Endoscopic Endonasal Approach to the Orbital Apex and Medial Orbital Wall: Anatomic Study and Clinical Applications

Objective: The objective of this study was to recognize the endoscopic anatomy of the orbital apex and medial orbital wall to understand the pure endoscopic endonasal approaches to this region and their clinical applications. These basic information will facilitate our surgical procedures and decrease the rate of surgical complications. Material and Methods: Five fresh adult cadavers were studied bilaterally (N = 10). We used Karl Storz 0- and 30-degree 4-mm, 18-cm, and 30-cm rod-lens rigid endoscopes in our dissections. After cadaver specimen preparation, we approached each orbital apex and medial orbital wall through each nostril. After resection of medial orbital wall, an endoscopic intraorbital approach was performed. Results: The orbita could be exposed by using 0- and 30-degree endoscopes. We preferred to start the approach from the sphenoid sinus instead of transethmoidal approaches that are less familiar to the neurosurgeons. The posterior and anterior ethmoidal arteries are in close relation to the supralateral wall of ethmoid sinus, thus care must be taken not to injure these arteries during dissection. In this way, we can safely expose the whole medial wall of the orbita. Optic canal decompression can be safely done by bone resection starting from the optic nerve toward the optic canal. We continued bone resection from the posterior to the anterior of the medial orbital wall, thus we can perform medial orbitotomy. The intraorbital approach can be done medially by introducing the endoscope between the medial and inferior rectus muscles. Conclusions: Our anatomic study offered the facility to learn the endoscopic anatomy of the orbital apex and the medial wall of the orbita and understand the appropriate approaches (such as medial orbitotomy and optic canal decompression) to some pathologic lesions of this region. With skilled and experienced hands, it can superimpose many traditional orbital approaches with minimal invasiveness and less postoperative complications.