Hemispherotomy

Functional hemispherectomy/hemispherotomy is a disconnective procedure that has undergone significant evolution. Today, when performed in high-volume epilepsy centers in appropriate patients, it is an effective procedure for the control of unilateral medically refractory epilepsy. Surgical modifications and improvements have resulted in excellent seizure outcomes with low operative morbidity and mortality ¹⁾.

Functional Hemispherectomy History.

It is the standard treatment used to cure hemispheric epilepsy syndromes in childhood.

for unilateral seizures with widespread hemispheric lesions and profound contralateral neurologic deficit. If any cortex is left, must make sure it is functionally deafferented (disconnected)

● anatomic hemispherectomy

● functional hemispherectomy: preservation of the basal ganglia isolates the abnormal side with ≈ 80% seizure control rate (similar to anatomic hemispherectomy, but with a lower complication rate).

Various hemispherotomy techniques have been developed to reduce complication rates and achieve the best possible seizure control.

Rasmussen's encephalitis.

FDG PET scan can help decision making in 53% of presurgical patients with normal or discordant MRI. PET findings need to be evaluated in conjunction with other data ²⁾

especially in patients with inconsistent (bilateral) MRI findings ³⁾.

Hemispherotomy for Hemimegalencephaly

Hemispherectomy for Rasmussen's encephalitis.

During most hemispherotomies, the surgeon reaches the lateral ventricle through the frontoparietal opercula or temporal lobe; removes the mesial temporal structures; and disconnects the frontal lobe ahead, the parietal and occipital lobes behind, and the intraventricular fibers of the corpus callosum above the central core. After a temporal lobectomy, the landmarks include the choroid plexus and posterior/ascending portion of the tentorium to disconnect the parietal and occipital lobes, the callosal sulcus or distal anterior cerebral artery (ACA) to sever the intraventricular fibers of the corpus callosum, and the head of the caudate nucleus and ACA to detach the frontal lobe.

These landmarks can be used in any hemispherotomy during which a cerebral hemisphere is disconnected from its lateral surface. Furthermore, they can be used to perform any resection around the central core of the hemisphere and the tentorial incisura ⁴⁾.

Various hemispherotomy techniques have been developed

The transsylvian keyhole procedure has been demonstrated to further reduce operation time and the need for blood replacement. It is most easily performed in cases with enlarged ventricles or perinatal ischemic cysts and is not recommended for hemimegalencephaly. The immediate seizure relief was satisfying. This minimal-exposure approach seems to be a satisfying alternative among possible functional hemispherectomy procedures ⁵⁾.

Lee et al. performed in 50 patients hemispherectomy surgery (mean follow-up time, 3.5 years). Modified lateral hemispherotomy became the preferred technique and was performed on 44 patients. Forty patients (80%) achieved complete seizure freedom (Engel I). Presurgical and postsurgical neuropsychological evaluations demonstrated cognitive stability. Two cases were performed for palliation only. Previous hemispherectomy surgery was associated with worsened seizure outcome (2 of 6 seizure free; P .005). The use of Avitene was associated with a higher incidence of postoperative hydrocephalus (56% vs 18%; P = .03). In modified lateral hemispherotomy patients without the use of Avitene, the incidence of hydrocephalus was 13%. Complications included infection (n = 3), incomplete disconnection requiring reoperation (n = 1), reversible ischemic neurological deficit (n = 1), and craniosynostosis (n = 1). There were no (unanticipated) permanent neurological deficits or deaths. Minor technique modifications were made in response to specific complications.

The modified lateral hemispherotomy is effective and safe for both initial and revision hemispherectomy surgery. Avitene use appears to result in a greater incidence of postoperative hydrocephalus ⁶⁾.

Endoscopy-assisted interhemispheric transcallosal hemispherotomy

The goal of a study was to identify the possible predictors of seizure outcome by pooling the rates of postoperative seizure freedom found in the published literature.

