The trochlear nerve is unique among the cranial nerves in several respects.
This is due to impairment in the superior oblique muscle innervated by the trochlear nerve.
More rarely, the oculomotor nerve and trochlear nerve (third and fourth nerve palsy, respectively) are affected; both play a role in eye movements.
By 1998, there had been only one reported case of compression of the trochlear nerve by vessels.
The trochlear nerve supplies the superior oblique muscle, and when this muscle is non-functional (as in trochlear palsy) the eye "excyclotorts"; i.e. twists/rotates outward.
The oculomotor nerve comes out between the peduncles, and the trochlear nerve is visible wrapping around the outside of the peduncles.
Other names for fourth nerve palsy include superior oblique palsy and trochlear nerve palsy.
On either side of this band the trochlear nerve emerges, and passes forward on the lateral aspect of the cerebral peduncle to reach the base of the brain.
