Chapter contents Overview Origin, central course Intracranial course Final innervation Clinical correlation Unique features

Cranial Nerve IV - Trochlear Nerve Page 6 of 7 Clinical Correlation The superior oblique muscle normally depresses, intorts, and abducts the eye (fig. 4-6a). Damage to the trochlear nerve will present as: Extorsion (outward rotation) of the affected eye due to the unopposed action of the inferior oblique muscle. Vertical diplopia (double vision) due to the extorted eye. Weakness of downward gaze most noticeable on medially-directed eye. This is often reported as difficulty in descending stairs. Figure 4-6a. Normal action of the superior oblique muscle.

Figure 4-6b. Paralysis of the superior oblique muscle.

		Extortion (outward rotation) of the affected eye due to the unopposed action of the inferior oblique muscle (Fig. 4-6b). Vertical diplopia (double vision) due to the extorted eye. Weakness of downward gaze most noticeable on medially directed eye. This is often reported as difficulty in descending stairs. Head tilt (Fig. 4-6b): patient will often tilt his head opposite the side of the affected eye in an attempt to compensate for the outwardly rotated eye. Due to its long peripheral course around the midbrain CN IV is particularly susceptible to head trauma.

Last revised: March 22, 1998