UCLA experience.

OBJECTIVES: Hemimegalencephaly (HME) is a rare congenital brain malformation presenting predominantly with drug-resistant epilepsy. Hemispheric disconnective surgery is the mainstay of treatment; however, little is known about how postoperative outcomes compare across techniques. Thus we present the largest single-center cohort of patients with HME who underwent epilepsy surgery and characterize outcomes. METHODS: This observational study included patients with HME at University of California Los Angeles (UCLA) from 1984 to 2021. Patients were stratified by surgical intervention: anatomic hemispherectomy (AH), functional hemispherectomy (FH), or less-than-hemispheric resection (LTH). Seizure freedom, functional outcomes, and operative complications were compared across surgical approaches. Regression analysis identified clinical and intraoperative variables that predict seizure outcomes. RESULTS: Of 56 patients, 43 (77%) underwent FH, 8 (14%) underwent AH, 2 (4%) underwent LTH, 1 (2%) underwent unknown hemispherectomy type, and 2 (4%) were managed non-operatively. At median last follow-up of 55 months (interquartile range [IQR] 20-92 months), 24 patients (49%) were seizure-free, 17 (30%) required cerebrospinal fluid (CSF) shunting for hydrocephalus, 9 of 43 (21%) had severe developmental delay, 8 of 38 (21%) were non-verbal, and 15 of 38 (39%) were non-ambulatory. There was one (2%) intraoperative mortality due to exsanguination earlier in this cohort. Of 12 patients (29%) requiring revision surgery, 6 (50%) were seizure-free postoperatively. AH, compared to FH, was not associated with statistically significant improved seizure freedom (hazard ratio [HR] = .48, p = .328), although initial AH trended toward greater odds of seizure freedom (75% vs 46%, p = .272). Younger age at seizure onset (HR = .29, p = .029), lack of epilepsia partialis continua (EPC) (HR = .30, p = .022), and no contralateral seizures on electroencephalography (EEG) (HR = .33, p = .039) independently predicted longer duration of seizure freedom. SIGNIFICANCE: This study helps inform physicians and parents of children who are undergoing surgery for HME by demonstrating that earlier age at seizure onset, absence of EPC, and no contralateral EEG seizures were associated with longer postoperative seizure freedom. At our center, initial AH for HME may provide greater odds of seizure freedom with complications and functional outcomes comparable to those of FH.

Development of an online calculator for the prediction of seizure freedom following pediatric hemispherectomy using the Hemispherectomy Outcome Prediction Scale (HOPS).

OBJECTIVES: Although hemispheric surgeries are among the most effective procedures for drug-resistant epilepsy (DRE) in the pediatric population, there is a large variability in seizure outcomes at the group level. A recently developed HOPS score provides individualized estimation of likelihood of seizure freedom to complement clinical judgement. The objective of this study was to develop a freely accessible online calculator that accurately predicts the probability of seizure freedom for any patient at 1-, 2-, and 5-years post-hemispherectomy. METHODS: Retrospective data of all pediatric patients with DRE and seizure outcome data from the original Hemispherectomy Outcome Prediction Scale (HOPS) study were included. The primary outcome of interest was time-to-seizure recurrence. A multivariate Cox proportional-hazards regression model was developed to predict the likelihood of post-hemispheric surgery seizure freedom at three time points (1-, 2- and 5- years) based on a combination of variables identified by clinical judgment and inferential statistics predictive of the primary outcome. The final model from this study was encoded in a publicly accessible online calculator on the International Network for Epilepsy Surgery and Treatment (iNEST) website (https://hops-calculator.com/). RESULTS: The selected variables for inclusion in the final model included the five original HOPS variables (age at seizure onset, etiologic substrate, seizure semiology, prior non-hemispheric resective surgery, and contralateral fluorodeoxyglucose-positron emission tomography [FDG-PET] hypometabolism) and three additional variables (age at surgery, history of infantile spasms, and magnetic resonance imaging [MRI] lesion). Predictors of shorter time-to-seizure recurrence included younger age at seizure onset, prior resective surgery, generalized seizure semiology, FDG-PET hypometabolism contralateral to the side of surgery, contralateral MRI lesion, non-lesional MRI, non-stroke etiologies, and a history of infantile spasms. The area under the curve (AUC) of the final model was 73.0%. SIGNIFICANCE: Online calculators are useful, cost-free tools that can assist physicians in risk estimation and inform joint decision-making processes with patients and families, potentially leading to greater satisfaction. Although the HOPS data was validated in the original analysis, the authors encourage external validation of this new calculator.

