Peri-insular Hemispherotomy: Surgical Principles and Anatomy

Comparison of Hemispheric Surgery Techniques for Pediatric Drug-Resistant Epilepsy: An Individual Patient Data Meta-analysis

BACKGROUND AND OBJECTIVES

Hemispheric surgery effectively treats unihemispheric pediatric drug-resistant epilepsy (DRE) by resecting and/or disconnecting the epileptic hemisphere. Modifications to the original anatomic hemispherectomy have generated multiple functionally equivalent, disconnective techniques for performing hemispheric surgery, termed functional hemispherotomy. While a myriad of hemispherotomy variants exist, all of them can be categorized according to the anatomic plane they are performed in, which includes vertical approaches at or near the interhemispheric fissure and lateral approaches at or near the Sylvian fissure. This meta-analysis of individual patient data (IPD) aimed to compare seizure outcomes and complications between the hemispherotomy approaches to better characterize their relative efficacy and safety in the modern neurosurgical treatment of pediatric DRE, given emerging evidence that outcomes may differ between them.

METHODS

CINAHL, Embase, PubMed, and Web of Science were searched from inception to September 9, 2020, for studies reporting IPD from pediatric patients with DRE who underwent hemispheric surgery. Outcomes of interest were seizure freedom at last follow-up, time-to-seizure recurrence, and complications including hydrocephalus, infection, and mortality. The χ2 test compared the frequency of seizure freedom and complications. Multivariable mixed-effects Cox regression controlling for predictors of seizure outcome was performed on propensity score-matched patients to compare time-to-seizure recurrence between approaches. Kaplan-Meier curves were made to visualize differences in time-to-seizure recurrence.

RESULTS

Fifty-five studies reporting on 686 unique pediatric patients treated with hemispheric surgery were included for meta-analysis. Among the hemispherotomy subgroup, vertical approaches resulted in a greater proportion of seizure free patients (81.2% vs 70.7%, p = 0.014) than lateral approaches. While there were no differences in complications, lateral hemispherotomy had higher rates of revision hemispheric surgery due to incomplete disconnection and/or recurrent seizures than vertical hemispherotomy (16.3% vs 1.2%, p < 0.001). After propensity score matching, vertical hemispherotomy approaches independently conferred longer time-to-seizure recurrence than lateral hemispherotomy approaches (hazard ratio 0.44, 95% CI 0.19-0.98).

DISCUSSION

Among functional hemispherotomy techniques, vertical hemispherotomy approaches confer more durable seizure freedom than lateral approaches without compromising safety. Future prospective studies are required to definitively determine whether vertical approaches are indeed superior and how it should influence clinical guidelines for performing hemispheric surgery.

Surgical Strategy for Hemispherotomy

Hemispherotomy is a radical treatment for drug-resistant epilepsy that targets developmental, acquired, and progressive diseases with widespread epileptogenic regions in one cerebral hemisphere. Currently, two main approaches are utilized after repeated improvements: lateral and vertical approaches. With the lateral approach, the surgical field is wide, and the approach to the lateral ventricle is relatively easy. On the other hand, the vertical approach has the advantage of reducing intraoperative bleeding and operating time as the resection line of the radial fiber is short, and understanding the three-dimensional anatomy is relatively easy. The lateral approach is generally used for atrophic lesions, whereas the vertical approach is for hypertrophic lesions. Hemispherotomy is expected to not only suppress epileptic seizures but also improve psychomotor development by protecting the unaffected cerebral hemisphere. However, this method is one of the most invasive surgeries in epilepsy surgery, and it is important to fully consider its indications. Furthermore, understanding the neural fiber pathway is important for actual surgery.

