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Updated: Mar 8, 2026
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Assessing Binocular Central Visual Field and Binocular Eye Movements in a Dichoptic Viewing Condition
Published on: July 21, 2020
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Blood, brain and binocular vision.
Egle Rostron1, Mary Polly Dickerson1, Gregory Heath2
1Ophthalmology Department, St James Hospital, Leeds, UK.
BMJ Case Reports
|February 1, 2017
Summary
A rare neurological condition, the eight-and-a-half syndrome, was diagnosed in a patient with polycythaemia vera. Prompt treatment of the blood disorder led to significant recovery of vision and facial nerve function.
Area of Science:
- Neuroscience
- Hematology
- Ophthalmology
Background:
- The eight-and-a-half syndrome is a rare neurological disorder characterized by horizontal gaze palsy and ipsilateral facial nerve palsy.
- It typically results from a lesion in the pons, affecting the abducens nucleus and facial nerve fascicles.
Observation:
- A 51-year-old man presented with sudden onset horizontal double vision and right facial weakness.
- Ocular motility examination revealed a right horizontal gaze palsy and a lower motor neuron (LMN) facial nerve palsy, consistent with the eight-and-a-half syndrome.
- Diffusion-weighted MRI confirmed a pontine infarct affecting the horizontal gaze center and VIIth cranial nerve fasciculus.
Findings:
- Further investigations revealed an underlying diagnosis of polycythaemia vera, a myeloproliferative neoplasm.
- The patient's neurological symptoms were attributed to this undiagnosed blood dyscrasia.
Implications:
- Treatment with regular venesection led to complete resolution of ocular motility dysfunction and improvement in the LMN facial nerve palsy.
- This case highlights the importance of considering systemic conditions, such as polycythaemia vera, in the differential diagnosis of brainstem syndromes.
- Early diagnosis and management of polycythaemia vera can significantly improve neurological outcomes in patients presenting with the eight-and-a-half syndrome.
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