Pregnancy and delivery after functional hemispherectomy for Rasmussen's encephalitis: a case report.

BACKGROUND: Rasmussen's encephalitis (RE) is a rare neurologic disorder characterized by progressive seizures and unilateral cerebral atrophy with onset during childhood and unknown etiology. When medical therapy appears refractory, surgical disconnection of the affected hemisphere is indicated. Quality of life after functional hemispherectomy is largely good, affected females may therefore pursue pregnancy. However, data on pregnancy and delivery in RE post hemispherectomy is extremely rare. CASE PRESENTATION: We present the case of a patient with left functional hemispherectomy for RE at the age of seven, who experienced two successful pregnancies. In both pregnancies, her post-surgical symptoms including right-sided spasticity, cephalgia, dizziness, and impairment of vision and speech deteriorated but improved to pre-pregnancy level after delivery. Neurologic sequelae post-hemispherectomy overlapped with clinical signs of preeclampsia and required close diagnostic surveillance during both pregnancies. CONCLUSION: There are no data on the interaction between RE, hemispherectomy and pregnancy, making maternal and fetal risk assessment difficult. Due to the complexity of the condition and symptoms, management of RE in pregnancy remains highly challenging and requires an interdisciplinary approach. This is the first case description of two successful pregnancies in a woman with RE and status post-hemispherectomy. Further evidence is urgently required to improve counseling and management of affected women.

Predicting seizure outcomes and functional outcomes after hemispherotomy: are we any better?

INTRODUCTION: Present study attempted to analyze seizure freedom and detailed functional outcomes after functional hemispherotomy and utility of hemispherotomy outcome prediction scale (HOPS) scores in predicting outcomes. METHODS: Patients who underwent functional hemispherotomy were analyzed for clinical presentation, neuroimaging, seizure outcomes, and functional outcomes. RESULTS: A total of 76 procedures were performed on 69 patients. Mean age at the surgery was 8 ± 6.1 years. Fourteen patients were < 2 years. Age of onset epilepsy of the cohort was 2.0 ± 3.3 years. All had severe catastrophic epilepsy with multiple daily seizures. All patients had motor deficits with 36 (52%) patients had contralateral dysfunctional hand. Perinatal stroke (49%) was most common substrate followed by cortical malformations (21.7%). Eight patients had contralateral imaging abnormalities. Fifty-nine (86.76%) patients remained seizure free (Engle 1a) at 41 + -20.9 months. HOPS scores were available for 53 patients and lowest seizure outcome was 71% for HOPS score of 4. Lower HOPS scores predicted better seizure outcomes. Cortical malformations operated earlier than 2 years predicted poor seizure outcomes (66.6%). Positive functional outcomes are recorded in 80% of patients with 78% reporting improvement from the pre-surgical level. Five (7.2%) patients underwent shunt surgery. One mortality recorded. CONCLUSIONS: Hemispherotomy has excellent seizure outcomes. Early surgery in cortical malformations appears to be predictor of poorer seizure outcomes. HOPS score is a good tool to predict the seizure outcomes. Hemispherotomy is perceived to improve the Cognitive and functional performance.

MRI and pathology comparisons in Rasmussen's encephalitis: a multi-institutional examination of hemispherotomy outcomes relative to imaging and histological severity.

