Endoscopic transsphenoidal optic nerve decompression: an anatomical study.

Purpose: The endoscopic transnasal, transsphenoidal approach is considered by many a valid option to reach the sellar region and, in selected cases, to decompress the optic nerve. However, few data are available in literature about the real effectiveness of the procedure and the extent of nerve decompression needed to obtain a clinical result. The aim of this anatomical study was to describe the most important landmarks of the endoscopic transsphenoidal approach to the optic nerve.

Methods: Six silicone-injected cadaver heads were dissected via the endoscopic transnasal approach, performing a bilateral optic nerve decompression. The lateral optocarotid recess (OCR) and optic canal were identified in each case. Moreover, the relationship between the ophthalmic artery at its origin and the optic nerve was examined.

Results: Twelve decompressions of the optic nerve were performed, obtaining the following measurements: intercarotid distance 12 mm ± 1.5, median length of OCR 5 mm ± 1 and average length of optic nerve decompression 15 mm ± 2. The ophthalmic artery was observed emerging from the internal carotid artery (ICA) medially in six cases, ventrally in four cases and laterally in two cases.

Conclusion: A wide optic nerve decompression may be obtained with transsphenoidal approach. However, the risk of ophthalmic artery injury seems to be more relevant than with supratentorial approaches, due to the intimate relationship between artery and nerve on its inferior surface. Knowledge of anatomical landmarks, such as lateral OCR and the position of the ophthalmic artery, is useful to prevent this injury.