Headache and Chiari I malformation: clinical presentation, diagnosis, and controversies in management.

The Chiari I malformation is a cerebellar anomaly of uncertain origin, defined in part as tonsillar herniation of at least 3 to 5 mm below the foramen magnum; it is associated with crowding of the craniocervical junction. It is the most frequent of the Chiari malformations and is associated with headaches, syringohydromyelia, and hydrocephalus. The clinical manifestations are related to direct compression of neural tissues and abnormal cerebrospinal fluid dynamics. Common presentation is in adulthood, but there is increasing recognition in childhood. Incidental magnetic resonance imaging discovers Chiari I in one third of patients who do not have clinical symptoms. Headaches in the occipital-suboccipital region or those that are of cough-type suggest symptomatic Chiari I malformation. Suboccipital craniectomy is performed for patients with Chiari I malformation who have neural compression syndromes of the brainstem and spinal cord, select headache types, and other uncommon conditions that are not the topic of this review.