PURPOSE: Rasmussen encephalitis (RE) is a very rare chronic neurological disorder of unilateral inflammation of the cerebral cortex. Hemispherotomy provides the best chance at achieving seizure freedom in RE patients, but with significant risks and variable long-term outcomes. The goal of this study is to utilize our multicenter pediatric cohort to characterize if differences in pathology and/or imaging characterization of RE may provide a window into post-operative seizure outcomes, which in turn could guide decision-making for parents and healthcare providers. METHODS: This multi-institutional retrospective review of medical record, imaging, and pathology samples was approved by each individual institution's review board. Data was collected from all known pediatric cases of peri-insular functional hemispherotomy from the earliest available electronic medical records. Mean follow-up time was 4.9 years. Clinical outcomes were measured by last follow-up visit using both Engel and ILAE scoring systems. Relationships between categorical and continuous variables were analyzed with Pearson correlation values. RESULTS: Twenty-seven patients met study criteria. No statistically significant correlations existed between patient imaging and pathology data. Pathology stage, MRI brain imaging stages, and a combined assessment of pathology and imaging stages showed no statistically significant correlation to post-operative seizure freedom rates. Hemispherectomy Outcome Prediction Scale scoring demonstrated seizure freedom in only 71% of patients receiving a score of 1 and 36% of patients receiving a score of 2 which were substantially lower than predicted. CONCLUSIONS: Our analysis did not find evidence for either independent or combined analysis of imaging and pathology staging being predictive for post peri-insular hemispherotomy seizure outcomes, prompting the need for other biomarkers to be explored. Our data stands in contrast to the recently proposed Hemispherectomy Outcome Prediction Scale and does not externally validate this metric for an RE cohort.

Not surgical technique, but etiology, contralateral MRI, prior surgery, and side of surgery determine seizure outcome after pediatric hemispherotomy.

OBJECTIVE: We aimed to assess determinants of seizure outcome following pediatric hemispherotomy in a contemporary cohort. METHODS: We retrospectively analyzed the seizure outcomes of 457 children who underwent hemispheric surgery in five European epilepsy centers between 2000 and 2016. We identified variables related to seizure outcome through multivariable regression modeling with missing data imputation and optimal group matching, and we further investigated the role of surgical technique by Bayes factor (BF) analysis. RESULTS: One hundred seventy seven children (39%) underwent vertical and 280 children (61%) underwent lateral hemispherotomy. Three hundred forty-four children (75%) achieved seizure freedom at a mean follow-up of 5.1 years (range 1 to 17.1). We identified acquired etiology other than stroke (odds ratio [OR] 4.4, 95% confidence interval (CI) 1.1-18.0), hemimegalencephaly (OR 2.8, 95% CI 1.1-7.3), contralateral magnetic resonance imaging (MRI) findings (OR 5.5, 95% CI 2.7-11.1), prior resective surgery (OR 5.0, 95% CI 1.8-14.0), and left hemispherotomy (OR 2.3, 95% CI 1.3-3.9) as significant determinants of seizure recurrence. We found no evidence of an impact of the hemispherotomy technique on seizure outcome (the BF for a model including the hemispherotomy technique over the null model was 1.1), with comparable overall major complication rates for different approaches. SIGNIFICANCE: Knowledge about the independent determinants of seizure outcome following pediatric hemispherotomy will improve the counseling of patients and families. In contrast to previous reports, we found no statistically relevant difference in seizure-freedom rates between the vertical and horizontal hemispherotomy techniques when accounting for different clinical features between groups.

Hemispherotomy in children: A retrospective analysis of 152 surgeries at a single center and predictors for long-term seizure outcome.