Application of 3D Printing Support Material for Neurosurgical Simulation

Brain dissection, an intricate neurosurgical skill, is central to life-saving procedures such as intrinsic brain tumor excision and resective epilepsy surgery. The aims of this manuscript are to outline the selection process of a suitable material for the development of a dissectible brain simulator and to present the use of support material, SUP 706, manufactured by Stratasys Ltd. as a non-waste alternative for sustainably engineering solutions for surgical education. A feasibility study was conducted through qualitative function deployment (QFD) followed by a material selection process. End-user requirements and manufacturing product characteristics were incorporated into the workflow. Three materials, silicone, TissueMatrix™ and support material each formed the primary component of the first two prototypes. Expert feedback, manufacturing cost, safety profiling, functional fidelity and post-processing time data were collected and analyzed. The unique break-away feature of moist support material was found to be more suitable than using silicone or TissueMatrix™ for demonstrating brain dissection techniques. In addition, support material displayed higher functional fidelity by mimicking surgical tissues such as pia mater, gray and white matter, and blood vessels. The cost of the support material prototype was 39% less that of TissueMatrix™ and roughly the same as the silicone model. It took twice as long to post-process the support material prototype than it did the TissueMatrix™ design. Support material lost its ideal dissection properties and began to disintegrate after 30 - 45 minutes. In conclusion 3D printer support material is a low-cost material for a dissectible brain simulator.Clinical Relevance- The use of support material as the primary material in developing a dissectible brain simulator is a promising way of advancing neurosurgical education.

From Resection to Disconnection for Seizure Control in Pediatric Epilepsy Children

Epilepsy surgery revealed dramatically improved seizure outcomes over medical therapy in drug-resistant epilepsy patients. Children with epilepsy, however, have multiple epileptic focuses which require multilobar resection for better seizure outcome. Multilobar resection has not only the several severe surgical complications, such as hydrocephalus and shunt-related craniosynostosis, due to intracranial volume reduction. Isolation method (disconnection surgery) was progressively studied over epileptic focus removal (resective surgery) for seizure control. This concept was first introduced for functional hemispherotomy, and its primary principle is to preserve the vital vascularized brain that is functionally disconnected from the contralateral healthy brain. Currently in most epilepsy centers, the predominant disconnection surgical methods, including functional hemispherotomy, are continually being refined and are showing excellent results. They allow the functional isolation of the hemisphere or multi-lobe, affected by severe epilepsy. This review describes recent findings concerning the indication, surgical technique, seizure outcome and complications in several disconnection surgeries including the functional hemispherotomy for refractory pediatric epilepsy.

Seizure freedom after functional hemispherectomy and a possible role for the insular cortex: the Dutch experience

OBJECT

The authors undertook this study to identify predictors of persistent postoperative seizures in their group of 28 Dutch pediatric and adolescent patients with medically intractable epilepsy who underwent functional hemispherectomy.

METHODS

The records of 28 pediatric and adolescent patients who underwent a functional hemispherectomy in the University Medical Center Utrecht were retrospectively analyzed. The authors performed a Cox regression analysis, using the first postoperative seizure as the event. Pathology, age at surgery, age at seizure onset, duration of epilepsy, type of surgery, surgeon, possible incomplete disconnection on MR images, and presence of residual insular cortex were analyzed as potential associated variables during the follow-up period.

RESULTS

The patients' mean age at surgery was 69.9 months (range 3.0-294.2 months) and mean duration of follow-up was 39.0 months (range 6.0-132.0 months). Six patients had postoperative seizures (21%). One patient had persistent bilateral status epilepticus and died 4 months after surgery. The Cox regression analysis showed presence of insular cortex to be the only variable statistically associated with postoperative seizures (p = 0.021) in this group of 28 patients.

CONCLUSIONS

In this group of Dutch pediatric and adolescent patients, residual insular cortex was positively correlated with persistent postoperative seizures. Given the small sample size in this study, however, caution should be used in drawing conclusions about the role of the insular cortex.

Hemispheric surgery in children with refractory epilepsy: seizure outcome, complications, and adaptive function

PURPOSE

To describe seizure control, complications, adaptive function and language skills following hemispheric surgery for epilepsy.

METHODS

Retrospective chart review of patients who underwent hemispheric surgery from July 1993 to June 2004 with a minimum follow-up of 12 months.

RESULTS

The study population comprised 24 children, median age at seizure onset six months and median age at surgery 41 months. Etiology included malformations of cortical development (7), infarction (7), Sturge-Weber Syndrome (6), and Rasmussen's encephalitis (4). The most frequent complication was intraoperative bleeding (17 transfused). Age <2 yr, weight <11 kg, and hemidecortication were risk factors for transfusion. Postoperative complications included aseptic meningitis (6), and hydrocephalus (3). At median follow-up of 7 yr, 79% of patients are seizure free. Children with malformations of cortical development and Rasmussen's encephalitis were more likely to have ongoing seizures. Overall adaptive function scores were low, but relative strengths in verbal abilities were observed. Shorter duration of epilepsy prior to surgery was related significantly to better adaptive functioning.

