Unit 2: Visual field defects, double vision & optic disc swelling
2: Diplopia (Double Vision)
6th (Abducent) nerve
The 6th (Abducent) Cranial nerve supplies the Lateral Rectus muscle.
In 6th nerve palsy there is failure in abduction.
The patient suffers horizontal diplopia which is greater when looking to the affected side.
A right 6th nerve palsy. The right eye fails to abduct when the patient looks to the right.
Image credit: Reproduced from A case of orbital myositis associated with rheumatoid arthritis, S Nabili, D W McCarey, B Browne, H A Capell Ann Rheum Dis 2002;61:938-939. BMJ Publishing Group Ltd
Aetiology
Adults
- Hypertension or diabetes in adults >50 years of age
- Multiple Sclerosis
- Neoplasm
- Head trauma
- Infection
- Raised intracranial pressure
Children
- Transient 6th nerve may occur in neonates
- Benign causes may occur 1-3 weeks after viral infection
Symptoms
- Horizontal diplopia greater looking to the affected side at distance.
- May be constant
Signs
- May have a head turn to the same side
- Limitation in abduction
- Eso deviation on cover test
Investigations
- Orthoptic investigation
- Blood tests
- MRI
Management
- Prisms or surgery if not spontaneously resolving.
Failure of abduction in right 6th Nerve Palsy
Image credit: Reproduced from Not a microvascular sixth nerve palsy, H Steel, J Aram, T Wilhelm, S J Hickman, L Ginsberg Pract Neurol 2007;7:400-404. BMJ Publishing Group Ltd
