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 »  Abstract
 » Objective
 » Case Study
 » Surgical Plan
 » Surgical Technique
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Table of Contents    
VIDEO SECTION-OPERATIVE NUANCES: STEP BY STEP
Year : 2021  |  Volume : 69  |  Issue : 4  |  Page : 837-841

Endoscopic Hemispherotomy for Nonatrophic Rasmussen's Encephalopathy


1 Department of Neurosurgery, All India Institute of Medical Sciences (AIIMS), New Delhi, India
2 Department of Neurology, All India Institute of Medical Sciences (AIIMS), New Delhi, India
3 Department of Nuclear Medicine, All India Institute of Medical Sciences (AIIMS), New Delhi, India
4 Department of Neuroradiology, All India Institute of Medical Sciences (AIIMS), New Delhi, India

Date of Submission12-Aug-2021
Date of Decision13-Aug-2021
Date of Acceptance13-Aug-2021
Date of Web Publication2-Sep-2021

Correspondence Address:
Dr. P Sarat Chandra
Department of Neurosurgery, Professor and Head of Unit 1, All India Institute of Medical Sciences (AIIMS), New Delhi - 110 029
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0028-3886.325379

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 » Abstract 


Background: Hemispheric disconnection represents a challenging and major epilepsy surgical procedure. This procedure in experienced hands offers excellent results in terms of seizure outcomes, especially for hemispheric pathologies such as Rasmussen's encephalitis, hemispheric dysplasias, hemimegalencephaly. The technique of hemispherotomy has witnessed various modifications over the years, beginning from anatomical hemispherectomy to the current era of minimally invasive functional hemispheric disconnections.
Objective: This study aimed to describe the technique of performing endoscopic vertical hemispherotomy using interhemispheric corridor developed by the senior author.
Materials and Methods: A 12-year-old girl with seizure onset at the age of 10 years presented with an aura of fear and nausea followed by tonic deviation of eyes to the right and blinking with speech arrest. There were tonic–clonic movements of the right-sided limbs along with ictal spitting and occasional deviation of the angle of mouth to the right. The patient had loss of awareness for the event along with postictal confusion lasting few minutes.
Results: Video electroencephalography (VEEG) revealed left parietocentral and left temporal localization. Serial magnetic resonance imaging (MRI) brain over 3 years revealed progressive left hemispheric changes suggestive of Rasmussen's encephalitis. The patient underwent left-sided endoscopic hemispherotomy. At 2 years follow-up, the patient is seizure-free (ILAE [International League Against Epilepsy] Class 1).
Conclusion: Endoscopic hemispherotomy using the interhemispheric approach is an elegant, minimally invasive, reproducible, safe, and efficacious technique.


Keywords: Hemispheric disconnection, interhemispheric approach, minimally invasive epilepsy surgery, vertical hemispherotomy
Key Message: Endoscopic hemispherotomy is a minimally invasive technique associated with minimal blood loss and shorter hospital stay with comparable results to the classical open techniques. This technique entails precise knowledge of anatomy and demands a steep learning curve.


How to cite this article:
Doddamani RS, Chandra P S, Samala R, Ramanujan B, Tripathi M, Bal C S, Garg A, Gaikwad S, Tripathi M. Endoscopic Hemispherotomy for Nonatrophic Rasmussen's Encephalopathy. Neurol India 2021;69:837-41

How to cite this URL:
Doddamani RS, Chandra P S, Samala R, Ramanujan B, Tripathi M, Bal C S, Garg A, Gaikwad S, Tripathi M. Endoscopic Hemispherotomy for Nonatrophic Rasmussen's Encephalopathy. Neurol India [serial online] 2021 [cited 2021 Oct 22];69:837-41. Available from: https://www.neurologyindia.com/text.asp?2021/69/4/837/325379




Hemispherotomy (HS) is the procedure of choice for unihemispheric drug-refractory epilepsy. The HS techniques broadly fall into two basic categories: lateral and vertical approaches.[1] These approaches have undergone various modifications over the years. The technique of endoscopic hemispherotomy (EHS) is the latest advancement, pioneered by the senior author (PSC).[2] Majority of the patients requiring HS are children, and thus minimal access surgeries are advantageous in terms of minimizing the blood loss and morbidity compared with the open methods.[3],[4] The endoscopic technique has the advantage of magnification and panoramic and angled visualization.[4]


 » Objective Top


This study aimed to describe the technique of performing vertical EHS using interhemispheric corridor and its pearls and pitfalls.