CONCLUSIONS

Hemispheric surgery is an effective therapy for refractory epilepsy in children. The most common complication was bleeding. Duration of epilepsy prior to surgery is an important factor in determining adaptive outcome.

Outcome of hemispheric surgeries for refractory epilepsy in pediatric patients

BACKGROUND

Hemispheric brain lesions are commonly associated with early onset of catastrophic epilepsies and multiple seizure types. Hemispheric surgery is indicated for patients with unilateral intractable epilepsy. Although described more than 50 years ago, several new techniques for hemispherectomy have only recently been proposed aiming to reduce operatory risks and morbidity.

MATERIALS AND METHODS

We present the clinical characteristics, presurgical workup, and postoperative outcome of a series of pediatric patients who underwent hemispherectomy for medically intractable epileptic seizures. Thirty-nine patients with medically intractable epilepsy underwent surgery from 1996 to 2005.

RESULTS AND DISCUSSION

We analyzed demographic data, interictal and ictal EEG findings, age at surgery, surgical technique and complications, and postsurgical seizure outcome. There were 74.4% males. Tonic and focal motor seizures occurred in 30.8 and 20.5% of the patients. Most frequent etiologies were Rasmussen encephalitis (30.8%) and malformation of cortical development (23.1%). Postsurgical outcomes were Engel classes I and II for 61.5% of the patients. In general, 89.5% of the patients exhibited at least a 90% reduction in seizure frequency. All patients had acute worsening of hemiparesis after surgery. Basically, two surgical techniques have been employed, both with similar results, although a trend has been noted toward one of the procedures which produced consistently complete disconnection. Patients with hemispheric brain lesions usually have abnormal neurological development and intractable epilepsy. When video-EEG monitoring and magnetic resonance imaging show unilateral disease, the patient may evolve with a good surgical outcome. We showed that a marked reduction in seizure frequency may be achieved, with acceptable neurological impairments.

Surgical treatment of epilepsy in Sturge-Weber syndrome in children

OBJECT

The authors sought to analyze the success rate of surgery in the management of medically intractable epilepsy in children with Sturge-Weber syndrome and to determine whether the extent and timing of surgery affected seizure and developmental outcomes.

METHODS

The authors performed a retrospective review of 27 children who underwent surgery at their institution for medically resistant epilepsy, and they examined the outcomes with regard to epilepsy control and neuropsychological development. Seventeen children (63%) experienced onset of their epilepsy when they were younger than 1 year of age. These patients were significantly more likely to have hemiparesis (p < or =0.001) and status epilepticus (p < or = 0.001) and be developmentally delayed (p < or = 0.025) than children whose epilepsy started later in life. Eight patients underwent a hemispherectomy (either anatomical or functional), and complete resolution of epilepsy was noted in all. Of the 19 patients in whom a focal resection was performed, 11 (58%) became seizure free. The 10 children in whom there was residual disease were more likely to have continuing epilepsy than the nine whose lesions were completely excised (p< or = 0.05). Seventeen children exhibited improvement in their developmental status following surgery. This improvement was significantly affected by completeness of resection (p< or = 0.05) and age at surgery (p< or = 0.009). Seizure freedom per se was not affected by the timing of surgery.

CONCLUSIONS

Medically intractable epilepsy in children can be treated effectively by surgery. The degree of resection or disconnection of diseased tissue, but not patient age at the time of surgery, is an important factor in achieving epilepsy control. Early surgery is more likely to improve developmental outcome.

Hemispherectomy: a schematic review of the current techniques

Anatomical hemispherectomy has been used for the treatment of seizures since 1938. However, it was almost abandoned in the 1960s after reports of postoperative fatalities caused by hydrocephalus, hemosiderosis, and trivial head traumas. Despite serious complications, the remarkable improvement of patients encouraged authors to carry out modifications on anatomical hemispherectomy in order to lessen its morbidity while preserving its efficacy. The effort to improve the technique generated several original procedures. This paper reviews current techniques of hemispherectomy and proposes a classification scheme based on their surgical characteristics. Techniques of hemispherectomy were sorted into two major groups: (1) those that remove completely the cortex from the hemisphere and (2) those that associate partial cortical removal and disconnection. Group 1 was subdivided into two subgroups based on the integrity of the ventricular cavity and group 2 was subdivided into three subgroups depending on the amount and location of the corticectomy. Grouping similar techniques may allow a better understanding of the distinctive features of each one and creates the possibility of comparing data from different authors.