Endoscopic Supra-ethmoidal Approach for Anterior Cranial Base Resection: Tailoring the Approach for Maximum Exposure with Preservation of Nasal Structures. Anatomical Study and Surgical Cases

Background: The traditional endoscopic anterior cranial base resection involves total removal of the ethmoid including middle and superior turbinates to achieve good exposure of the slope of the anterior cranial base. In the past decade, teams of endoscopic cranial base surgeons have been successfully using this approach to treat a variety of intracranial pathologies: olfactory groove meningiomas, dermoids, schwannomas and other intracranial tumors attached to the anterior cranial base. In those procedures, the nose is utilized just as a route to the skull base since there is no disease in the nasal cavity to be addressed.

The complete removal of the ethmoid including the middle and superior turbinates is associated with increased volume of the nasal cavity postoperatively and permanent change of the nasal airflow. These factors predispose the patient to chronic nasal crusting and need for long-term follow up for nasal debridement. Techniques that envision preservation of the nasal structures maintaining great exposure of the anterior cranial base are desired, especially when treating patients with intracranial pathology only and no nasal disease.

Objective: To describe the step-by-step technique and feasibility of the supra-ethmoidal approach for anterior cranial base resection with maximal exposure of the anterior cranial base maintaining the middle turbinate, middle meatus and osteomeatal complex intact.

Methods: Three fresh cadaveric heads were used for dissections. The approach started with the harvesting of the nasoseptal flap. Then a Draf III frontal sinusotomy with preservation of the middle turbinate attachment bilaterally was performed. Superior septectomy was completed with exposure of the olfactory cleft. The middle turbinates were lateralized and the superior aspect of both ethmoids was removed with great exposure of the anterior cranial base. Bilateral sphenoidotomy was performed followed by resection of the anterior cranial base and exposure of dura. After the cadaveric dissection, this technique was performed in two patients with large olfactory groove meningioma. In both cases reconstruction was performed with nasoseptal flap.

Results: The dissection in anatomical specimens achieved in all cases satisfactory exposure of the cranial base preserving the middle turbinate, uncinate process, the ethmoid bulla and middle meatus intact bilaterally. Successful removal of large olfactory groove meningioma was performed in two patients utilizing this approach.

Conclusion: The endoscopic supra-ethmoidal approach for anterior cranial base resection is a feasible and safe approach that maximizes preservation of the nasal structures while having optimal access to the anterior skull base. It can be used in pathologies that involve the anterior cranial base and do not involve the nasal cavity.