Endoscope-assisted (with robotic guidance and using a hybrid technique) interhemispheric transcallosal hemispherotomy: a comparative study with open hemispherotomy to evaluate efficacy, complications, and outcome

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OBJECTIVE

Endoscope-assisted hemispherotomy (EH) has emerged as a good alternative option for hemispheric pathologies with drug-resistant epilepsy.

METHODS

This was a prospective observational study. Parameters measured included primary outcome measures (frequency, severity of seizures) and secondary outcomes (cognition, behavior, and quality of life). Blood loss, operating time, complications, and hospital stay were also taken into account. A comparison was made between the open hemispherotomy (OH) and endoscopic techniques performed by the senior author.

RESULTS

Of 59 cases (42 males), 27 underwent OH (8 periinsular, the rest vertical) and 32 received EH. The mean age was 8.65 ± 5.41 years (EH: 8.6 ± 5.3 years; OH: 8.6 ± 5.7 years). Seizure frequency per day was 7 ± 5.9 (EH: 7.3 ± 4.6; OH: 15.0 ± 6.2). Duration of disease (years since first episode) was 3.92 ± 1.24 years (EH: 5.2 ± 4.3; OH: 5.8 ± 4.5 years). Number of antiepileptic drugs per patient was 3.9 ± 1.2 (EH: 4.2 ± 1.2; OH: 3.8 ± 0.98). Values for the foregoing variables are expressed as the mean ± SD. Pathologies included the following: postinfarct encephalomalacia in 19 (EH: 11); Rasmussen’s syndrome in 14 (EH: 7); hemimegalencephaly in 12 (EH: 7); hemispheric cortical dysplasia in 7 (EH: 4); postencephalitis sequelae in 6 (EH: 2); and Sturge-Weber syndrome in 1 (EH: 1). The mean follow-up was 40.16 ± 17.3 months. Thirty-nine of 49 (79.6%) had favorable outcomes (International League Against Epilepsy class I and II): in EH the total was 19/23 (82.6%) and in OH it was 20/26 (76.9%). There was no difference in the primary outcome between EH and OH (p = 0.15). Significant improvement was seen in the behavioral/quality of life performance, but not in IQ scores in both EH and OH (p < 0.01, no intergroup difference). Blood loss (p = 0.02) and hospital stay (p = 0.049) were less in EH.

CONCLUSIONS

EH was as effective as the open procedure in terms of primary and secondary outcomes. It also resulted in less blood loss and a shorter postoperative hospital stay.

ABBREVIATIONS AED = antiepileptic drug; CBCL = Child Behavior Checklist; EEG = electroencephalography; EH = endoscope-assisted hemispherotomy; HASS = Hague seizure severity; ILAE = International League Against Epilepsy; OH = open hemispherotomy; PedsQL = Pediatric Quality of Life; QOL = quality of life.

Article Information

Correspondence P. Sarat Chandra: All India Institute of Medical Sciences, New Delhi, India. saratpchandra3@gmail.com.

INCLUDE WHEN CITING Published online November 9, 2018; DOI: 10.3171/2018.8.PEDS18131.

Disclosures The authors report no conflict of interest concerning the materials or methods used in this study or the findings specified in this paper.

© AANS, except where prohibited by US copyright law.

Headings

Figures

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    Photographs showing the operative steps of EH. A: The size of skin incision, which was approximately 5 cm along the coronal plane. All photographs except panel A were taken from the endoscope (the usual ring is not seen because the view is magnified). The skin incision was placed anterior to the coronal suture, and the exact site was decided by neuronavigation to avoid bridging veins. The bone flap was 4 × 3 cm (sagittal × coronal) and is raised on one side of the midline. B and C: The dura was opened in a C-shaped manner with the base toward the midline. D: The brain may look full initially. However, gentle retraction of the hemisphere followed by gradual and patient release of CSF will lead to the brain becoming lax, and the interhemispheric fissure opens up like a book. It is also important to understand that the procedure follows the principles of keyhole surgery, in which there is more retraction in the deeper part than on the surface (expanding cone). F = falx. E: The corpus callosum (cc) is gently exposed from the genu toward the posterior part between both of the anterior cerebral arteries (ACAs). F: The corpus callosum is then divided; first the posterior part, followed by the splenium (which is curving inferiorly and hence can be divided once the posterior part is divided), and then finally followed by genu. It is important to split the corpus callosum so that the ipsilateral ventricle is entered (Cp = choroid plexus). G: The junction of the genu and the ACA is then exposed. H: The anterior disconnection (AD) is then started at the junction of the ACA and genu anterior to the ventricle. This disconnection is now extended laterally along the coronal plane, anterior to the head of the caudate nucleus (Ca). I: The anterior disconnection is then deepened inferiorly until the posterior part of the anterior cranial fossa is reached. It is extended laterally until the lateral part of the head of caudate nucleus is reached. J: The middle disconnection is now started at the lateralmost part of the anterior disconnection and passes lateral to the putamen and thalamus (Th). K: Progress of the middle disconnection, which is deepened and exposes the sphenoid ridge and the middle cerebral artery anteriorly and opens into the temporal horn posteriorly. L: Both the amygdala (Am) and the hippocampus (Hipp) can be seen in this figure. M: The choroid plexus along the choroid fissure as it passes to the temporal horn (as it is seen after the middle disconnection) is completed lateral to the thalamus. N: Following the middle disconnection, the next important step is to aspirate the ventral amygdala and the anterior part of hippocampus so that it is disconnected from the dorsal amygdala, effectively disconnecting the anterior medial part of the temporal lobe from the diencephalic structures. O: The last part of the hemispheric disconnection is the posterior disconnection (PD), which passes along the line connecting the splenium (Sp) laterally and the choroid plexus medially. P: This technique disconnects the temporal efferents consisting of the tail of the hippocampus and the fornix. Figure is available in color online only.

