January 06, 2016
This we do is a great example of how errors in choosing the appropriate operative corridor can lead to additional unnecessary procedures. This patient suffered from visual dysfunction, and I initially approached a mass through an endoscopic transnasal surgery. A subtotal resection was accomplished, and the residual tumor continued to grow, and therefore the patient required a transcranial approach via extradural clinoidectomy, to remove the additional growing residual tumor. So let's see what could have been done different in this case. This is the initial MRI, when the patient presented with visual dysfunction. You can see the mass is a typical tuberculum sellae meningioma, centered over the tuberculum sellae. It somewhat in cases, the vasculature. However, most importantly, the tumor invades both optic canals. Again, this invasion is not a contraindication and actually is a nice fit for the transnasal approach, as the transnasal route can easily decompress the nerve early on during the procedure. However, the mass extends beyond the boundaries of the optic nerve. As you can see, here is the vertical line passing through the optic nerve, and tumor slightly extends beyond these boundaries. I believe this feature of the tumor, in other words, again, its extension beyond the boundaries of the optic nerves is a contraindication to using the transnasal route, as the reach over the optic nerve is quite limited, and any blind dissection over the nerve is actually unsafe. Therefore, this lesion should have initially been approached via the transcranial operative trajectory. You can also see the hyperostotic feature of the tumor. This tumor also proved to be quite fibrous during the initial index operation. You can see that in the transnasal approach I was able to remove the tumor primarily on the right side, but the portion of the tumor over the optic nerve on the left side could not be adequately resected, since the tumor was quite fibrous and at hearing in this area and blind dissection of the mass from the thalamus in the floor of the third ventricles deemed unsafe. Unfortunately, this residual tumor continued to grow and the patient presented months later, after the initial transnasal operation, with left sided visual dysfunction and required a transcranial operation. Here, you can see the residual tumor that continued to grow. Here, you can see the previous reconstruction at the area of the tuberculum and sellae, from the transnasal operation. The residual mass continues to grow, and you can also see the amount of hyperostosis associated with the left clinoid process. The clinoidectomy most likely, will be quite complicated in this case, because of this significant amount of the bone that is hyperostotic, very firm, and is encasing the optic nerve, therefore, drilling has to be carefully performed in layers to protect the optic nerve and avoid its inadvertent injury. Here's the left pterional craniotomy. The lesser wing has been dissected. A lot more drain was used during this procedure to provide dural sac decompression early. The clinoid process is being hollowed out. Before further, clinoidectomy is completed extradurally. The roof of the optic nerve is drilled away to untethered the nerve. You can see the amount of hyperostosis over the optic canal. Implemented irrigation was used during drilling to prevent thermal injury to the nerve, that is very much embedded within the thick bone. Here's the thickness of the bone over the optic nerve, quite unusual. Here's the cortical bone over the optic nerve. After the bone is quite thin over the nerve, I used angle curettes. I avoid drilling directly over the dura, encasing the nerve as much as possible. Here's the nerve being decompress more medially, over the funnel bone. Here's the amount of decompression performed. Now the attachment of the clinoid to the funnel bone is being disconnected. Next, the clinoid process is being hollowed out. So it is also disconnected from the optic strut. The hollowed out process is now being dissected from the clinoidal ligaments, and is being extracted. This early decompression of the nerve is quite effective, so that the falciform ligament can be dissected intradurally to release the nerve. Here, you can see the final product of the clinoidectomy. Next, the dura is open in a curve and air standard fashion, the anterior aspect of the Sylvian fissure is opened. Here is the previous operative resection cavity. Here's the left side of the optic nerve. The falciform ligament over the nerve is transected, so that nerve is decompress early. You can see the side of strangulation of the nerve. Here's the tumor along the medial aspect of the optic nerve infiltrating the foramen that is being dissected from the nerve. Again, you can see the ring of discoloration around the nerve, where it was being pinched by the tumor, as the nerve entered the falciform ligament. The tumor was removed both lateral and medial to the nerve. Here's the ophthalmic artery, just inferior to the nerve. Additional tumor along the posterior aspect of the foramen is also dissected to prevent any risk of tumor regrowth and further invasion on the foramen. It is the portion of the tumor nearing the area of the chiasm. This capsule was quite adherent to the nerve more medially. However, sharp dissection was used to remove as much of the tumor as possible. All the perforating vessels were, however, perfectly protected. This very anterior portion of the tumor was sharply dissected from the nerve. Aggressive coagulation was avoided. Here, you can see the nerve quite free. Postoperative MRI demonstrates gross total resection of the mass without any complicating features. This patient's vision continued to improve after surgery. The important learning points about this case is, a proper selection of patients for the transnasal trajectory, specially in the case of fibrous tubercullum sellae meningiomas. In other words, the transnasal approach is obviously not a good fit for every tubercullum sellae meningioma. An extension of the tumor beyond the boundaries of the optic nerves is an important contraindication for the use of the transnasal approach. Thank you.
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