Chiari I Malformation: A Missed Diagnosis

Chiari I malformation is a complex congenital malformation of the hindbrain, characterized by herniation of the cerebellar tonsils through the foramen magnum into the cervical spinal canal. There may be mild caudal displacement and flattening or kinking of the medulla with an associated small posterior fossa. We present a case of a 30 year old man who presented with a 2 year history of worsening nystagmus and ataxia with associated occipital headache and diplopia. Examination showed a young man with horizontal and vertical nystagmus, he had truncal ataxia and Rhomberg’s sign was positive. Diagnosis was missed by several clinicians during the 2 year period. Repeated brain CT scans were normal. Brain MRI confirmed the diagnosis of Chiari I malformation and cervical syringomyelia. He had decompressive occipital craniectomy durotomy and duroplasty. The patient recovered fully from ataxia headache and diplopia but still has residual nystagmus.