OBJECTIVE: Completeness as a predictor of seizure freedom is broadly accepted in epilepsy surgery. We focused on the requirements for a complete hemispherotomy and hypothesized that the disconnection of the insula contributes to a favorable postoperative seizure outcome. We analyzed surgical and nonsurgical predictors influencing long-term seizure outcome before and after a modification of our hemispherotomy technique. METHODS: We retrospectively studied surgical procedures, electroclinical parameters, magnetic resonance imaging (MRI) results, and follow-up data in all children who had undergone hemispherotomy between 2001 and 2018 at our institution. We used logistic regression models to analyze the influence of different factors on seizure outcome. RESULTS: A total of 152 patients were eligible for seizure outcome analysis only. Of these, 140 cases had complete follow-up data for ≥24 months and provide the basis for the following results. The median age at surgery was 4.3 years (range = .3-17.9 years). Complete disconnection (including the insular tissue) was achieved in 63.6% (89/140). At 2-year follow-up, seizure freedom (Engel class IA) was observed in 34.8% (8/23) with incomplete insular disconnection, whereas this was achieved in 88.8% (79/89) with complete surgical disconnection (p < .001, odds ratio [OR] = 10.41). In the latter group (n = 89), a potentially epileptogenic contralateral MRI lesion was the strongest predictor for postoperative seizure recurrence (OR = 22.20). SIGNIFICANCE: Complete surgical disconnection is the most important predictor of seizure freedom following hemispherotomy and requires disconnection of the insular tissue at the basal ganglia level. Even if the hemispherotomy is performed surgically completely, a potentially epileptogenic contralateral lesion on preoperative MRI significantly reduces the chances of postoperative seizure freedom.

Functional outcomes of pediatric hemispherotomy: Impairment, activity, and medical service utilization.

OBJECTIVE: The purpose of this study was to describe the functional outcomes of hemispherotomy in a pediatric cohort, including impairments, activity limitations, utilization of therapies and medical specialist services, and subsequent surgical intervention. METHODS: We conducted a retrospective review of patients who underwent hemispherotomy at UPMC Children's Hospital of Pittsburgh from 2001 to 2021. Data on impairments, activity limitations in mobility, self-care, and communication, and use of re/habilitative therapies and medical specialist services were collected pre-operatively and at 1, 5, 10, and 15 years postoperatively. Seizure outcomes were reported via Engel classification at the longest follow-up interval and subsequent surgical procedures were documented through the latest follow-up interval. RESULTS: A total of 28 patients who underwent hemispherotomy were assessed prior to surgery, 26 at 1 year post-op, 13 at 5 years, 9 at 10 years, and 5 at 15 years. Seizure outcomes at the longest follow-up interval showed that 84.6% of patients were seizure-free. Assessment of impairments to body structure & function from baseline to 1-year post-op revealed increased impairment in 73% of patients, while most patients saw no change in impairment at 5 years (69%), 10 years (100%), and 15 years (100%) post-op compared to the previous time point. Muscle tone abnormalities (100%), hemiparesis (92%), and visual field deficits (85%) were the most frequently observed impairments in the first year following surgery. Most patients saw no change in developmental or cognitive-affective impairments at 1 (65%), 5 (85%), 10 (89%), and 15 years (80%) post-op compared to the previous time point. The only qualitative reports of decreased ability occurred in 2/26 patients whose medical records indicated decreased mobility at the 1-year mark. All further qualitative reports of ability in mobility, self-care, and communication domains indicated increases or no change in ability for all patients at each of the subsequent follow-up intervals. Exploration of the utilization of re/habilitative therapy services shows that 84% of patients received at least one therapy service at baseline, 100% at1 year, 92% at 5 years, 100% at 10 years, and 80% at 15 years post-op. Patients were followed, on average (m), by multiple medical specialist services at baseline (m = 2.58) as well as the 1- (m = 1.70), 5- (m = 2.15), 10- (m = 3.00) and 15-year (m = 3.40) follow-up intervals. Following hemispherotomy, 15 (53.6%) patients required an average of 2.21 additional surgeries. Most often required was orthopedic surgical intervention (n = 16 procedures), followed by shunt placement (n = 7) and revision (n = 14) targeting hydrocephalus. SIGNIFICANCE: This retrospective study demonstrates expected increases in impairments such as hemiparesis and visual field deficits (i.e., homonymous hemianopia) in the context of increased activity and favorable seizure outcomes for 28 pediatric patients who underwent hemispherotomy for drug-resistant epilepsy. Most patients required rehabilitative therapies prior to surgery and continued to require these services post-operatively. Reported baseline functional status, the persistence of impairments following surgery, and comorbidities among this cohort underscore the medical complexity of this patient population and the importance of multidisciplinary care both pre-and post-operatively.

