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Page 12 of 18 Avery et al. Mini-invasive Surg 2021;5:17 https://dx.doi.org/10.20517/2574-1225.2021.05

TRANSCRIBRIFORM APPROACH TO PLANUM & OLFACTORY GROOVE MENINGIOMAS
Patient selection & surgical considerations
The endoscopic endonasal transcribriform approach is an effective way to approach olfactory groove
meningiomas as it provides direct access to the anterior cranial fossa floor dura and the feeding arteries.
Other advantages over tradition transcranial trajectories include lack of brain retraction, increased
possibility of Simpson grade 1 resection and excellent visualization of surrounding critical structures.
However, loss of olfaction is virtually guaranteed in this approach due to disruption of the olfactory fibers
traversing the cribriform plate. Furthermore, the anatomical limitations are well defined, restricting the use
of this approach to a subset of patients with smaller olfactory meningiomas. The orbits limit access laterally,
although the lamina papyracea can be removed and gentle displacement of the periorbita provides access to
the midorbital sagittal plane. Tumor involvement superiorly along the posterior wall of the frontal sinus
becomes increasingly difficult to visualize and reach. Careful patient selection with thorough evaluation of
MRI and CT imaging is required when using this approach to maximize success.

At our center we utilize a supraorbital craniotomy for the great majority of olfactory groove meningiomas
as it allows olfaction to be preserved in most cases, with laterality determined by the side with more
olfactory nerve involvement to preserve the unaffected olfactory nerve. This approach requires minimal-to-
no brain retraction, and endoscopes with angled instruments are used in patients with a deep olfactory
groove to remove tumor not visualized with the microscope [Figure 7].

Surgical technique
Patient positioning, approach and bony exposure
The patient is positioned with the head in slight extension similar to the transplanum/transtuberculum
approach. The same nasal phase proceeds with harvesting a nasoseptal flap, sphenoidotomy and bilateral
ethmoidectomies. One of the middle turbinates is often removed to fully expose the fovea ethmoidalis on
either side. Bilateral mastoid antrostomies may be performed to aid in identification of each lamina
papyracea. With the use of a 30° endoscope, mucosa is removed from the superior aspect of the nasal
septum and the anterior skull base, and a superior septectomy is performed. With the cribriform plate
exposed, the lateral boundaries with the laminae papyraceae are identified, as well as the posterior boundary
with the planum sphenoidale. The anterior border with the posterior table of the frontal sinus is identified
through the completion of a Draf III procedure with removal of the frontal sinus floor and inferior portion
of the interfrontal septum. A prominent frontal beak may need to be removed.

After completely exposing the cribriform plate and each fovea ethmoidalis, the bone is thinned down with a
drill. The bony prominences overlying the anterior and posterior ethmoid arteries are identified, carefully
thinned and removed. The arteries are then coagulated and divided to avoid an orbital hematoma. A
craniectomy is then completed with the drill and Kerrison rongeurs, the boundaries of which are
determined by the access required for the meningioma and dural tail. Hyperostotic bone is removed. If
removal of the crista galli is required, it is carefully dissected from the falx cerebri.

Tumor removal and skull base reconstruction
Exposed dura of the anterior cranial fossa is thoroughly coagulated to disrupt blood flow to the
meningioma. Lateral incisions are made on each side, followed by an anterior incision with transection of
the falx. It is important to cut the falx in a posteroinferior direction to avoid injuring the superior sagittal
sinus. An emissary vein through the foramen cecum may be encountered. Finally, a posterior incision is
made. Similar to removal of tuberculum sella meningiomas, the tumor is then internally debulked and the
capsule gently dissected from the surrounding orbitofrontal cortex using standard microsurgical techniques.