Application of Topographical Anatomy of the Trochlear Nerve in Transtentorial Approaches: An Anatomic Study.

Publication/Presentation Date

8-29-2024

Abstract

BACKGROUND AND OBJECTIVES: Transection of the free edge of tentorium (FET) might be necessary when approaching cavernous sinus lesions, clip placement in certain posterior communicating artery aneurysms, or during transpetrosal and retrosigmoid transtentorial approaches. No anatomic study has investigated the relationship of the trochlear and oculomotor nerve and FET in an attempt to identify a safe zone for such maneuver.

METHODS: Ten embalmed specimens (20 sides) were studied and the following morphometric measurements were taken using digital microcalipers: trochlear (TP) to oculomotor porus (OP), length of the intratentorial segment of cranial nerve (CN) IV, nerve free FET, and distance along the oculomotor (CN III) from its OP to CN III/trochlear (CN IV) crossing and angle between the long-axis petrous ridge and TP (petrotrochlear angle).

RESULTS: The CN IV pierced the deep layer of the FET in all cases at a mean distance 8.11 mm (4.43-11.33) posterior to the OP, measured along the FET. CN IV continued within the tentorial edge for a mean of 6.17 mm (3.18-11.33) before entering the cavernous sinus at a mean distance of 1.9 mm (0-5.46 mm) from the posterior-most aspect of the OP. A nerve-free portion of FET was 1.93 mm (mean) (0-5.46). No nerve-free FET segment (<1 >mm) was observed in 4 sides (20%), and a nerve-free FET segment175° in 4 specimens (20%).

CONCLUSION: Our data confirm presence of the intratentorial segment of CN IV. Transection of the FET carries the lowest risk of CN IV injury if performed < 2 mm or >10 mm posterior to the OP, or posterior to intersection of the FET and a virtual extension of a petrous ridge.

ISSN

2332-4260

Disciplines

Medicine and Health Sciences

PubMedID

39207147

Department(s)

Fellows and Residents, Department of Surgery

Document Type

Article

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