Oculomotor, Trochlear, and Abducent Nerves: Schema Anatomy
1. Ciliary ganglion
2. Short ciliary nerves
3. Inferior division of oculomotor nerve
4. Pterygopalatine ganglion
5. Abducent nerve (CN VI)
6. Ophthalmic nerve (CN V1)
7. Oculomotor nerve (CN III)
8. Trochlear nerve (CN IV)
Comment: This schema shows the motor innervation to the extra-ocular muscles (from CN III, CN IV, and CN VI) and the autonomic fibers. Parasympathetic fibers arise in the brainstem and course with the oculomotor nerve to the ciliary ganglion.
Postganglionic parasympathetics innervate the ciliary muscle (which accommodates the lens) and the sphincter muscle of the pupil.
Sympathetic fibers that synapse in the superior cervical ganglion send postganglionic fibers to the dilator muscle of the pupil.
Sensory innervation to the orbit arises from the ophthalmic division of the trigeminal nerve.
Clinical: Unilateral damage to the oculomotor nerve (CN III) can paralyze the 4 extra-ocular muscles innervated by this nerve (superior, medial, and inferior rectus muscles and inferior oblique muscle) and the levator palpebrae superioris muscle of the upper eyelid, causing ophthalmoplegia and ptosis (drooping of the eyelid). Additionally, parasympathetic fibers in CN III will be affected, causing pupillary dilation (unopposed sympathetic innervation of the dilator of the pupil) and an inability to accommodate the lens for close-up vision on the affected (ipsilateral) side.