Trans-Sylvian Resection of Giant Left Insular Glioma: Operative Technique and Nuances
Correspondence Address: Source of Support: None, Conflict of Interest: None DOI: 10.4103/0028-3886.333450
Source of Support: None, Conflict of Interest: None
Keywords: Bubbling, charring, compartmental resection, image guidance/neuronavigation, insular glioma, neuromonitoring, subcortical mapping
Insula in Latin connotes island, and J. C. Reil, a German neurologist, aptly coined the term “island of Reil” for this region. It is often referred to as the fifth lobe of the brain which lies deep to the lateral sulcus (Sylvian fissure), surrounded by eloquent white matter tracts and basal ganglia structures. Insula is divided into anterior and posterior parts, with the anterior portion housing three short gyri separated by a prominent sulcus from two long gyri in the posterior part [Figure 1].,
Insula is fed by M2 and M3 segments of the middle cerebral artery (MCA) through its perforating vessels, and venous drainage takes place via the deep middle cerebral veins. Short perforators can be safely coagulated and cut during subpial resection, but long perforating branches travel posteriorly and superiorly on the insula and supply the corona radiata and hence must be preserved to avoid ischemic injury resulting in hemiparesis. The lateral lenticulostriate (LLA) perforators (1–15) arise from the M1-MCA segment. Early identification of the LLA is the key landmark, which marks the medial most limit of insular resection. Transgression beyond the LLAs would lead to direct insult to the basal nuclei and the internal capsule, whereas injury to these perforators would lead to the ischemic insult to the internal capsule and dense hemiplegia,,,, [Figure 2].
Insular gliomas are challenging because of their complex anatomy, functional significance, and intimate relationship with the internal carotid artery (ICA), MCA, and LLA. The Berger–Sanai classification system [Figure 3] was therefore introduced, dividing the insular cortex into quadrants (four zones) based on the Sylvian fissure and foramen of Monro planes.,, Zone 1 (anterosuperior) constitutes the most common site of insular gliomas (35%), whereas zone 2 (posterosuperior), zone 3 (inferoposterior), and zone 4 (inferoanterior) tumors represented 6% of cases each, while multiple zones were involved in the remaining patients.,,,
This article is aimed at describing the operative technique step by step by using a trans-Sylvian corridor and performing compartmental dissection and highlighting the operative nuances involved in low-grade gliomas by using intraoperative neuromonitoring and image guidance.
A 32-year-old right-handed gentleman doctor by profession presented to us with the symptoms for the last 8 months in the form of episodes of excessive salivation and tingling sensation on the right side of the body along with nausea. The frequency of these episodes was 2–3 times/day and lasted for 15–20 s. He also developed one episode of speech arrest without any loss of consciousness or abnormal body movement. There were no associated comorbidities. He was started on appropriate antiepileptic medication. On examination, there were no significant deficits. Magnetic resonance imaging (MRI) of the brain revealed left insular lesion with heterogenous contrast enhancement along with predominant nonenhancing areas and patchy restriction on diffusion-weighted imaging (DWI) with moderate perilesional edema [Figure 4]. The patient was planned for tumor removal following appropriate consent.
The surgery was planned under general anesthesia using pterional craniotomy and the trans-Sylvian approach. The tumor removal was accomplished using sequential compartmental decompression in a systematic way based on the Berger–Sinai zones. The following special equipment were utilized in our technique:
The technique of compartmental dissection using the trans-Sylvian approach is divided into the following steps:
Video link: https://youtu.be/xYpqWLE6xoo
Video timeline with audio transcript
0:00–0:45: This video demonstrates the technique of performing compartmental dissection of a giant left insular glioma by using the trans-Sylvian approach.
A 32-year-old right-handed gentleman, a practicing physician by profession, presented to our institution with episodes of excessive salivation, nausea, and tingling on the right half of the body for a duration of 8 months. These episodes lasted for 15–20 s occurring 2–3 times a day.
He suffered one episode of speech arrest associated with a loss of awareness of his surroundings.
Examination revealed no sensory-motor deficits. He was started on appropriate antiepileptic drugs.
