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Avery et al. Mini-invasive Surg 2021;5:17 https://dx.doi.org/10.20517/2574-1225.2021.05 Page 5 of 18

evaluate the relevant paranasal sinus and skull base bony anatomy, sphenoid sinus pneumatization pattern,
areas of dehiscence and presence of hyperostosis. MRI should be thoroughly examined for tumor origin,
extension, and localization critical structures in relation to the tumor such as the optic nerves and chiasm,
ICAs and their branches, pituitary gland and infundibulum. Either CT or MR angiography may be indicated
for tumors that encase the vasculature for the purposes of surgical planning [Figures 2-4].

Surgical technique
At our center, the endoscopic endonasal transplanum/transtuberculum approach is performed as a binostril
technique with a neurosurgeon and otolaryngologist working together throughout the majority of the
procedure. The operation is begun with a 4 mm 0° rigid high-definition endoscope, with 30° and 45°
endoscopes available for use later in the procedure. Surgeon ergonomics are addressed by positioning a
high-definition monitor directly in front of each surgeon. A third monitor for neuronavigation is placed
between the 2 high-definition monitors [Figure 5]. Surgical steps are detailed in Video 1.

Patient positioning
The patient is positioned supine with the head tilted toward the left shoulder and turned 20° to 30° toward
the right. For an approach to the planum sphenoidale/tuberculum sellae, 10° to 15° of extension is used and
the head is fixed in the three-point Mayfield cranial fixation system. Optical neuronavigation is registered
and leads for somatosensory evoked potential monitoring are placed. The right lower quadrant of the
abdomen is prepped for a fat graft harvest.

Nasal preparation and approach
The nasal cavity is prepared prior to beginning the approach by spraying oxymetazoline in both nares. The
face, perinasal area, and right lower abdominal area (for fat graft harvesting) are then prepped and draped
in a sterile fashion. We have recently implemented a nasal rinse with a betadine solution diluted 1:1 with
normal saline to minimize the risk of COVID-19 transmission.

The initial approach into the sphenoid sinus is performed by the otolaryngologist with the 0° endoscope.
Lidocaine 1% with 1:100,000 epinephrine is first injected into the middle turbinates and posterior nasal
septum bilaterally. Both inferior turbinates are first in-fractured then out-fractured. Similarly, the middle
turbinates are out-fractured, exposing the sphenoid ostia. Next, monopolar electrocautery with a curved
microtip is used to make a unilateral mucoperiosteal incision beginning immediately inferior to the
sphenoid ostium and extending to a point approximately 2 cm anteriorly, along the inferior vomer and
posterior nasal septum, before turning superiorly towards the olfactory groove [Figure 6]. The rescue flap is
elevated inferiorly and the septal olfactory strip above is elevated superiorly, preserving the olfactory fibers.
A nasoseptal flap is harvested on the contralateral side, ensuring the preservation of the septal olfactory strip
by using a similar mucoperiosteal incision that is carried laterally into the inferior meatus to harvest a
sufficiently wide flap. The nasoseptal flap is placed in the nasopharynx and kinking of the vascular pedicle is
avoided.

Next, a posterior septectomy is performed to connect the right and left nasal cavities. An attempt is made to
remove the bone in one piece to preserve the bone for skull base reconstruction. A wide sphenoidotomy is
then performed that extends lateral to the sphenoid ostia and generally to the floor of the sphenoid sinus
inferiorly and to the roof of the sphenoid/ethmoid junction superiorly. Using a 30° endoscope, the ethmoid
air cells are opened bilaterally to expose the laminae papyraceae and each septal olfactory strip is lateralized
along their respective fovea ethmoidalis. All mucosa of the sphenoid sinus is removed to facilitate adherence
of the nasoseptal flap at the conclusion of the procedure.