Œdème papillaire revelant une malformation d’Arnold Chiara type 1 : à propos d’un cas

Arnold Chiari malformation type 1 is defined as a herniation of the cerebellar tonsils into the foramen magnum of more than 5 mm. Symptoms are most commonly dominated by occipital headache, torticollis and sometimes swallowing disorders. Ophthalmologically abnormal convergences, oculomotor palsy and diplopia are the main clinical signs. We report the case of a 9 year old child, who presented with visual loss evolving since 6 months. Ophthalmologic examination showed visual acuity of 4/10 in both eyes, retained ocular motility and rotational nystagmus. The examination of the anterior segment of the eye showed megalocornea with no evidence of goniodysgenesis, iridodonesis associated with atrophy of the dilator muscle and microcoria with lazy photomotor reflex. Normal intraocular pressure was 14 mmHg. Ocular fundus examination, despite difficulties in performing it, objectified bilateral papilledema (stage II). General physical examination showed torticollis, scoliosis and a tetra-pyramidal syndrome. MRI showed Chiari malformation type I associated with hydrocephalus and syringomyelia. Neurosurgical intervention based on internal CSF drainage with occipitocervical osteo-dural decompression was proposed. The evolution was favorable with regression of clinical signs. Ophthalmologically, there was a regression of papilledema but visual acuity remained stationary. The occurrence of papilledema associated with Chiari malformation type 1 is rare, it has been only reported in 2% of symptomatic patients. Its pathophysiology is still poorly understood. The originality of our study consists in the association of cerebellar malformations with ocular malformations including megalocornea and microcoria which make ophthalmologic examination more difficult to perform.