Applied anatomy of extraocular muscular nerves

Objective To provide anatomic data for avoiding damage the extraocular muscular nerves during the intraorbital operation.Methods Microanatomic method was used to observe the location, course and syntopy of the oculomotor, trochlear and abducent nerves on 30 adult cadaveric heads (60 sides of orbits). Results (1)The trochlear nerve entered into the orbital side of one third of superior oblique muscle, it was neighboring frontal nerve when it crossed superior levator muscle; (2)There were arteries where the abducent nerves went into lateral rectus muscles (86.67%). If the belly of lateral rectus muscle was divided into three superior-inferior parts, nerve entered into middle one third commonly;(3)Superior division of oculomotor nerve coursed between optic nerve and superior rectus muscle after it left zinn ring, its branches entered into the superior rectus muscle and levator muscle. Inferior division of oculomotor nerve branched into medial rectus, superior rectus and superior oblique muscles. The branches which entered medial rectus muscle went under the optic nerve. There were 2~5 branches which entered inferior rectus muscle. Entering muscle point was on middle and posterior one third of muscle. Inferior oblique musclar branches were located at superior-lateral inferior rectus muscle. Conclusions The trochlear nerve should be protected through the space between superior oblique and the superior levator, rectus muscles into the optic and orbital apex. The oculomotor and abducent nerves should be protected during the operation of orbital apex.