 » Case Study Top


A 12-year-old right-handed girl with seizure onset at the age of 10 years presented with an aura of fear and nausea followed by tonic deviation of the eyes to the right and blinking with speech arrest. There were tonic–clonic movements of the right-sided limbs along with ictal spitting and deviation of the angle of mouth to the right occasionally. Over the period of the past 2 years, she started to develop continuous involuntary tonic–clonic movements involving the right upper limb suggestive of epilepsia partialis continua (EPC). The patient had a loss of awareness for the event along with postictal confusion lasting few minutes. Examination revealed right-sided hemiparesis (MRC [Medical Research Council] Grade 2/5) and loss of pincer grasp along with continuous movements involving the right hand.

Video electroencephalography (VEEG) revealed left parietocentral and left temporal localization. Magnetic resonance imaging (MRI) brain revealed widened sulci on the left side, predominantly involving the peri-Sylvian region. There is associated left lateral ventricular enlargement along with hyperintensity of the left extreme capsule on the fluid-attenuated inversion recovery (FLAIR) images. These changes were progressive as compared with the MRI performed 3 years prior and were suggestive of Rasmussen's encephalitis (RE). The patient was also investigated with ictal SPECT (single-photon emission computed tomography), magnetoencephalography, and fMRI (functional MRI) for language and memory (see video). Following this, the patient underwent left-sided EHS. At 2 years follow-up, the patient is seizure-free (ILAE [International League Against Epilepsy] Class 1). The histopathology confirmed the radiological diagnosis.


 » Surgical Plan Top


In view of refractory epilepsy along with progressive hemispheric changes on the left side, as seen on serial brain imaging, a diagnosis of RE was considered. Hence, the patient was counseled and planned for left-sided EHS.


 » Surgical Technique Top


The technique of EHS using interhemispheric corridor was described for the first time in the literature from our institution by the senior author (PSC). The following are special requirements used in our technique:

  1. A 30-cm long, 1-cm wide, zero-degree endoscope (Karl Storz, Tuttlingen, Germany)
  2. Endoscope holder (robotic arm in our technique)
  3. Long-shafted suction catheters
  4. Variable impedance bipolar forceps; Sutter Medizintechnik or Vesalius bipolar systems (Medilife Technologies, New Delhi, India)
  5. Neuronavigation (Medtronic StealthStation S7)


The technique of EHS is divided into four steps as follows:

  1. Corpus callosotomy (using interhemispheric corridor)
  2. Anterior disconnection: This is performed from genu along the coronal plane, reaching the base of the frontal lobe and going till the lateral part of the beginning in the extraventricular region just anterior to the ventricle. This is to prevent any damage to the hypothalamic nuclei around the anterior perforated substance
  3. Middle disconnection (connecting the lateral ventricle to the temporal horn and includes the resection of the amygdala, hippocampus)
  4. Posterior disconnection (splenial and fornicial disconnection)


Video Link: https://youtu.be/F16eBwCQxjg

QR code: ???

Video timeline

0:12–0:15 – This video demonstrates the technique of performing vertical EHS using interhemispheric corridor.

