Headache in Chiari Malformation.

Headache is a common symptom in patients with Chiari I malformation (CMI), characterized by 5 mm or greater cerebellar tonsillar herniation below foramen magnum. Radiologists should be aware of the different types of headaches reported by CMI patients and which headache patterns are distinctive features of the diagnosis. A methodical imaging strategy is required to fully assess a CMI patient to exclude secondary causes of tonsillar herniation such as intracranial hypotension or associated conditions such as syrinx. Both anatomic and physiologic imaging can help determine if headaches are CMI associated, and assist clinicians in therapeutic decision making.