A young woman presented during the first trimester with profound visual loss and a suprasellar mass. We were concerned about a prolonged anesthetic in this patient during the first trimester and opted for an endonasal approach in order to minimize surgical time. The total procedure was under 2.5 hours with a complete resection. The image on the right in figure 2 represents the image guide scan using the Stryker-Leibinger system. Note the excellent accuracy that allows us to identify the planum just above the level of the pituitary and staying between the carotid arteries.

Figure 2: Image-guided localization

Once the initial sphenoidotomy is complete and the posterior ethmoidectomy is performed access to the planum is achieved. Using the image guided system the key bony landmarks are identified, specifically the optico-carotid recess and the medial clinoids. The planum sphenoidale is identified and an opening made exposing the space directly under the tumor and between the optic nerves and carotid arteries. (This is seen in figure 3.)

Figure 3: Initial transplanum exposure between optic nerves.

Once the bony exposure is completed the dura is coagulated and then opened. The tumor dissection is initiated and debulked (figure 4) Once the tumor is debulked and dissected away the subchiasmatic perforators can be visualized and preserved (figure 5 and 6) The tumor is dissected away from the membrane of Liliquist and freed from its adherence to the basilar artery. Figure 6 shows the basilar artery (BA) bifurcation and the posterior cerebral (PCA) and superior cerebral (SCA) arteries bilaterally with the third nerve in between, as seen from the nose via an endoscopic transplanum approach.

Figure 4: (4a) Initial internal debulking of the tumor; (4b) Following debulking the tumor dissected away from the chiasm.

Figure 5: Subchiasmatic perforators (P); Figure 6: Basilar artery (BA) dissection showing posterier cerebra (PCA)l and superior cerebral arteries (SCA).

Following removal of the tumor the decompressed chiasm can be visualized with perforators preserved (figure 7 and 8). Postoperative MRI confirm complete removal (figure 8). Note the decompression of the optic chiasm and the fat packing within the sphenoid sinus.

Figure 7 (Left): Post-removal view of the chiasm; Figure 8 (Right): Postoperative MRI with fat graph (FG).

This approach can be used to address lateral extension into the cavernous sinus when indicated. The figures below demonstrate a right transcavernous sinus approach in a patient with an invasive pituitary macroadenoma. The patient developed blindness in the right eye following previous transcranial surgery at another institution. The tumor continued to grow leading to impending visual loss in the remaining eye. Complete decompression of the left optic nerve was undertaken with recovery. Aggressive cytoreductive surgery was pursued with removal of the tumor in the right cavernous sinus in order to reduce the tumor burden for adjuvant therapy.

Dissection along the lateral compartment of the cavernous sinus reveals the third nerve and the meningohypophyseal artery (figure 9).

Figure 9: (a) Right lateral cavernous dissection; (b) The probe is on the third nerve lateral to the carotid artery.

The transplanum approach can be utilized for very large tumors. A 40-year-old male presented with anosmia and a large olfactory groove meningioma.

The patient underwent resection using an expanded endonasal approach with image guidance. Complete removal was achieved including dissection of the component adherent to the anterior cerebral artery. This was accomplished without the need for a craniotomy and the skull base was repaired through the nose without complication.

Figure 10 shows pre- and post-op images depicting a complete resection of the tumor. Notice the anterior cerebral arteries have been left intact. Since this approach avoids a craniotomy and brain retraction there is no disturbance of the brain parenchyma.

Figure 10: (a) Pre-op coronal view; (b) Post-op saggital view; (c) Post-op coronal view.

This preliminary experience has shown the feasibility of removing large and complex ventral lesions from the subchiasmatic space using an expanded endonasal approach with image guidance. The approach is minimally invasive and does not require a craniotomy. The transplanum dissection provides for complete control of critical neurovascular structures. Hemostasis does not seem to be prohibitive as even transcavernous dissections are feasible. This approach we believe is not only minimally invasive but is a more anatomic approach to preserve the critical vascularity of the chiasm and avoids brain retraction and manipulation.