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    The operating room setup of the endoscope with the robotic device. It is important for the surgeon to be seated comfortably so that an optimal visual axis (A) is maintained along with proper back support (B). It is also important to have proper elbow support (C). The endoscope (D) uses a hybrid technique as described in the text. Proper ergonomics are important to enhance accuracy of the surgery and prevent surgeon exhaustion. Figure is available in color online only.

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    The fundamental differences between an exoscope, endoscope-assisted surgery, and the hybrid technique proposed by us. While using an exoscope, the telescope is outside the cranial opening, and this leads to dissipation of the light, which may result in inadequate visualization in the depth. In endoscope-assisted surgery, the endoscope (4–5 mm) has to be kept close to the target. This may lead to frequent opacification of the lens because of blood. This system nevertheless provides high magnification, but leads to loss of a bird’s-eye view of the target. Endoscope-assisted surgery may be suitable for pituitary tumors, where the target is approximately 10–15 mm in size. In hemispherotomy, the target is several centimeters in size (from genu to splenium), and thus requires frequent changes of view from a bird’s-eye to a close-up view. To circumvent these problems, we have introduced the concept of a hybrid technique, in which a 10-mm-thick, 310-mm-long scope is used. Although the scope is inside the cranial opening, it is still away from the target. The working instruments such as the suction and bipolar forceps would be distal to the telescope. With the increased thickness of the scope, the visualization becomes better, and the target and the surrounding areas may be visualized easily by changing the magnification. The main advantages of this system are as follows: 1) it allows very good visualization of the target without any diffusion of light extracranially; 2) it does not impede the working of the instruments because the telescope is proximal to them, thus preventing frequent opacification of the lens by blood; and 3) by altering the zoom, the surgeon can rapidly change from magnified view to a bird’s-eye view. Thus, the hybrid system has the advantages of the endoscope and exoscope while avoiding the disadvantages of both.

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    Schematic diagram with embedded labels showing the anterior disconnection (1), middle disconnection (2), excision of the ventral amygdala (3), and the posterior disconnection (4). The diagram is self-explanatory and follows the surgical steps as shown in Fig. 1. Nu. = nucleus. Copyright Mahendra Singh Chouhan. Published with permission. Figure is available in color online only.

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    A 9-year-old girl presenting with progressive increasing severity and frequency of focal seizure (1–3 times/day at the time of surgery) with delayed milestones and with right epilepsia partialis continua. A: MRI sequences showed signal changes in the left hemisphere suggestive of Rasmussen’s syndrome (example of a nonatrophic pathology). B: Following EH performed using neuronavigation she had an ILAE class IA outcome. This MRI sequence was performed 7 days after surgery and shows the line of disconnection in axial (A and B) and coronal (A1 and B1) sections.

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    A 3-year-old boy with Rasmussen’s syndrome (A) who underwent EH. Repeat MRI sequence (B) performed at 1 year showed a deafferentation atrophy of the hemisphere. Arrow indicates the line of middle disconnection between the putamen and thalamus.

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    A 9-month-old boy who had right hemimegalencephaly (A). Following EH, the child had an ILAE class IA outcome at 1 year. However, the repeat MRI showed a persistent connection (arrow) at the level of the ventral amygdala (B). One may also notice a large cavity at the site of disconnection. It is likely that this bridge of tissue is nonfunctional. The child is being followed carefully. In the case of recurrence of seizures, an endoscopic approach may be undertaken to divide this bridge of tissue. This case illustrates the importance of adequate removal of the ventral amygdala and the anterior hippocampus to disconnect the anterior and mesial temporal structures completely from the midline structures.

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    Kaplan-Meier curves for the cumulative survival in relation to seizure events in the OH group (blue line) and EH group (green line). The x-axis is the number of months after the surgery, and the y-axis shows cumulative survival (i.e., patients without a single seizure after the surgery). Censored values (+) indicate the last known follow-up time. Differences between the 2 groups were not significant based on the log-rank test (p = 0.15). Using Fisher’s exact test, the p value was 0.451 at 12 months and 0.371 at 30 months; neither was significant. Figure is available in color online only.

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