00:44–00:55: Insular gliomas are divided into four zones as per the Berger–Sinai classification system by the Sylvian fissure and the foramen of Monroe lines.
00:55–1.18: Contrast MRI of the brain revealed predominantly nonenhancing left insular space-occupying lesion with heterogenous patchy enhancement. On T2 weighted imaging, the lesion was hyperintense and involved all four zones, representing giant insular glioma.
1.18–1.28: Under general anesthesia, the patient's head was fixed with a Mayfield clamp with a 30-degree rotation in the supine position. Pterional craniotomy was performed and the dura was opened in a semicircular fashion.
1.29–01:36: The Sylvian fissure was widely opened in a standard fashion to expose the insular region.
2.19–2.45: Biopsy of the insular lesion is performed. Using bipolar and suction as dynamic retractors sequential compartmental resection as per the Berger–Sinai zones is commenced beginning with the anterior compartment. It can be seen that no retractors are used and only dynamic retraction with the help of bipolar and suction is being utilized.
2:56–3:09: The tumor is coagulated and sucked out using high bipolar coagulation settings along with a standard suction. It is important to note that the tumor tissue bubbles on coagulation owing to its high-water content.
03:30–03:39: The resection is performed by creating windows between the M3-MCA branches and posterior compartmental resection is continued
03:55–04:12: The use of image guidance serves as an important guide during surgery and prevents the surgeon from inadvertently going beyond the limits of the tumor. Thus, it should be used whenever in doubt, even though its accuracy is compromised by the brain shift.
04:13–04:34: Coagulation of the tumor followed by suction decompression is a very useful technique, especially for gliomas. The use of intraoperative cortical and subcortical mapping by using the suction monitoring probe acts as a valuable tool leading to optimal resection and at the same time preventing major motor deficits.
04:34–04:39: The resection is continued posterosuperiorly and then superiorly.
04:50–04:59: It is important to remember that the bubbling tissue represents the tumor tissue, which gives confidence to the surgeon for further resection.
5:00–5:32: The medial limit of the tumor should be meticulously perceived as it is bounded by the internal capsule and the basal ganglia. The lateral lenticulostriate arteries arising from the M1-MCA segment course anteriorly toward the basal ganglia. These perforators are vital and form an important landmark for limiting further medial resection. The cut nutmeg appearance suggests the beginning of the caudate nucleus. These landmarks should always be looked for during the medial resection.
05:34–05:43: The normal white matter chars on coagulation and is identified by the petechial hemorrhages that develop on suctioning.
5:52–06:12: Postoperative recovery was uneventful and the patient remained symptom-free. Histopathology revealed anaplastic oligodendroglioma. MRI performed at 1-month follow-up revealed near-total resection of the tumor. The patient was advised chemoradiotherapy in view of high-grade glioma.
This patient was operated in two sittings as it was a giant insular glioma. Following the second surgery, the patient's recovery was uneventful without any speech difficulty and motor or sensory deficits in the postop period as well as at follow-up after 1 month. A follow-up MRI of the brain showed a good resection of the tumor [Figure 7]. Histopathology confirmed the diagnosis of anaplastic oligodendroglioma (WHO grade 3). Therefore, the patient was advised to undergo chemoradiotherapy.
Pearls and pitfalls
Recent cadaveric studies showed that for tumors in the anterior insula (zones 1 and 4), the transsylvian approach provides sufficient exposure.,,,,,,,,, Resection of these tumors is feasible, relatively safe, and with a significant impact on patient outcomes.
The resection of insular gliomas has been refined in recent times with a better understanding of the microsurgical anatomy and use of intraoperative adjuncts such as image guidance and neuromonitoring. The surgeon's experience along with a definite learning curve remains key to successful surgical results and outcomes.,,,
Compartmental resection of insular gliomas by using meticulous microsurgical dissection along with the use of intraoperative adjuncts such as neuronavigation and neurophysiological monitoring makes this surgery safe and efficacious with minimum morbidity.
Declaration of patient consent
Full and detailed consent from the patient/guardian has been taken. The patient's identity has been adequately anonymized
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7]