Trochlear nerve palsy is a condition that affects the fourth cranial nerve, known as the trochlear nerve. This nerve controls the superior oblique muscle, which helps move the eye downward and outward. When this nerve is damaged or not functioning properly, it can lead to double vision and difficulty with eye movement, particularly when looking down. Symptoms of trochlear nerve palsy often include a noticeable head tilt, as individuals may try to compensate for the misalignment of their eyes. The condition can result from various causes, including trauma, vascular issues, or neurological disorders. Treatment may involve eye exercises, prisms, or, in some cases, surgery.