A comprehensive literature search of PubMed, Embase, and the Cochrane Library identified English-language articles published since 1970 that describe seizure outcomes in patients who underwent hemispheric surgery for refractory epilepsy. Two reviewers independently assessed article eligibility and extracted the data. The authors pooled rates of seizure freedom from papers included in the study. Eight potential prognostic variables were identified and dichotomized for analyses. The authors also compared continuous variables within seizure-free and seizure-recurrent groups. Random- or fixed-effects models were used in the analyses depending on the presence or absence of heterogeneity. RESULTS The pooled seizure-free rate among the 1528 patients (from 56 studies) who underwent hemispheric surgery was 73%. Patients with an epilepsy etiology of developmental disorders, generalized seizures, nonlateralization on electroencephalography, and contralateral MRI abnormalities had reduced odds of being seizure-free after surgery.

Hemispheric surgery is an effective therapeutic modality for medically intractable epilepsy. This meta-analysis provides useful evidence-based information for the selection of candidates for hemispheric surgery, presurgical counseling, and explanation of seizure outcomes ⁷⁾.

The clinical record and MRI data of 53 patients were retrospectively analyzed. The correlation between preoperative cerebral peduncle asymmetry ratio (pCPAR) and pre- and postoperative changes in motor function was evaluated, as well as the influence factors of pCPAR, such as duration and etiology factors. The restoration of motor function was defined as changes in pre- and postoperative hemiparesis.

The pCPAR of patients with improved and unchanged hemiparesis were significantly higher than that of worsen patients. Patients with a pCPAR of more than 1.5 had an obvious restorative capacity of motor function of the intact hemisphere, and these patients had a lower risk of worsening hemiparesis. The duration in the improved/unchanged and worsen groups was 5.84 ± 3.85 and 2.67 ± 2.03 years, respectively. Furthermore, there were more patients with non-progressive pathology in the group where pCPAR was more than 1.5.

pCPAR is a useful and objective indicator for predicting the restoration of motor function in pediatric patients with medically intractable epilepsy before hemispherectomy. Most patients with non-progressive pathology and a duration of more than five years presented with higher pCPARs, exhibited better restoration of motor function, and had less risk of worsening hemiparesis ⁸⁾.

Twenty-two patients who underwent hemispherectomy at our institution were retrospectively included. Using iPlan/BrainLAB (BrainLAB, Feldkirchen, Germany) imaging software and a semiautomatic voxel-based segmentation method, we calculated the preoperative cerebral peduncle and cerebellar hemisphere volumes. Cerebral peduncle and cerebellar hemisphere ratios were compared between patients with worsened or unchanged/better hemiparesis postoperatively. RESULTS: The ratios of ipsilateral/contralateral cerebral peduncles (0.570 vs 0.828; P = .02) and contralateral/ipsilateral cerebellar hemispheres (0.885 vs 1.031; P = .009) were significantly lower in patients who had unchanged/improved hemiparesis postoperatively compared with patients who had worsened hemiparesis. Relative risk of worsening hemiparesis was significantly higher in patients with a cerebral peduncle ratio < 0.7 (relative risk, 4.3; P = .03) or a cerebellar ratio < 1.0 (relative risk, 6.4; P = .006).

Although patients who undergo hemispherectomy are heterogeneous, we report a method of predicting postoperative hemiparesis using only standard volumetric magnetic resonance imaging. This information could be used in preoperative discussions with patients and families to help better understand that chance of retaining baseline motor function ⁹⁾.

Forty children who underwent H (23 females, 16 right H) were evaluated at a mean age of 12.8 years (±2.6) with two receptive tasks (oral comprehension and syntactic judgment), the Children's Communication Checklist (CCC) rating scale, and the Behavioral Rating Inventory of Executive Function (BRIEF) questionnaire in order to evaluate the role of executive functions on pragmatic skills. Children operated on before the age of 18 months were considered the “early” group (5 right H and 9 left H), while those operated on later were called the “late” group (11 right H and 15 left H).

The whole group had significant deficits in all three measures. We demonstrated a statistically significant crossed interaction between the side of H and the age at H with pragmatic language disorders (F(1,36)=17.48; p=.0002) and disorders in executive function (F(1,36)=5.80; p=.021) in left early H and in right late H patients. These findings are consistent with the previous studies of pragmatic language disorders concerning adolescents and adults with right hemisphere damage and emphasize the contribution of structural language in the early stage of verbal communication.

