Surgical Management of Compressive Optic Neuropathy due to Orbital Osseous Lesions

Optic neuropathy due to compression of the optic nerve is a rare condition caused by a variety of pathologic conditions including tumor, infection, bone dysplasia or trauma. The diagnosis of optic nerve compression due to an osseous lesion is often determined by computed tomography (CT) scans, with thin slices in the axial and coronal planes, as well as visual acuity and visual field testing performed by an ophthalmologist. When conservative medical management with high dose steroids and immunomodulating agents fail to halt the progression of vision loss, surgical intervention is often required. Multiple surgical approaches have been described for orbital decompression including transorbital and transantral approaches, extranasal transethmoidal approaches and neurosurgical or craniotomy approaches. Transnasal endoscopic optic nerve decompression, however, has mostly been described in the setting of orbital trauma and few series exist describing its utility in the treatment of nontraumatic, compressive optic neuropathy. The course of the optic nerve is divided into three segments including the intraorbital, intracanalicular and intracranial segments. The intracanalicular portion is the most common site of osseous compression where endoscopic surgery allows access to the medial and inferior aspects of the nerve. The nerve is typically encountered just superior to where the internal carotid artery creates a bulge in the lateral wall of the sphenoid sinus. The ophthalmic artery usually enters the nerve sheath from an inferolateral direction, away from the medial endoscopic approach. Preoperative imaging, however, is important to identify the 10-15% of cases where the nerve travels through a posterior ethmoid or Onodi cell and the 15.5% of cases when the ophthalmic artery is susceptible to injury along the medial aspect of the optic canal. Discussion