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Supracerebellar Infratentorial Endoscopy for Quadrigeminal Cistern Epidermoid
Correspondence Address: Source of Support: None, Conflict of Interest: None DOI: 10.4103/0028-3886.304077
Keywords: Endoscopy, epidermoid, quadrigeminal, supracerebellar infratentorial
The traditional microscopic supracerebellar infratentorial approach has been a standard to access pineal region masses.[1],[2] However, this has a limited angle of illumination and visualization along the sides and corners, resulting in a tunnel vision. Hence, the required craniotomy is often more extensive, with some degree of cerebellar retraction. In comparison to the microscope, a standard endoscope offers a panoramic view with an additional option of using angled endoscopes[Figure 1].[3],[4]
Moreover, by rotating the angled endoscopes, an even greater field of view is possible. When an endoscope is used with coaxial surgical instruments, cerebellar retraction can be averted, as a narrow corridor is sufficient. Herein, we illustrate the technique of endoscopic supracerebellar infratentorial excision in a patient having quadrigeminal cistern epidermoid.
A 21-year-old male presented with progressive headache. On examination, there was papilledema. Magnetic resonance imaging (MRI) showed obstructive hydrocephalus due to an extra-axial mass in the quadrigeminal cistern, hypointense in T1WI, and hyperintense in T2WI, with no enhancement. Diffusion-weighted (DW) and apparent diffusion coefficient (ADC) imaging demonstrated restricted diffusion in the mass suggestive of epidermoid.
Supracerebellar infratentorial approach was chosen as the epidermoid was predominantly midline and inferior to the central veins. Endoscopy was chosen as a standalone tool for panoramic and angled illumination-visualization, avoiding cerebellar retraction. Video Link: https://youtu.be/UPym1HhIMdE. QR code:
Video timeline with audio transcript: 28.14 s: Sitting position is preferred, as irrigation fluid and blood tend to drain away from the endoscope. Head-holder fixation in maximal neck flexion and use of head-end of OT table for elbow support are key ergonomic tips. 41.48 s: 6 cm longitudinal incision and a 5 cm suboccipital craniotomy were made. Dura was cut in V shape and kept reflected. 50.44 s: The bridging veins were coagulated and cut, taking the 0° endoscope inside. 56.38 s: Using no retraction, the supracerebellar corridor is gently sailed through, without avulsing any vein. 1 min 4.03 s: A sharp incision is given over the thickened arachnoid over the inferior paramedian area. 1 min 13.11 s: The precentral cerebellar vein is exposed at the lower section, coagulated and cut. 1 min 25.37 s: The cavity of the epidermoid is entered, gentle bimanual intracapsular removal of the epidermoid flakes is performed using pituitary curettes with intermittent saline irrigation. 1 min 41.08 s: The endoscope can be fixed onto a holder with periodic adjustments, to enable bimanual dissection. 1 min 51.03 s: The superficial portion of epidermoid is most conveniently removed using 0° endoscope. 1 min 59.04 s: Profuse saline irrigation and soft suctioning are essential. 2 min 05.13 s: The internal cerebral veins and pineal body are appreciable now[Figure 2].
1 min 11.12 s: 30° endoscope is introduced now pointing inferiorly to remove the flakes from the cerebello-mesencephalic fissure exposing the corpora quadrigemina[Figure 3] and [Figure 4].
2 min 25.29 s: The angled endoscope can be rotated to view the lateral epidermoid extensions, and removeWd using angled instruments. 2 min 35.05 s: By turning the endoscope superiorly, we can appreciate the junction of Internal Cerebral Vein (ICV) with the vein of Galen. 2 min 41.43 s: Once the removal is complete, layered closure is done for good cosmesis. 2 min 47.28 s: Post-op MRI shows total resection with the resumption of aqueductal flow and resolution of hydrocephalus. Outcome The patient remained asymptomatic without the need for any intervention for at least 4 years.
The standard microscopic supracerebellar infratentorial approach is often limited by tunnel vision, necessitating more extensive craniotomy and some cerebellar retraction.[1],[2] This is significantly more relevant in pathologies such as epidermoid, which tend to have extensions along with the subarachnoid spaces.[3],[4] Endoscopy is progressively replacing microsurgery in various disease conditions due to the panoramic illumination-visualization and increasing resolution of endoscope cameras.[4],[5] As a result, the size of exposure needed can decrease to become more minimally invasive. Similar pathologies in quadrigeminal cistern are usually tackled both in sitting or prone positions. Prone position, though technically more straightforward, has many disadvantages, especially with the endoscope. The pooling of fluid and fogging of scopes can impede the visualization with a prone position, mandating continuous fluid irrigation.[6] In a sitting position, the endoscope is positioned superiorly and away from dissecting instruments so that the procedure becomes convenient. We prefer to fix the head using the Sugita head holder in maximal neck flexion, as shown in the video. The head end of the table serves as elbow support. The endoscope can either be fixed or held by an assistant for bimanual dissection of flakes. Coaxial or single shaft instruments do not crowd the operative field and are more suitable for handling along the side of the scope. The critical advantage of the endoscopic supracerebellar approach is in the utility of angled scopes. Angled optics have been shown not just to enhance the field of view but also to increase resection in some lesions.[7] By rotating the angled scope, we can visualize every nook and corner of the operative area, which are otherwise inaccessible, so that cerebellar retraction can be avoided totally. One of the limitations of this approach may be vascular lesions, wherein blood spillage is likely to interfere with the endoscopic view, making it difficult to achieve hemostasis.
The endoscopic supracerebellar infratentorial approach provides a panoramic and angled view of the quadrigeminal region. Most pathologies except vascular lesions can be tackled through the narrow corridor, without any cerebellar retraction. Declaration of patient consent The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.
[Figure 1], [Figure 2], [Figure 3], [Figure 4]
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