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Medial Tentorial Meningioma: Supracerebellar Transtentorial Approach

November 11, 2015

Transcript

The supracerebellar transtentorial approach is quite a useful route for a section of medial tentorial meningiomas and other intra-axial tumors within the posterior basal temporal lobe without significant retraction of the temporal lobe, specially on the dominant side. This is a 34 year old female who presented with headaches and mild dysphasia, and my evaluation revealed a left sided medial tentorial meningioma with moderate amount of edema. Further imaging reveals the location of this meningioma. The traditional approaches to this tumor involve as subtemporal approach. However, this tumor is located very medially along the slope of the tentorium and significant amount of temporal lobe retraction would be necessary, which can lead to venous infarction, retraction edema and potentially significant injury to the vein of Labbe. I elected to use a paramedian supracerebellar transtentorial approach. In other words, coming this way, as you can see at the tip of the arrow, cutting the tentorium affected by the tumor and creating a window to make the tumor drop down into the posterior fossa. This route provides an excellent opportunity for a Simpson one grade resection because the part of the tentorium that is affected by the tumor will also be removed, but more importantly, significant retraction of the dominant temporal lobe will be avoided. Angiogram demonstrated a relatively hypervascular tumor. Most of the vascularity is peal in nature. Before we proceed with the intraoperative events, let's go ahead, review the positioning and the relevant anatomy. You can see the patient was placed in the latter position, head turned toward the floor and a hockey stick incision was used to complete a generous paramedian craniotomy. Let's go ahead and review the anatomy via cadaveric dissection before we jump in the intra-operative findings and review them. Here's the craniotomy for this procedure, the burr holes over the transverse sinus and the reflection of the muscle flap. Let's go ahead and review the cadaveric dissection, again on the left side. A window is created through the tentorium. You can see the cerebellum, a supracerebellar corridor. Adequate size window is removed. Obviously the straight sinus is protected during the medial incision. Next, the anterior part of the window is created. Here's the exposure, directly toward the posterior basal temporal lobe, as well as the occipital lobe. The PCA branches are relatively accessible. In any extra-axial or intra-axial tumor, including arteriovenous malformations, may be removed. Here is the pineal region. Posterolateral aspect of the mesencephalon is also easily reachable. Here's the entry into the third ventricle. Colliculi and the pineal region are also exposed. Let's go ahead now, review the intra-operative events. Left sided supracerebellar craniotomy accomplished. The transverse sinus was on roofed, two sutures were placed along the posterior aspect of the tentorium, so that the transverse sinus can be gently elevated and mobilized. This is really an important maneuver to expand the operative corridor. Next, a window is created around the base of the tumor. Can see the use of these sutures, so minimal retraction of the cerebellum is necessary. Here's the window around the base of the tumor. Obviously ample amount of coagulation is necessary to devascularize the tumor. This maneuver allows early devascularization of the tumor. Small pieces of cotton are used to mobilize the brain away from our maneuvers during resection of the tentorial window. Here's the tumor, located upstairs. I continue to find the neurovascular structures early on along the anterior edge of the tumor. This is another advantage of this approach. Next, the tumor is debulked and gently dissected into our resection cavity. Here, you can see the large piece of the capsule that is being extracted. Here's the piece of the tumor that was removed and the postoperative MRI demonstrated complete removal of the mass. The affected part of the tentorium was also resected and this patient made an excellent recovery, thank you.

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