0:15–1:01 – A 12-year-old right-handed girl with seizure onset at the age of 10 years had a frequency of 15 to 20 seizures/day. She presented with an aura of fear and nausea followed by tonic deviation of eyes to the right and blinking with speech arrest. There were tonic–clonic movements of the right-sided limbs along with ictal spitting and occasional deviation of the angle of mouth to the right associated with loss of awareness. Over the period of the past 2 years, she started to have EPC involving the right hand. Examination revealed right-sided hemiparesis and loss of pincer grasp. The VEEG revealed left parieto central and left temporal localization

1:01–1:08 – Received methylprednisolone with transient benefit considering the diagnosis of RE

1: 08–1:14 – She was on multiple antiepileptic drugs without benefit in seizure freedom

1:14–1:23 – Neuropsychological assessment revealed global impairment including visual and verbal memory functions

1:23–1:57 – MRI brain revealed widened sulci on the left side predominantly involving the peri-Sylvian region. There is associated left lateral ventricular enlargement along with hyperintensity of the left extreme capsule on FLAIR images. Similar findings were noted on T1 weighted imaging. These changes were progressive as compared with the MRI performed 3 years before.

1:57–2:10 – SPECT and positron emission tomography localized to the left frontal and left frontotemporal hypometabolism, respectively.

2:10–2:30 – fMRI revealed good representation of the left-hand area over the right pre- and postcentral gyri. Speech, language, and memory showed BOLD (blood-oxygen-level dependent) activation localized bilaterally to both the lobes.

2:30–2:40 – The endoscopic approach provides an inverse funnel–shaped expanded panoramic view.

2:40–3:10 – Under general anesthesia, the patient's head is fixed with slight neck flexion (15°–20°). A 5-cm transverse incision 1 cm anterior to the coronal suture is given followed by a 3 × 2.5 cm semicircular craniotomy fashioned with the base toward the midline and apex laterally [Figure 1].
Figure 1: (a and b) Approximately 5 cm incision parallel and 1 cm anterior to the coronal suture is marked. A 3 × 4 cm small semicircular craniotomy is fashioned, with the base toward the midline

Click here to view


3:10–3:21 – After opening the dura, the endoscope is brought into the field and the interhemispheric fissure is opened meticulously using sharp dissection.

3:21–3:47 – The cingulate gyrus adhesions as seen in this case should be released so as to reach the corpus callosum. Recognizing the pearly white corpus callosum along with the callosomarginal and pericallosal arteries is crucial prior to the beginning of callosotomy.

5:02–5:27 – The exposure of the corpus callosum is continued from the body till genu, where both the A2 anterior cerebral arteries dip inferiorly. At this stage, a roll of “spongastan” (gelfoam) is placed along the genu, which facilitates atraumatic dissection by expansion owing to its hygroscopic nature.

5:27–6:05 – The exposure of the corpus callosum is then continued posteriorly till the splenium. Once complete, the callosal sectioning is commenced. It is crucial to maintain the callosotomy ipsilateral to the side of HS in order to enter the ipsilateral lateral ventricle.

The corpus callosum is then continued anteriorly till the genu maintaining the same plane till the ipsilateral frontal horn. It is important to preserve the anterior commissure during this procedure.

6:14–6:48 – The anterior disconnection is commenced; we prefer to perform this step extraventricular anterior to the frontal horn with the use of navigation guides during this step. The basal arachnoid after resecting the gyrus rectus is exposed, and the line of disconnection is then carried out lateral to the head of the caudate nucleus. Exposure of the basifrontal arachnoid ensures the completeness of the anterior disconnection. Care should be taken to preserve the olfactory tract subpially [Figure 2].
Figure 2: (a) Interhemispheric fissure opening and cingulate adhesiolysis; (b and c) Both A2 anterior cerebral arteries are exposed along with corpus callosum, (d) Callosotomy ipsilateral to the side of hemispherotomy, (e) Anterior disconnection (white dotted curved line) following callosotomy

Click here to view


7:04–7:20 – The goal of middle disconnection is to connect the lateral ventricles to the temporal horn. The choroid plexus of the temporal horn serves as an important landmark at this stage.

7:20–7:45 – Once the temporal horn is exposed, the amygdala and the hippocampal head are resected. During the middle disconnection stage, bleeding is encountered from the lenticulostriate and the thalomostriate perforators. Therefore, the use of variable impedance bipolar coagulation forceps at higher coagulation settings is very useful. It is also important to disconnect the temporal stem anterior to the hippocampal head.

