sixth nerve palsy
Also called abducens nerve palsy, abducens palsy, lateral rectus palsy, CN VI palsy, CN 6 palsy
A sixth nerve palsy is weakness of the lateral rectus, the only muscle the abducens nerve supplies. It produces an esotropia in primary position that is largest on gaze toward the affected side and at distance, with limited abduction, normal adduction and a pupil that is never involved.1,3
The unopposed medial rectus turns the eye inward. Horizontal double vision is worse for distant targets and worse on gaze toward the weak muscle, and many patients restore single vision by turning the face toward the side of the palsy.2
Divergence insufficiency also causes esotropia at distance, but the deviation is the same in every direction of gaze, whereas a palsy is worst in the field of the weak muscle. The long course of the sixth nerve inside the skull makes it the most vulnerable of the ocular motor nerves: raised intracranial pressure, fracture of the skull base and vascular disease are the usual adult causes, and children may develop a palsy after a viral illness that clears in about six weeks.4 A bilateral palsy demands exclusion of raised intracranial pressure.1
More detail
In Duane syndrome the globe retracts and the lid fissure narrows when the eye turns inward, and in infantile esotropia with cross fixation abduction is possible once the other eye is covered.5 When the palsy is long-standing the medial rectus tightens into a contracture and forced ductions become positive.3
Sources (5)
- Kanski, Clinical Ophthalmology (2024), ch. 19
- Liu, Volpe and Galetta, Neuro-Ophthalmology, ch. 15
- Yanoff and Duker, Ophthalmology (2023), ch. 9
- Pickwell's Binocular Vision Anomalies, ch. 17
- von Noorden and Campos, Binocular Vision and Ocular Motility, ch. 20
Reviewed October 2026