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Cadaveric Dissection: Midline Supracerebellar Approach and Transtentorial Modification

July 22, 2016

Transcript

This video reviews the anatomical landmarks and findings during the midline supracerebellar approach toward the pineal region, also reviews any less of technique for the transtentorial modifications of this approach. You can see the midline incision, the area of engine. Two burr holes are created just over or just below the transverse sinus. Only removal has to be carried out carefully to avoid any injury to the dural venous sinuses. Only the tip of the drill comes in contact with a wall of the sinus or the dura. The side cutting bur is not touching the surface of the soft tissues or the dura. Here, you can see the lining of the roof of the sinus. Here you can see the edge of the transfer sinus on the left side. Here's the extent of our craniotomy. Foramen magnum is not opened. This is primarily a midline supracerebellar approach. Drilling continues from each burr hole to where they kill. Next, the most critical part of the bone work is performed over the dural venous sinuses, including the torcula. A B1 bit without a footplate is used to thinned it more over the dural venous sinuses. The footplate is avoided at this location. Next to bone flap is gently mobilized by fracturing the residual thin cortical bone in our cortical bone over the dural venous sinuses. You can see the bone is mobilized inferiorly to avoid inadvertent injury of the dural venous sinuses, during mobilization of the bone flap. Next, additional bone over the torcula and the transfer sinuses is removed so that the duro camera reflected superiorly while providing ample amount of space through this supracerebellar corridor. First the bone is thinned down and [indistinct] are used to remove the thin shell of bone over the dural venous sinuses. Here, you can see the extent of bone removal, dura's tented up superiorly. Traction sutures are placed into the tentorium, just interior transverse sinuses to further mobilize the Duramorph superiorly expanding the operative corridor through this supracerebellar corridor. Here, you can see the expanded pathway toward the pineal region. Some of the midline bridging veins have to be sacrificed. Let's go ahead and continue our deception over the cerebellum to reach the pineal region. Some of the thick raknoid bands or this area are dissected. Here's an internal occipital vein, vein of Galen. Morty magnified view toward the pineal region is also provided. Here's further dissection of the veins in vein of Galen. Vein of Rosenthal fell on the left, enough Rosenthal on the right and the precentral cerebellar vein that can be safely sacrificed. Here's the internal occipital vein coming from the occipital lobe. Here's the pineal gland. You can see the viewing angle is changed more inferiorly so that pineal region can be exposed. Here are sum of the tributaries to the vein of Rosenthal. The precentral vein is sacrificed, area of pioneer region is now more in view. Going over the pineal gland, one can enter the posterior third ventricular. Some of the smaller legions in this area can be removed through this pathway. Some of the P3 and P4 branches from the posterior cerebral artery are also apparent. Here's an internal cerebral vein, pair of them demonstrated here. Here you can see both internal cerebral veins along the roof of the third ventricle. Here's further anatomy of the venous structures in this area. Again, the internal occipital vein on the right side, vein of Rosenthal, vein of Rosenthal, pair of internal cerebral veins, just anterior to the precentral cerebellar vein. Looking into the posterior third ventricular, again the location of internal cerebral veins. Here's the transtentorial modification of this approach. A section of the tentorium can be safely removed, just anterior to the transfer sinus, until the basal occipital lobe is exposed. Depending on the location or the pathology, sizable length of the tentorium can be incised, and a portion of it can be resected. There are venous legs often present. These legs can be sealed using thrombin-soaked Gelfoam. Obviously the fourth ventricle is located at the edge of the tentorium and has to be protected during the more anterior part of the tentorial sectioning. The posterior basal temporal lobe can also be exposed through this approach. And more lateral incision within a tentorium is also completed. So this section of the tentorium can be removed Again, the trochlear nerve has to be identified at the edge of the tentorium before the most anterior incision is executed. Here, you can see some of the branches of the posterior cerebral artery. Pathology within this area is readily accessible. In the more distal part of the PCA, the internal occipital vein. Further extension of the stress cortical incision can reach the more posterior part of the temple horn. Further dissection of the cerebrovascular structures in the area is demonstrated. This form of approach to the posterior basal temporal lobe avoids significant retractions often required for reaching this area using supratentorial corridors. Thank you.

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