7:53–8:05 – The middle disconnection is continued till the Sylvian arachnoid as the inferior most limit with sphenoid ridge transition of the anterior to the middle cranial fossa serving as a fixed landmark.

8:21–8:33 – The middle disconnection is carried out posteriorly lateral to the thalamus following the temporal choroid plexus till the atrium of the lateral ventricle is reached.

8:51–9:28 – Once the middle disconnection is complete, the posterior disconnection is performed, which consists of a splenial disconnection. It is vital to carefully disconnect the thick bundle of the splenial fibers till the arachnoid of the quadrigeminal cistern is visible. This is followed by the forniceal disconnection, which completes the hemispheric disconnection [Figure 3].
Figure 3: (a) Middle disconnection depicted by the dotted line, which should be lateral to the thalamus. (b) Connecting lateral ventricle to the temporal horn choroid plexus (white star) serves as a landmark, (c) Completed anterior and middle disconnection along the choroidal fissure (white dotted curved line), (d) Splenial disconnection and the quadrigeminal arachnoid are seen

Click here to view


Therefore, hemispheric disconnection preserves the diencephalic structures, which are left intact and connected to the normal hemisphere, while the rest of the affected hemisphere is isolated.

9:31–9:49 – Once the disconnective procedure is completed, thorough irrigation of the operative cavity with warm saline to adequately evacuate the blood products is performed. This might be later responsible for the prolonged postoperative fever in some of the patients.

9:50–10:10 – The cortical/subcortical tissue biopsy is performed for histopathological confirmation of the diagnosis. This is followed by watertight dural closure and replacement of the bone flap and wound closure in a standard fashion. A drain is placed and kept for 72 hours to allow the drainage of blood mixed with cerebrospinal fluid if any.

10:10–10:16 – Postoperative MRI showed good hemispheric disconnection.

10: 16–10: 21 – The patient is seizure-free at 1-year follow-up.

Outcomes

The postoperative course was uneventful. The patient developed hemiplegia immediately following surgery. There was no language deficit. The patient is seizure-free (ILAE Class 1) at 1 year follow-up. The weakness improved from Grade 0/5 to Grade 3–4/5 at 1 year follow-up. The patient was able to walk without support. The resected specimen of the cortical/subcortical tissue confirmed RE on histopathology.

Pearls and pitfalls

  • Patient selection is critical for a successful outcome. Comprehensive evaluation maximizing the noninvasive multimodality investigations and formulating a hypothesis is essential.
  • Thorough anatomical perspective is of paramount importance, and the operating surgeon should be cognizant.
  • The use of navigation assists in choosing an appropriate site free of bridging veins for placing the craniotomy.
  • Use of long shaft suction catheter and bipolar coagulation forceps, especially of variable impedance bipolar, is recommended.
  • Cingulate adhesion should be released with sharp dissection; otherwise, misinterpretation of the cingulate as corpus callosum is quite possible in the presence of callosomarginal arteries that may add to the confusion.
  • Corpus callosum is a pearly white structure with bilateral pericallosal arteries coursing over it.
  • It is vital to perform callosotomy ipsilateral to the side of HS, so as to enter into the ipsilateral lateral ventricle.
  • The anterior disconnection should begin extraventricularly to avoid entering into the basal nuclei and the hypothalamic nuclei.
  • The middle disconnection connects the lateral ventricle to the temporal horn.
  • Some bleeding is usually encountered in the middle disconnection, and hence high coagulation settings should be preferred during this step.
  • The temporal stem (TS) may be missed with this approach owing to the depth and the direction of the dissection, which is lateral, while the TS is medial. The use of angled (30° endoscope) and lighted suction may be very useful to avoid skipping this structure. It is also important to counsel the patient for a possible staging if complete disconnection cannot be performed in the first sitting. This may be true for nonatrophic pathologies such as the current case and also hemimegalencephaly.
  • Choroid plexus serves as a constant and key landmark for successful completion of the hemispheric disconnection.
  • The splenial fibers should be disconnected, and the completeness of this disconnection is ascertained by the visualization of the arachnoid of the quadrigeminal cistern.
  • Fornicial disconnection completes the posterior disconnection.
  • The aim of HS is the preservation of the diencephalic structures, which remain intact and connected to the normal hemisphere, while disconnecting the abnormal hemisphere.
  • Thorough irrigation of the operative cavity with warm saline to remove the blood products is vital to avoid prolonged postoperative fever. Leaving a drain for 48 to 72 hours is also advisable. This may reduce the incidence of hydrocephalus.



