A Rare Case Report of Eight Syndrome Secondary to Syringomyelia Associated with Type I Chiari Malformation.

Eight syndrome is defined as the combination of a unilateral conjugate gaze palsy and ipsilateral seventh cranial nerve palsy. It may occur as a result of demyelinating, vascular, infectious, or compressive lesions of the brainstem localized to the caudal pontine tegmentum. A 43-year-old woman was admitted to our clinic with complaints of headache, inability to look to the left, and weakness on the left side of her face. The complaints had begun abruptly about a month before her admission. Suboccipital decompression surgery for type I Chiari malformation had been performed 10 years earlier. Neuro-ophthalmological examination revealed left-sided horizontal gaze palsy and anisocoria. Cranial and cervical magnetic resonance images revealed cerebellar tonsillar herniation and syringomyelia, the latter of which was considered to be the cause of eight syndrome. No interventions were performed, and periodic follow-up was advised on neurosurgical consultation. Left gaze palsy and facial palsy recovered almost completely in three months, while the anisocoria persisted. Syringomyelia should be considered among the causes of horizontal gaze palsy plus ipsilateral seventh nerve palsy, termed as eight syndrome. Clinical suspicion and appropriate radiological examination can aid in the diagnosis.