An Initial Experience of Completion Hemispherotomy via Magnetic Resonance-Guided Laser Interstitial Therapy.

INTRODUCTION: In carefully selected patients with medically refractory epilepsy, disconnective hemispherotomy can result in significant seizure freedom; however, incomplete disconnection can result in ongoing seizures and poses a significant challenge. Completion hemispherotomy provides an opportunity to finish the disconnection. We describe the use of magnetic resonance-guided laser interstitial thermal ablation (MRgLITT) for completion hemispherotomy. METHODS: Patients treated with completion hemispherotomy using MRgLITT at our institution were identified. Procedural and seizure outcomes were evaluated retrospectively. RESULTS: Five patients (3 males) underwent six MRgLITT procedures (one child treated twice) for completion hemispherotomy at a median age of 6 years (range 1.8-12.9). Two children had hemimegalencephaly, two had Rasmussen encephalitis, and one had polymicrogyria. All five children had persistent seizures likely secondary to incomplete disconnection after their functional hemispherotomy. The mean time from open hemispherotomy to MRgLITT was 569.5 ± 272.4 days (median 424, range 342-1,095). One patient underwent stereoelectroencephalography before MRgLITT. The mean number of ablation targets was 2.3 ± 0.47 (median 2, range 2-3). The mean length of the procedure was 373 min ± 68.9 (median 374, range 246-475). Four of the five patients were afforded improvement in their neurocognitive functioning and speech performance after ablation, with mean daily seizure frequency at 1 year of 1.03 ± 1.98 (median 0, range 0-5). Two patients achieved Engel Class I outcomes at 1 year after ablation, one was Engel Class III, and two were Engel Class IV. The mean follow-up time was 646.8 ± 179.5 days (median 634, range 384-918). No MRgLITT-related complications occurred. Delayed retreatment (>1 year) occurred in three patients: one child underwent redo ablation and two underwent anatomic hemispherectomy. CONCLUSION: We have demonstrated the feasibility of a minimally invasive approach for completion hemispherotomy using MRgLITT. Delayed retreatment was needed in three patients; thus, further study of this technique with comparison to other surgical techniques is warranted.

Cortical change after a 2-week novel robotic rehabilitation program in children with prior hemispherectomy: pilot imaging study.

INTRODUCTION: Partial preservation of sensory and motor functions in the contralateral extremities after hemispherectomy is likely secondary to cortical reorganization of the remaining hemisphere and can be improved by rehabilitation. This study aims to investigate behavioral and structural cerebral cortical changes that may occur after a 2-week novel robotic rehabilitation program in children with prior anatomic hemispherectomy. METHODS: Five patients with prior anatomic hemispherectomy (average age 10.8 years; all female) participated in a 2-week novel robotic rehabilitation program. Pre- and post-treatment (2 time points) high-resolution structural 3D FSPGR (fast spoiled gradient echo) magnetic resonance images were analyzed to measure cortical thickness and gray matter volume using a locally designed image processing pipeline. RESULTS: Four of the five patients showed improvement in the Fugl-Meyer score (average increase 2.5 + 2.1 SD. Individual analyses identified small increases in gray matter volume near the hand knob area of the primary cortex in three of the five patients. Group analyses identified an increase in cortical thickness near the hand knob area of the primary motor cortex, in addition to other sensorimotor regions. CONCLUSION: This small pilot study demonstrates that potentially rehabilitation-associated cortical changes can be identified with MRI in hemispherectomy patients.

Peri-Insular Hemispherotomy: A Systematic Review and Institutional Experience.

