One and a half syndrome
| One and a half syndrome | |
|---|---|
| Other names | On-and-a-half syndrome |
 | |
| Diagram of normal eye movement compared to left one-and-a-half syndrome (i.e. left lateral gaze palsy, with left Internuclear ophthalmoplegia (inability to adduct)) | |
| Causes |
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| Differential diagnosis |
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The one and a half is also present when the eye on the opposite side of the lesion is abducted. Convergence is classically spared as cranial nerve III (oculomotor nerve) and its nucleus is spared bilaterally.
Causes
Causes of the one and a half syndrome include
Anatomy
The syndrome usually results from single unilateral lesion of the paramedian pontine reticular formation and the ipsilateral medial longitudinal fasciculus. An alternative anatomical cause is a lesion of the abducens nucleus (VI) on one side (resulting in a failure of abduction of the ipsilateral eye and adduction of the contralateral eye = conjugate gaze palsy towards affected side), with interruption of the ipsilateral medial longitudinal fasciculus after it has crossed the midline from its site of origin in the contralateral abducens (VI) nucleus (resulting in a failure of adduction of the ipsilateral eye).
Treatment
There have been cases of improvement in extra-ocular movement with botulinum toxin injection.[4][5] Cases related to multiple sclerosis sometimes subside with adequate treatment. [3]
See also
References
- S2CID 35636994.
- ISBN 978-0-7817-9121-2.
- ^ PMID 35506717.
- PMID 12812899.
- ^ "Botulinum toxin injections". www.aesthetika.co.uk. Retrieved 30 August 2015.