Acute Visual Loss Secondary to Arnold Chiari Type I Malformation Completely Resolving After Decompressive Posterior Fossa Surgery.

We describe the case of a 22-year-old woman of southeast-Asian origin, presenting with unilateral sudden visual loss after a self-healing hearing loss a week before. Ophthalmological examination showed visual acuity of light perception in the left eye, mild RAPD, normal ocular motility and an elevated optic disc with indistinct margins. Neurological examination showed no acute pathology and brain CT-MRI imaging revealed a small-almost subclinical-herniation of the cerebellar tonsils. As investigation eliminated every other infectious or inflammatory cause of papillitis, neurosurgical intervention was proposed. The patient underwent an uncomplicated occipital craniotomy with posterior fossa decompression and had a favorable revolution with regression of papilledema and a fully recovering visual acuity that reached 20/20. Chiari malformation type I refers to an abnormality of the posterior fossa that has a smaller volume than normal, leading to the herniation of cerebellar tonsils, at least 5 mm below the foramen magnum. The occurrence of papilledema associated with Chiari malformation type 1 is rare. Chiari malformation has, until today, mainly been studied among children populations, usually with a poor visual acuity recovery. The originality of our case report consists in the description of an adult patient case showing unilateral, unusual ophthalmological findings and complete recovery after surgical treatment.