INTRODUCTION: Peri-insular hemispherotomy (PIH) is a hemispheric separation technique under the broader hemispherotomy group, a surgical treatment for patients with intractable epilepsy. Hemispherotomy techniques such as the PIH, vertical parasagittal hemispherotomy (VPH), and modified-lateral hemispherotomy are commonly assessed together, despite significant differences in anatomical approach and patient selection. We aim to describe patient selection, outcomes, and complications of PIH in its own right. METHODS: A systematic review of the literature, in accordance with the Preferred Reporting Items of Systematic Reviews and Meta-Analyses (PRISMA) guidelines, was conducted, with searches of the PubMed and Embase databases. A local series including patients receiving PIH and followed up at the Queensland Children's Hospital between 2014 and 2020 was included. RESULTS: Systematic review of the literature identified 393 patients from 13 eligible studies. Engel class 1 outcomes occurred in 82.4% of patients, while 8.6% developed post-operative hydrocephalus. Hydrocephalus was most common in the youngest patient cohorts. Developmental pathology was present in 114 (40.8%) patients, who had fewer Engel 1 outcomes compared to those with acquired pathology (69.1% vs. 83.7%, p = 0.0167). The local series included 13 patients, 11/13 (84.6%) had Engel class 1 seizure outcomes. Post-operative hydrocephalus occurred in 2 patients (15.4%), and 10/13 (76.9%) patients had worsened neurological deficit. CONCLUSION: PIH delivers Engel 1 outcomes for over 4 in 5 patients selected for this procedure, greater than described in combined hemispherectomy analyses. It is an effective technique in patients with developmental and acquired pathologies, despite general preference of VPH in this patient group. Finally, very young patients may have significant seizure and cognitive benefits from PIH; however, hydrocephalus is most common in this group warranting careful risk-benefit assessment. This review delivers a dedicated PIH outcomes analysis to inform clinical and patient decision-making.

[Hemispherectomy and Hemispherotomy in the Treatment of Drug-Resistant Epilepsy].

Hemispherectomy/hemispherotomy is an important surgical procedure for patients with drug-resistant epilepsy who have a unilateral large epileptogenic lesion associated with neurological deficits, such as hemiparesis. Hemispherotomy consists of corpus callosotomy and dissection of projection fibers into the internal capsule. Hemispherotomy has two major approaches: periinsular lateral hemispherotomy(PIH)and vertical parasagittal hemispherotomy(VH). The white matter is incised along the periinsular sulcus to disrupt the internal capsule before corpus callosotomy is performed within the lateral ventricle in PIH. Corpus callosotomy is performed first with an interhemispheric approach, the lateral ventricle is entered, and the internal capsule is disconnected just lateral to the thalamus in the VH. Both approaches have similar efficacy for seizure control; however, a recent study suggested the possible superiority of VH. The chance of complete seizure freedom for one or two postoperative years has been reported to be 70% or greater. The risk of postoperative hydrocephalus is as high as 20%, particularly in young children. In this article, we present and discuss the surgical anatomy of hemispherotomy techniques.

A simulation study to investigate the use of concentric tube robots for epilepsy surgery.

PURPOSE: Patients with pharmacoresistant refractory epilepsy may require epilepsy surgery to prevent future seizure occurrences. Conventional surgery consists of a large craniotomy with straight rigid tools with associated outcomes of morbidity, large tissue resections, and long post-operative recovery times. Concentric tube robots have recently been developed as a promising application to neurosurgery due to their nonlinear form and small diameter. The authors present a concept study to explore the feasibility of performing minimally invasive hemispherotomy with concentric tube robots. METHODS: A model simulation was used to achieve the optimal design and surgical path planning parameters of the concentric tube robot for corpus callosotomy and temporal lobectomy. A single medial burr hole was chosen to access the lateral ventricles for both white matter disconnections. RESULTS: The concentric tube robot was able to accurately reach the designated surgical paths on the corpus callosum and the temporal lobe. CONCLUSION: In a model simulation, the authors demonstrated the feasibility of performing corpus callosotomy and temporal lobectomy using concentric tube robots. Further advancements in the technology may increase the applicability of this technique for epilepsy surgery to better patient outcomes.

Posterior quadrant disconnection for refractory epilepsy: how I do it.

