Cranial Nerve IV, also known as the trochlear nerve, is one of the twelve cranial nerves in the human body. It is primarily responsible for controlling the movement of the superior oblique muscle, which helps in rotating the eye downward and laterally. This nerve is unique because it is the only cranial nerve that emerges from the dorsal aspect of the brainstem. The trochlear nerve is a motor nerve, meaning it carries signals from the brain to the muscles. Damage to this nerve can lead to double vision and difficulty in moving the affected eye, a condition known as trochlear nerve palsy. Proper functioning of Cranial Nerve IV is essential for coordinated eye movement.