A Cadaveric Study of Trochlear Nerve Entry in the Tentorium and its Relations

The trochlear nerve is unique in its origin, course, and function, being the longest and thinnest among all cranial nerves, underscores the nerve's vulnerability during surgical procedures.

Thirty-two trochlear nerves from sixteen formalin preserved brains of human cadavers were examined. The course of the trochlear until it reaches the lateral wall of the cavernous sinus. Measurements made from the tentorial entry point to anterior clinoid process and posterior clinoid process, origin of the nerve until tentorium entry point, total tentorial length of the nerve noted.

We describe segment under the tent as "Subtentorial" segment, being separate from the tentorial segment. Mean distance between trochlear nerve and dural entrance on right and left sides was 28.08 mm and 27.95 mm, respectively. The mean length of tentorial segment was found to be 7.81 mm on the right side and 8.11 mm on the left side. The mean distance from the anterior clinoid process (ACP) to the dural entrance of the trochlear nerve on right side was 17.63 mm and the left side was 18.00 mm. The mean distance from the posterior clinoid process (PCP) to the dural entrance of the trochlear nerve was 12.97 mm on the right side and was 12.50 mm on the left side.

The study provides valuable prescience into the cadaveric anatomy of the trochlear nerve's entry into the tentorium emphasizing its application in various skull base surgeries.