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January 8, 2014: Eight-and-a-half syndrome

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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. [1]  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. [2]

References

  1. Fisher CM. Some neuro-ophthalmological observations. J Neurol Neurosurg Psychiatry. 1967; 30: 383-92.
  2. 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

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