What is a fourth nerve palsy?
The fourth cranial nerve innervates the superior oblique muscle so weakness of the muscle is also known as superior oblique palsy. The superior oblique muscle produces downward, outward and inward rotation (intorsion) of the eye. Therefore weakness of the muscle causes a reduction in depression of the eye and a relatively elevated position compared to the other eye. The eye also often rotates outward (extorsion) and slightly inward. The upward movement of the eye is typically the most noticeable feature. Palsy refers to a complete weakness of a muscle while a paresis is a partial weakness. This condition is usually unilateral (one eye) but can be bilateral (both eyes).