These results emphasize for the first time that hemispherotomized children have pragmatic language disorders that are independent of receptive language. The findings are congruent with the recent theory on pragmatic language development in childhood with evidence of a participation of the left hemisphere at the early age followed by right hemispheric specialization and involvement of executive functions, independently of receptive language ¹⁰⁾.

A countrywide Dutch cohort study of 31 patients, who underwent HE between 1994 and 2009, included a semi-structured interview with parents, an assessment of cognition, and screening of behavioral problems and HrQoL.

Twenty-two school-age children and young adults [median age 13.8 years (0.5 at epilepsy onset, 5.3 at HE)] were assessed with age-appropriate cognitive tests. IQ ranged from 45 to 82 (median 61). Despite performing below mean norm scores, these participants could learn and remember, sustain attention, inhibit irrelevant responses, read and write. Nine more children [median age 9.7 years (0.25 at epilepsy onset, 1.4 at HE)] were so mentally retarded that age-appropriate testing was impossible. This group was almost totally dependent on others in daily activities, had the highest proportion of pre-existing contralateral MRI-abnormalities and after HE the highest rates of seizure recurrence and behavioral problems. Parents in both groups rated HrQoL surprisingly positively (mean VAS-score 72.5), with a scarce low rating (40). All parents reported problems with respect to their children's self-care, daily activities and mobility.

At least five years after HE, cognitive, behavioral and daily functioning encompasses a broad spectrum that varies from profound retardation and almost total dependence to low normal cognition and a reasonably independent existence. Pre-existing contralateral MRI abnormalities reflect a more generally affected brain with a limited ability to mediate development after HE ¹¹⁾.

Profuse bleeding originating from an injured cerebral sinus can be a harrowing experience for any surgeon, particularly during an operation on a young child. Common surgical remedies include sinus ligation, primary repair, placement of a hemostatic plug, and patch or venous grafting that may require temporary stenting.

In a paper the Tuite et al., describe the use of a contoured bioresorbable plate to hold a hemostatic plug in place along a tear in the inferomedial portion of a relatively inaccessible part of the posterior segment of the superior sagittal sinus in an 11-kg infant undergoing hemispherotomy for epilepsy. This variation on previously described hemostatic techniques proved to be easy, effective, and ultimately lifesaving. Surgeons may find this technique useful in similar dire circumstances when previously described techniques are ineffective or impractical ¹²⁾.

Preservation of the basal ganglia isolates the abnormal side with ≈ an 80% seizure control rate (similar to anatomic hemispherectomy, but with a lower complication rate).

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. Young et al. summarized 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 ¹³⁾.

In order to avoid the severe complications of anatomical hemispherectomy, technical variations involving hemispherotomy with less resection and more disconnection have been described, such as hemidecortication by Ignelzi and Bucy, ¹⁴⁾ and functional hemispherotomy by Delalande et al. ¹⁵⁾. The principle of functional hemispherotomy is leaving the live, vascularized brain, which is functionally disconnected from the contralateral healthy brain, intact. Hemispherotomy techniques were introduced in the 1990s by Delalande et al., ¹⁶⁾ Villemure and Daniel, ¹⁷⁾ and Schramm et al., ^{18) 19)} each with their own solution to achieving the disconnections required to attain complete functional disconnection of the hemisphere. Cook et al. ²⁰⁾ described a modified lateral hemispherotomy, which involves sacrifice of the middle cerebral artery with removal of a central block of opercular tissue. Bahuleyan et al.13 demonstrated the feasibility of a purely endoscopic transventricular hemispherectomy on cadaver brains as proof of concept. Hemispherotomy techniques involving partial cortical removal, which allow for the functional isolation of the hemisphere affected by severe epilepsy with excellent results, are continually being refined and have become predominant at most epilepsy centers in the 21st century ²¹⁾.

Peri-insular hemispherotomy