January 8, 2014: Eight-and-a-half syndrome
January 8, 2014
One-and-a-half syndrome (OHS) refers to horizontal gaze palsy (one) with intranuclear ophthalmoplegia (half) due to a lesion of the paramedian pontine reticular formation (PPRF) and medial longitudinal fasciculus.  The facial nucleus lies adjacent to the PPRF and gives rise to cranial nerve VII (CN7) which courses through the PPRF before circling the abducens nucleus and exiting the brainstem. A lesion from a stroke, multiple sclerosis, etc., at this junction can result in ipsilateral OHS plus ipsilateral lower motor neuron facial palsy (CN 7 + 1-1/2) resulting in Eight-and-a-half syndrome. 
- Fisher CM. Some neuro-ophthalmological observations. J Neurol Neurosurg Psychiatry. 1967; 30: 383-92.
- Eggenberger E. Eight-and-a-Half Syndrome: One-and-a-Half Syndrome Plus Cranial Nerve VII Palsy. J Neuro-ophthalmology. 1998; 18: 114-116.
Submitted by: Robert K. Mannel, MD, Resident, University of Florida-Jacksonville
Dr. Mannel reports no disclosures