The unique features of the trochlear nerve, including its dorsal exit from the brainstem and its contralateral innervation, are seen in the primitive brains of sharks.
To compensate for this, patients with trochlear nerve palsies tilt their heads to the opposite side, in order to fuse the two images into a single visual field.
It sometimes receives a filament from the trochlear nerve, but this is possibly derived from the branch that goes from the ophthalmic to the trochlear nerve.
More over, while the abducens and the trochlear nerve each innervate one specific muscle, the oculomotor nerve has many functions including eyelid retraction and pupil constriction.
Superior oblique myokymia is an uncommon neurological condition caused by vascular compression of the trochlear nerve resulting in repeated, brief, involuntary episodes of movement of the eye.
Damages to these structures produce the ipsilateral presentation of paralysis or palsy due to the lack of cranial nerve decussation (aside from the trochlear nerve) before innervating their target muscles.
The eye will be displaced downward, because the superior oblique (innervated by the fourth cranial or trochlear nerve), is unantagonized by the paralyzed superior rectus, inferior rectus and inferior oblique.
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.
