Innervation of Orbicularis Oculi by Trochlear Nerve: Word of Caution.

Background: Neurosurgeons who operate in and around the pathway of the ocular nerves should have good knowledge of not only their normal anatomy but also their variations.
Case Description: During routine dissection of the orbits in an adult cadaver, an aberrant branch of the right trochlear nerve continued on to innervate the orbicularis oculi muscle. In this case, the trochlear nerve also provided a branch to the supratrochlear nerve.
Conclusions: Surgeons who operate along the pathway of the trochlear nerve such as the cavernous sinus should be aware of such an anatomic variant in order to avoid unwanted complications such as weakness of the orbicularis oculi muscle.
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