Foramen Magnum Meningioma: Transcondylar Approach
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Let's discuss resection of ventral Foramen Magnum Meningiomas via the conservative or minimal Transcondylar Approach. This is a 60 year old female who presented with right-sided shoulder weakness and myelopathy. MRI evaluation revealed a sizable ventrally located foramen magnum meningioma, with evidence of significant brainstem and upper cervical cord compression. The tale of the meningioma along the clival dura is apparent. You can see the relationship of the vertebral arteries in connection with the mass. Let's review patient positioning. The patient is placed in the lateral position. So much sensory and motor evoked potentials are monitored. The head is turned about 45 degrees toward the floor, and a curvilinear incision is utilized. Again, you can see the location of entering at the point where a dot is marked. A scalp flap is reflected along with a suboccipital muscles. You can see the extent of the bony removal and minimal suboccipital craniectomy to the craniocervical junction. Vertebral artery is exposed, but it's not mobilized out of its groove. A very minimal condylectomy is completed until the lateral curvature of the foramen magnum is palpable. Further bony removal, essentially will not help further, since the vertebral artery is tethering the dura unless the vertebral artery is mobilized outside its groove. I do not believe vertebral artery mobilization is necessary even for very ventral foramen magnum meningiomas as demonstrated here. The lateral mass of C1, however, is drilled. You can see the venous plexus along the vertebral artery. Obviously a C1 laminectomy is also completed. The dura is incised along the edges of the bone work and the dura is tacked up aggressively, to maximize the lateral to anterior trajectory on the right side. The arachnoid bands are also incised. You can see the dura, despite the ventral location of the tumor. This exposure readily allows identification of the mass without significant retraction. Tumor was debulked. You can see the 11th cranial nerve, important cerebrovascular structures are identified early, including the vertebral artery, PICA, as well as the lower cranial nerves underneath the cerebellum. Next, the tumor is aggressively debulked, and the tumor appears to be quite fibrous. It is gently mobilized away from the vertebral artery. These tumors frequently involve the intradural origin of the artery. Here are the lower cranial nerves that are being mobilized from the superior capsule of the mass. Further dissection follows. Again you can see that the 11th cranial nerve is mobilized laterally. I call this the scouring technique. A pair of forceps are used to mobilize the tumor and roll the tumor laterally. Next a suction device is placed into the hole, where the forceps were initially placed in. Then, the suction device is kept within the center of the tumor to clear the operative field, while an ultrasonic S-spreader device removes the tumor. As this portion of the tumor is evacuated, similar steps are followed. In other words, the forceps create a hole in the capsule of the tumor and roll the tumor laterally. The suction device is placed into the initial hole of the forceps, clearing the operative field, while additional segments of the tumor are removed. Here's further mobilization of the tumor without significant manipulation of the spinal cord. Here's a very similar maneuver. If the capsule is very adherent to the pia of the brainstem and spinal cord, small sheet of the tumor should be left behind to avoid any significant neurological decline post-operatively. Here you can see the last pieces of the tumor that are brought into the resection cavity. One has to prevent quick return of this fragment of the tumor into the canal which could potentially hit the spinal cord. I continue to remove the tumor. Obviously the aspect of the dura that is infiltrated by the mass can not be resected. Therefore, the tumor is as aggressively curated away from the dura of the ventral spinal canal, and the portion of the dura is heavily coagulated. Here's the rest of the anatomy, vertebrobasilar junction right vertebral artery, PICA, lower cranial nerves, basillar artery, cranialcervical junction. No residual tumor is apparent. You can see the ventral dura was curated away and heavily coagulated. Here's the funnel resolved. Spinal cord and brain stem are nicely decompressed. Here's the postoperative MRI, which revealed gross total removal of the mass with aggressive decompression of the brain stem and spinal cord. And this patient made an excellent recovery and her preoperative neurological deficits resolved. Thank you.
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