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Table of Contents    
VIDEO SECTION-OPERATIVE NUANCES: STEP BY STEP
Year : 2021  |  Volume : 69  |  Issue : 6  |  Page : 1557-1559

Gravity Assisted Retraction Less Occipito Transtentorial and Trans-Splenial Approach for Posterior Third Ventricular Dermoid


Department of Neurosurgery, Sanjay Gandhi Post Graduate Institute of Medical Sciences, Lucknow, UP, India

Date of Submission04-Sep-2021
Date of Decision18-Oct-2021
Date of Acceptance25-Oct-2021
Date of Web Publication23-Dec-2021

Correspondence Address:
Dr. Jayesh Sardhara
Department of Neurosurgery, Sanjay Gandhi Post Graduate Institute of Medical Sciences, Lucknow, UP
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0028-3886.333527

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 » Abstract 


Background and Introduction: A dermoid is an inclusion cyst. Its presence in the posterior third ventricle is highly infrequent. It usually compresses rather than infiltrates the posterior third ventricle's anatomical structures due to a well-defined capsule. Hence, the surgical anatomy in these tumors is less distorted. The approach to the posterior third ventricular tumors depends upon their relation to the galenic venous complex.
Objective: This video abstract presents a case of the posterior third ventricular dermoid operated by gravity-assisted retraction less occipito transtentorial combined with the trans-splenial approach.
Surgical Technique: A 36-year-old gentleman presented with a headache without any neurological deficits; the magnetic resonance imaging (MRI) revealed a well-defined heterogeneous lesion in the posterior third ventricular region. It was mainly toward the right side, just beneath the splenium, pushing the galenic venous system downward. This made the occipital transtentorial approach favorable as it required the least vessel handling. A right parieto-occipital craniotomy was performed. The patient was placed in a lateral semi-prone position with the head slightly rotated toward the right side with a slight neck extension. This allowed the right occipital lobe to fall away from the Falco-tentorial junction. With sharp dissection, an inter-Rosenthal corridor was made. But as the tumor was higher up in the posterior third ventricle, it was modified to another trans-splenial corridor. Near-total excision was achieved with a thin capsule left attached to the vein of Galen. The capsule was thick, filled with a cheesy white material, and a calcified sebaceous lump within. The postoperative scan showed no residual tumor.
Results: The patient had improvement in the headache. There were no field cuts. The histopathology was suggestive of a dermoid cyst.
Conclusions: Dermoid cysts of the posterior third ventricular region are rare, and judicious surgical decisions result in better outcomes.


Keywords: Dermoid cyst, occipital transtentorial approach, trans-splenial approach
Key Message: Occipital transtentorial approach is a safe surgical technique to deal with the posterior third ventricle dermoid.


How to cite this article:
Sardhara J, Kumar A, Srivastava AK, Nangarwal B, Behari S. Gravity Assisted Retraction Less Occipito Transtentorial and Trans-Splenial Approach for Posterior Third Ventricular Dermoid. Neurol India 2021;69:1557-9

How to cite this URL:
Sardhara J, Kumar A, Srivastava AK, Nangarwal B, Behari S. Gravity Assisted Retraction Less Occipito Transtentorial and Trans-Splenial Approach for Posterior Third Ventricular Dermoid. Neurol India [serial online] 2021 [cited 2022 Jan 20];69:1557-9. Available from: https://www.neurologyindia.com/text.asp?2021/69/6/1557/333527


The dermoid cyst is a rare benign tumor of the posterior third ventricular region. Common surgical approaches for this region include the supra-cerebellar infratentorial, occipital transtentorial, and posterior interhemispheric.[1],[2] Other techniques include anterior transcallosal transventricular approach, lateral paramedian infratentorial approach, and stereotactic biopsy. The decision for the surgical approach depends on factors like the displacement of the galenic venous complex and asymmetrical extension to either side. We selected the right occipital transtentorial approach because the tumor had asymmetric extension toward the right side, and the galenic venous complex was shifted downward by the tumor.[3],[4] The video demonstrates the surgical technique of gravity-assisted retraction less occipito transtentorial and trans-splenial approach for the posterior third ventricular dermoid.


 » Objective Top


The video in this article demonstrates a right-sided gravity-assisted occipital transtentorial approach for a posterior third ventricle dermoid cyst.

