Fourth nerve palsy affects the superior oblique muscle, leading to vertical or oblique double vision. It may be congenital or acquired from trauma, microvascular disease, or other neurological causes.
Symptoms and signs
Patients often adopt head postures to minimise diplopia.
- Vertical diplopia worse on looking down and in, such as reading or stairs
- Hypertropia of the affected eye and excyclotorsion
- Head tilt away from the affected side in long-standing cases
- Often decompensation of a congenital palsy in adulthood
Treatment
Management aims to restore comfortable single vision.
- Prism glasses to realign images in mild or stable cases
- Observation for spontaneous recovery in microvascular palsies
- Strabismus surgery for persistent or large deviations
- Neurological evaluation if cause is unclear or associated with other signs
