Basilar artery migraine is a distinctive disorder characterized by recurrent occipital headache with typical migrainous phenomena in conjunction with a variety of symptoms referable to a transient dysfunction of the brainstem, the cerebellum and the occipital lobes. Impairment of consciousness is a common feature but is usually too brief to be captured by electroencephalography. Here we report an unusual case of basilar artery migraine with prolonged attacks of impaired consciousness lasting more than two Weeks, thus allowing electroencephalographic follow-up. In the acute stage, EEG showed marked generalized slow wave delta activity. After the attack, both the electroencephalographic and clinical findings subsided within the following weeks.