Procedure

The patient was operated on under general anesthesia. With two wide bore cannula, the central venous pressure line, an arterial line, adequate intravenous access was taken. The patient was positioned in a lateral semi-prone position with the head slightly rotated toward the right side with a slight neck extension and fixed with a Sugita frame. With the help of gravity, the occipital lobe falls to avoid any brain retraction. The sagittal sinus, transverse sinus, and torcula were the important landmarks marked before the incision. Then a parieto-occipital craniotomy was done, exposing the posterior sagittal sinus, transverse sinus, and torcula. The dura mater was opened in a T-shaped manner, and the occipital horn was tapped with a ventricle catheter. Straight sinus was identified, and the tentorium was cut 1–2 cm lateral to the straight sinus. Then, through the galenic venous system, the tumor was approached, but the tumor was also extended inferior to the splenium, approached with the combined trans-splenial approach. Near-total excision of the tumor was achieved.

Video link: https://youtu.be/yffrHvNA2sk

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Video timeline with audio transcript

0.05–0.14 min: A 36-year-old gentleman presented with a headache and one episode of seizure without neurological deficit.

0.14–0.26 min: The radiological image was suggestive of a well-defined heterogeneous lesion in the posterior third ventricular region, mainly toward the right side, just beneath the splenium, pushing the galenic venous system downward.

0.26–0.36 min: The patient was placed in the lateral semi-prone position with the head slightly rotated toward the right side with a slight neck extension.

0.36–0.46 min: A right occipital scalp incision was made, and a right parieto-occipital craniotomy was performed, exposing the transverse sinus, superior sagittal sinus, and torcula.

0.46–1.53 min: The cerebrospinal fluid (CSF) was drained from the right occipital horn to relax the brain and facilitate the retractor's less wide exposure of the posterior incisura structures. At the level of the incisura, meticulous arachnoidal dissection and preservation of the veins were important objectives. The arachnoidal dissection along significant veins defined the venous corridor and ensured a bloodless trajectory, decompressing the posterior splenial region, and helping in draining the CSF from the quadrigeminal cistern. The venous plexus could be seen embedded with thick white arachnoid adhesions. Fine dissection was performed along the venous plexus to expose the intervenous corridor to the tumor. Sharp cutting off the thick arachnoid adhesions along the vein helped in the mobilization of the vein and facilitate the exposure of larger corridors to the posterior third ventricle.

1.53–2.30 min: Rosenthal veins coming from both sides via the ambient cistern met the vein of Galen in the quadrigeminal cistern. The idea was to dissect the inter-Rosenthal corridor to approach the posterior third ventricular region for tumor dissection. The trajectory of the straight sinus leads to the incisura. It was not far away from the torcula. A common mistake was to lose track and go along the surface of the tent lateral to the incisura, retracting the occipitoparietal lobe, and not being able to find the free edge of the tentorium.

2.30–3.32 min: The tent was cut anterograde or retrograde, taking care to coagulate adequately as some venous channel could be present within the tentorium. It was cut within 1–2 cm lateral and parallel to the straight sinus. The tentorium was composed of two layers. Both needed to be coagulated to avoid venous bleeding during the tentorial division. Any venous lake directly connected to the sinus should be avoided to be cut during this procedure. While dividing the tentorium close to the incisura, the position of the basal vein of Rosenthal and the vein of Galen must be ascertained, so that the injury to this vein may be avoided.[5] The edge of the tent should be hooked and retracted to expose the inter-Rosenthal and the splenial corridor.

3.32–4.05 min: As the tumor was situated high up in the posterior third ventricle just below the splenium and had pushed the veins down, we chose a corridor between the vein of Galen and the splenial vein.[3],[4] Dissection around the splenial vein was done to expose the lowermost part of the splenium, and thus, a trans-splenial corridor was used to approach the tumor.

4.05–5.09 min: The thick tumor wall was coagulated and opened. Cheesy off-white material was seen coming out through the opening. Calcified sebaceous material was seen within the tumor capsule suggestive of a dermoid cyst.[1],[2] The tumor capsule was dissected from all around, from the venous plexus, and the pulvinar of the thalamus, and the capsule was completely excised.

