Hindbrain hernia headache.

In six patients with episodic, severe, and disabling headaches with specific characteristics and in whom clinical examination and CT scanning were normal the symptoms were due to hindbrain herniation into the foramen magnum with resulting craniospinal pressure dissociation. This syndrome may be recognised by eliciting the typical history. In all patients myelography showed hindbrain herniation or Arnold-Chiari deformity and surgical decompression of the foramen magnum produced complete resolution of the headaches.