BACKGROUND: Posterior quadrant disconnection (PQD) is intended to interrupt the propagation of intractable unilateral temporo-parieto-occipital epilepsy. METHOD: An enhanced operative video presents the illustrative case of a total PQD indicated for a 15-year-old boy with Sturge-Weber syndrome suffering from seizure recurrence after a partial PQD. We describe the surgical procedure with emphasis on relevant anatomy and multimodal intraoperative guidance in three steps: (i) parieto-occipital disconnection, (ii) posterior callosotomy, and (iii) temporal disconnection/resection. Pearls and pitfalls of surgical management are discussed. CONCLUSION: PQD is a less invasive surgical option to typical hemispherotomy and hemispherectomy for selected indications of posterior multilobar epilepsy.

Comparison of the real-world effectiveness of vertical versus lateral functional hemispherotomy techniques for pediatric drug-resistant epilepsy: A post hoc analysis of the HOPS study.

OBJECTIVE: This study was undertaken to determine whether the vertical parasagittal approach or the lateral peri-insular/peri-Sylvian approach to hemispheric surgery is the superior technique in achieving long-term seizure freedom. METHODS: We conducted a post hoc subgroup analysis of the HOPS (Hemispheric Surgery Outcome Prediction Scale) study, an international, multicenter, retrospective cohort study that identified predictors of seizure freedom through logistic regression modeling. Only patients undergoing vertical parasagittal, lateral peri-insular/peri-Sylvian, or lateral trans-Sylvian hemispherotomy were included in this post hoc analysis. Differences in seizure freedom rates were assessed using a time-to-event method and calculated using the Kaplan-Meier survival method. RESULTS: Data for 672 participants across 23 centers were collected on the specific hemispherotomy approach. Of these, 72 (10.7%) underwent vertical parasagittal hemispherotomy and 600 (89.3%) underwent lateral peri-insular/peri-Sylvian or trans-Sylvian hemispherotomy. Seizure freedom was obtained in 62.4% (95% confidence interval [CI] = 53.5%-70.2%) of the entire cohort at 10-year follow-up. Seizure freedom was 88.8% (95% CI = 78.9%-94.3%) at 1-year follow-up and persisted at 85.5% (95% CI = 74.7%-92.0%) across 5- and 10-year follow-up in the vertical subgroup. In contrast, seizure freedom decreased from 89.2% (95% CI = 86.3%-91.5%) at 1-year to 72.1% (95% CI = 66.9%-76.7%) at 5-year to 57.2% (95% CI = 46.6%-66.4%) at 10-year follow-up for the lateral subgroup. Log-rank test found that vertical hemispherotomy was associated with durable seizure-free progression compared to the lateral approach (p = .01). Patients undergoing the lateral hemispherotomy technique had a shorter time-to-seizure recurrence (hazard ratio = 2.56, 95% CI = 1.08-6.04, p = .03) and increased seizure recurrence odds (odds ratio = 3.67, 95% CI = 1.05-12.86, p = .04) compared to those undergoing the vertical hemispherotomy technique. SIGNIFICANCE: This pilot study demonstrated more durable seizure freedom of the vertical technique compared to lateral hemispherotomy techniques. Further studies, such as prospective expertise-based observational studies or a randomized clinical trial, are required to determine whether a vertical approach to hemispheric surgery provides superior long-term seizure outcomes.

Pediatric functional hemispherectomy: operative techniques and complication avoidance.

Functional hemispherectomy/hemispherotomy is a disconnection procedure for severe medically refractory epilepsy where the seizure foci diffusely localize to one hemisphere. It is an improvement on anatomical hemispherectomy and was first performed by Rasmussen in 1974. Less invasive surgical approaches and refinements have been made to improve seizure freedom and minimize surgical morbidity and complications. Key anatomical structures that are disconnected include the 1) internal capsule and corona radiata, 2) mesial temporal structures, 3) insula, 4) corpus callosum, 5) parietooccipital connection, and 6) frontobasal connection. A stepwise approach is indicated to ensure adequate disconnection and prevent seizure persistence or recurrence. In young pediatric patients, careful patient selection and modern surgical techniques have resulted in > 80% seizure freedom and very good functional outcome. In this report, the authors summarize the history of hemispherectomy and its development and present a graphical guide for this anatomically challenging procedure. The use of the osteoplastic flap to improve outcome and the management of hydrocephalus are discussed.