5.09- 5.35 min: After the decompression of the tumor, the occipital transtentorial approach provided adequate access to the habenular commissure and the pineal recess. These occult spaces should be looked for any residual tumor. The aqueduct is not directly visible because it is hidden by the posterior commissure's oblique orientation and the corpus callosum's overhanging splenium.

5.35- 5.41 min: The postoperative scan was suggestive of complete tumor excision.

5.41- 6.00 min: In the postoperative period, the patient had improvement in headache. There were no visual field cuts and the patient was discharged on the fifth postoperative day without any neurological deficits. The histopathology was suggestive of a dermoid cyst.

Outcome

After surgery, the patient had significant improvement in headache without any neurological deficit. The postoperative CT scan showed complete removal of the tumor. The patient was discharged on day 5.

Pearls and pitfalls

The position of the superior sagittal and transverse sinus should be marked before turning the head laterally. In the case of parieto-occipital lobe bulging, trigone should be tapped to release CSF, facilitating the interhemispheric corridor opening. An ultrasound-guided tap is preferred as the orientation is complex after positioning. A wide opening of the interhemispheric corridor is recommended, which can be done by elevating the head end of the table to gain an anterior interhemispheric trajectory, and lowering down the head end of the table helps achieve the posterior interhemispheric trajectory. The tentorium should be divided parallel to the straight sinus, and both layers should be coagulated first before dividing the tentorium to avoid venous bleeding. Inferior sagittal sinus and the free edge of the falx may be excised to get access to the contralateral side of the straight sinus. At the level of incisura, a meticulous arachnoidal dissection should be done to avoid venous injury. Usually, the space between the internal cerebral vein and the vein of Rosenthal is not enough to enter the posterior third ventricle. However, any growing tumor in this region shall push these veins superiorly and splay them widely.[4]

The disadvantage of this approach includes obtaining an adequate corridor between either the posterior parietal anastomotic veins or veins of the deep venous system. The approach for the contralateral extension of the tumor part is very difficult. However, one can even access a tumor of the contralateral ependymal lining due to oblique trajectory, but the ipsilateral attachment may be challenging to access.[4],[5]


 » Discussion Top


Endoscopic approach and cyst decompression are common approaches used by many neurosurgeons in the current era. However, adequate decompression may not be feasible via this approach in some instances. Various other approaches which were described earlier also should be in consideration for approach selection. This differs mainly due to the experience and comfort of the operating surgeon.[4],[5] We preferred the gravity-assisted retraction less occipital transtentorial approach in our case.


 » Conclusions Top


In this surgical video, we have demonstrated a gravity-assisted retractor less occipital transtentorial and trans-splenial approach to a posterior third ventricular dermoid cyst and successful complete excision of the tumor. Gravity helps in the fall of the occipital lobe, which helps avoid injury to the lobe during retraction. The operative nuances have already been described.

Declaration of patient consent

A complete and detailed consent from the patient/guardian has been taken. 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 medico-legal issues arising out of issues related to the patient's identity or any other matters arising from the public display of the video.

Financial support and sponsorship

Nil.

Conflicts of Interest

There are no conflicts of interest.



 
 » References Top

1.
Aoki H, Abiko S. Dermoid cyst of the third ventricle in a child (author's transl). No Shinkei Geka 1978;6:1049-53.  Back to cited text no. 1
    
2.
Caldarelli M, Massimi L, Kondageski C, Di Rocco C. Intracranial midline dermoid and epidermoid cysts in children. J Neurosurg 2004;100:473-80.  Back to cited text no. 2
    
3.
Behari S, Garg P, Jaiswal S, Nair A, Naval R, Jaiswal AK. Major surgical approaches to the posterior third ventricular region: A pictorial review. J Pediatr Neurosci 2010;5:97-101.  Back to cited text no. 3
[PUBMED]  [Full text]  
4.
Lozier AP, Bruce JN. Surgical approaches to posterior third ventricular tumors. Neurosurg Clin 2003;14:527-45.  Back to cited text no. 4
    
5.
Moshel YA, Parker EC, Kelly PJ. Occipital transtentorial approach to the precentral cerebellar fissure and posterior incisural space. Neurosurgery 2009;65:554-64.  Back to cited text no. 5
    




 

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