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Brainstem Pilocytic Astrocytoma: Supracerebellar Approach

January 21, 2016


Let's review another example of the use of paramedian supracerebellar approach for a section of large pineal region tumors and this case, a pilocytic astrocytoma. This is a 46 year old female who presented with progressive headaches was known to have a history of tectal glioma as a child that was treated via VP shunting. A recent MRI evaluation revealed a cystic mass in the area of the pineal region. There is evidence of a normal tectum over the tumor. This tumor is primarily located on the right side. Due to the inferior extension of the tumor, a paramedian approach from the right side would be quite effective as the inferior slope of the tentorial surface of the cerebellum provides a more inferior trajectory toward the poles of the tumor. The patient was placed in a lateral position. Paramedian linear incision was used. You can see the location of the transverse sinus. A lumbar drain was installed for dual decompression of the brain. You can see the small craniotomy the midline is located here. The transverse sinus is unroofed. The cerebellum is dissected and two sutures are placed just anterior to the transverse sinus in the tentorium to mobilize the transverse sinus superiorly. The supracerebellar corridor was exploited interacting with bands or the posterolateral mesencephalon were dissected. The supratrochlear window was used to remove this tumor. Here are some of the branches of the supracerebellar artery. Can see a distal segment of the trochlear nerve. Portion on the occipital lobe had herniated toward the posterior fossa, small opening within the dorsal lateral mesencephalon was completely ended. Ultrasonic aspirator was used to remove this pilocytic astrocytoma. You can see this opening was extended more inferiorly while preserving the trochlear nerve. This portion of the mesencephalon was affected by the tumor. As much of the tumor as possible was removed until the relatively normal appearing peritumoral area was exposed. Here is our location via neuronavigation. Tumor removal is continued on both sides, until the posterior aspect of the third ventricle is encountered. Here's part of the tumor affecting the ipsilateral tectum. Here the tumor is being debulked. Now we continue to move toward the right side and in midline to remove additional part of the tumor that is around the in suture. Here's the posterior aspect of the third ventricle that is encountered at the end of our resection. Aggressive coagulation is avoided. Gentle tamponade is used. You can see that contralateral parts and our reach way toward the left from the right side, using the crosscore trajectory. Here's the walls of the third ventricle, relatively clean. Walls of the resection cavity on smaller the anterior extent of our tumor removal, a demagnified view of our operative corridor with minimal injury to the cerebellum. And postoperative MRI revealed adequate resection of the tumor without any complicating feature. Thank you.

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