 » Discussion Top


Hemispheric disconnection techniques have evolved with time from hitherto large craniotomies with anatomical hemispherectomy to the current era of minimally invasive epilepsy surgery.[2],[3],[4],[5],[6] The EHS technique, developed at our institution, is a minimally invasive solution disconnecting the entire hemisphere through a keyhole approach.[2] This technique is associated with minimal blood loss, lesser operative time, hospital stay, and equivalent efficacy in terms of seizure freedom, compared with the open techniques.[4] The existence of residual connection owing to the missed TS is a frequent cause of failed HS with this technique, as noted in our series previously.[7]


 » Conclusion Top


EHS is a minimally invasive, safe, and efficacious technique and can be performed even in very young children with minimal blood loss and morbidity compared with the open techniques with large craniotomies.

Declaration of patient consent

Full and detailed consent from the patient/guardian has been taken. The patient's identity has been adequately anonymized. If anything related to the patient's identity is shown, adequate consent has been taken from the patient/relative/guardian. The journal will not be responsible for any medicolegal issues arising out of the issues related to the patient's identity or any other issues arising from the public display of the video.

Financial support and sponsorship

This study has been partly funded by the MEG resource facility funded by the Department of Biotechnology, Ministry of Science and Technology.

Conflicts of interest

There are no conflicts of interest.



 
 » References Top

1.
Baumgartner JE, Blount JP, Blauwblomme T, Chandra PS. Technical descriptions of four hemispherectomy approaches: From the pediatric epilepsy surgery meeting at Gothenburg 2014. Epilepsia 2017;58(Suppl 1):46-55.  Back to cited text no. 1
    
2.
Chandra PS, Kurwale N, Garg A, Dwivedi R, Malviya SV, Tripathi M. Endoscopy-assisted interhemispheric transcallosal hemispherotomy: Preliminary description of a novel technique. Neurosurgery 2015;76:485-95.  Back to cited text no. 2
    
3.
Chandra PS, Subianto H, Bajaj J, Girishan S, Doddamani R, Ramanujam B, et al. 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. J Neurosurg Pediatr 2019;23:187-97.  Back to cited text no. 3
    
4.
Chandra SP, Tripathi M. Endoscopic epilepsy surgery: Emergence of a new procedure. Neurol India 2015;63:571-82.  Back to cited text no. 4
[PUBMED]  [Full text]  
5.
Chandra PS, Doddamani R, Girishan S, Samala R, Agrawal M, Garg A, et al. Robotic thermocoagulative hemispherotomy: Concept, feasibility, outcomes, and safety of a new “bloodless” technique. J Neurosurg Pediatr 2021;1-12. doi: 10.3171/2020.10.PEDS20673. Online ahead of print.  Back to cited text no. 5
    
6.
Dwivedi R, Ramanujan B, Chandra PS, Sapra S, Gulati S, Kalaivani M, et al. Surgery for drug-resistant epilepsy in children. N Engl J Med 2017;377:1639-47.  Back to cited text no. 6
    
7.
Girishan S, Tripathi M, Garg A, Doddamani R, Bajaj J, Ramanujam B, et al. Enhancing outcomes of endoscopic vertical approach hemispherotomy: Understanding the role of “temporal stem” residual connections causing recurrence of seizures. J Neurosurg Pediatr 2020;25:159-167.  Back to cited text no. 7
    


    Figures

  [Figure 1], [Figure 2], [Figure 3]



 

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