A differential diagnosis in postural headache: herniation of a giant posterior fossa arachnoid cyst.

The causes of postural headache are usually associated with low intracranial pressure. However, there are still rare causes of posture-related headaches that are not associated with low intracraninal pressure and caused by pathologic processes. Herein, we report a patient with giant posterior fossaarachnoid cyst herniating below the level of foramen magnum presenting with postural headache, which has not been described previously in the literature. Emergency physicians should be aware that posterior fossa arachnoid cysts should be considered one of the differential diagnoses in patients with postural headache.