Risk factors and results of hemispherotomy reoperations in children.

OBJECTIVE: The goal of this study was to perform an analysis of a single-center experience with hemispherotomy reoperations for refractory hemispheric pediatric epilepsy due to persistence of seizures after initial surgery. The authors also identify possible anatomical and neurophysiological reasons for hemispherotomy failure, as well as risk factors and surgical options for this subgroup of patients. METHODS: A review was performed of the medical records in 18 consecutive cases in which candidates for redo hemispherotomy were treated between 2003 and 2018 at the authors' epilepsy surgery center. Fourteen patients underwent reoperation due to seizure recurrence and were studied herein, whereas in 3 the initial surgical procedure was stopped because of uncontrollable bleeding, and the remaining patient refused to undergo a reoperation in spite of seizure recurrence and went on to have a vagus nerve stimulation device placed. RESULTS: Among the 14 patients whose seizures recurred and in whom reoperations were done, the etiology of epilepsy consisted of 7 cases with malformations of cortical development (50%), 5 cases of Rasmussen encephalitis (35.8%), 1 case of porencephaly (7.1%), and 1 case of Sturge-Weber syndrome (7.1%). Eleven patients had radiological evidence of incomplete disconnection. After reoperation, 6 patients were Engel class IA, 1 was Engel II, 5 were Engel III, and 2 were Engel IV, within a mean follow-up of 48.4 months. CONCLUSIONS: Patients with malformations of cortical development have a higher risk of seizure recurrence, and these malformations comprised the main etiology in the reoperation series. Failure of an initial hemispherotomy usually occurs due to incomplete disconnection and needs to be extensively assessed. Outcomes of reoperation are most often favorable, with acceptable complication rates.

Operative posterior disconnection in epilepsy surgery: Experience with 29 patients.

OBJECTIVE: It has been suggested that multilobar epilepsies caused by lesions restricted to the posterior cerebral quadrant (ie, the parietal, temporal, and occipital lobes) can be treated successfully by a procedure termed posterior disconnection. The objective of the present paper was to identify determinants of the epileptological outcome following posterior disconnection surgery. METHODS: The authors retrospectively analyzed a series of 29 consecutive patients undergoing posterior disconnection surgery between 2005 and 2017 for the treatment of refractory posterior quadrantic epilepsy. Specifically, all presurgical and postoperative magnetic resonance (MR) studies were reviewed to identify cases with an incomplete disconnection, or the presence of a more widespread pathology involving the whole hemisphere rather than only its posterior quadrant. In addition, we reevaluated all presurgical video-electroencephalography (EEG) reports. RESULTS: Seizure-free (International League Against Epilepsy [ILAE] 1) after surgery were 3/3 patients with EEG findings restricted to the posterior quadrant, 0/7 patients who had propagation of epileptic activity to the contralateral frontal lobe, and 11/19 (57.9%) who showed propagation to ipsilateral frontal and/or contralateral posterior. Eleven of 13 (84.6%) patients with purely posterior quadrantic magnetic resonance imaging (MRI) findings (as retrospectively diagnosed by neuroimaging) vs 3/16 (18.8%) cases with additional subtle abnormalities outside the posterior quadrant became seizure-free (P = .001). Eleven of 16 (68.8%) patients with complete disconnections were seizure-free vs only 3/13 (23.0%) cases with leftover temporal lobe tissue with contact to the insula (P = .025, both Fisher's exact test). SIGNIFICANCE: A posterior disconnection is a technically demanding but very effective operation for posterior quadrantic epilepsy. Good epileptologic outcomes require not only that the epileptogenic lesion does not extend beyond the confines of the disconnected cerebral volume but also the absence of subtle MRI abnormalities, more widespread than the clear-cut lesion of the posterior quadrant. Hemispheric or contralateral (particularly frontal) propagation of the epileptic activity may also indicate the presence of a hemispheric rather than posterior quadrantic pathology.