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Page 8 of 15 Cossu et al. Mini-invasive Surg 2020;4:60 I http://dx.doi.org/10.20517/2574-1225.2020.52
[27]
microscopic endonasal approaches . This permits the performance of a precise bony decompression
around the sella, the medial cavernous sinus, the optic canal, and, if necessary, of the clivus and Meckel’s
[17]
cave . Furthermore, this approach allows the positioning of autograft fat between the tumor and
[28]
radiosensitive structures for further treatments .
After induction of general anesthesia, the endotracheal tube is positioned on the left of the patient and the
head should be slightly tilted to the left, turned to the right, and slightly flexed as for a standard endoscopic
endonasal transsphenoidal approach. The neuronavigation system is positioned to guide the procedure
and the volumetric MRI is fused with the bone-window CT to increase the precision of target definition.
Intraoperative monitoring is useful to monitor the function of the oculomotor and trigeminal nerves. The
face, the right periumbilical area, and/or the thigh are draped for graft harvesting if necessary.

In general, a binostril bimanual technique is preferred to obtain a wider range of movement. The primary
surgeon operates with dissecting instruments and the drill from the right nostril, while the assistant
surgeon manages the endoscope in the right nostril and the suction in the left nostril to keep the surgical
field clear. Alternatively, a contralateral uninostril approach can also be an option. The right middle
turbinate can be resected to widen access if needed during the procedure. Once the sphenoid ostium is
identified medial to the superior turbinate and superior to the choana, a wide sphenoidotomy is performed
with a posterior septostomy. A large exposition of the sphenoid sinus is necessary to identify the posterior
wall landmarks, including the tuberculum, sellar floor, and clival recess in the midline, as well as the optic
canals, carotid prominences, and optico-carotid recesses laterally.

A key part of the procedure is bony decompression of the sella, cavernous sinus, optic canal superiorly,
and upper clivus when necessary. The bone is generally removed with a high-speed diamond burr and the
ultimate eggshell layer is removed with a Kerrison rongeur to safely expose the dura. Constant irrigation
should be performed during the drilling to avoid thermic lesions to delicate neuro-vascular structures.
The medial and the anterior wall of the cavernous sinus are exposed after the ipsilateral side of the sella is
exposed. The medial optico-carotid recess is then progressively exposed. The optic canal unroofing is one of
[29]
the most important steps, which should be carefully performed as this could induce visual deterioration .
This part of the procedure is necessary when there is a reduction in the caliber of the optic canal and/or
when the patient presents with an optic neuropathy. Doppler ultrasound and neuronavigation are useful to
localize the ICA during the osseous decompression and before dural opening. Tumor removal should be
performed selectively with the goal of decompressing the optic nerve, the pituitary gland, and the cranial
nerves into the cavernous sinus. The medial portion of the tumor invading the sella should be initially
removed [Figure 7].

Subsequently, the dura over the cavernous sinus can be opened in a lateral to medial direction to avoid
injury of the ICA. Brisk venous bleeding is common after tumor removal and can be controlled with
hemostatic agents and temporary mechanical packing. A nerve stimulator is used to localize the course
of VI cranial nerve once the CS is entered. Visualization of cranial nerves is not necessary and often
dangerous. Electrocautery in the area should be avoided to prevent thermal injuries. Excision of the tumor
is done in a piecemeal fashion with curettes and ultrasonic aspiration (particularly useful with fibrous
tumors). The integrity of the lateral wall and the roof of the cavernous sinus should be respected. At the
end of the resection, a hypophysopexy is performed with the positioning of small pieces of fat between
the residual tumor and the pituitary gland to fill the dead space created by tumor removal and to better
delineate the target and provide a margin for adjuvant radiosurgery in order to protect radiosensitive
structures. In general, when a biopsy is performed for purely intracavernous lesions, there is no CSF
leakage. An artificial dural substitute or fascia lata from the thigh and glue are sufficient for skull base
reconstruction. A nasoseptal flap is rarely required. An endocrinological assessment should be performed
in the postoperative period and records are kept for fluid intake and urine output.