Endoscopic Hemispherotomy for Nonatrophic Rasmussen's Encephalopathy
Correspondence Address: Source of Support: None, Conflict of Interest: None DOI: 10.4103/0028-3886.325379
Source of Support: None, Conflict of Interest: None
Keywords: Hemispheric disconnection, interhemispheric approach, minimally invasive epilepsy surgery, vertical hemispherotomyKey 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.
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. 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). 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., The endoscopic technique has the advantage of magnification and panoramic and angled visualization.
This study aimed to describe the technique of performing vertical EHS using interhemispheric corridor and its pearls and pitfalls.
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.
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.
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:
The technique of EHS is divided into four steps as follows:
Video Link: https://youtu.be/F16eBwCQxjg
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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].
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].
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].
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.
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
Hemispheric disconnection techniques have evolved with time from hitherto large craniotomies with anatomical hemispherectomy to the current era of minimally invasive epilepsy surgery.,,,, The EHS technique, developed at our institution, is a minimally invasive solution disconnecting the entire hemisphere through a keyhole approach. 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. 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.
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.
[Figure 1], [Figure 2], [Figure 3]