Two symptomatic cases of cluster headache associated with internal carotid artery dissection.

Cluster headache is a clinical entity characterised by strictly unilateral head pain attacks accompanied by ipsilateral autonomic phenomena. We report two patients who had pain episodes mimicking cluster headache attacks, and who experienced a total or partial Horner's syndrome ipsilaterally to pain, persisting for 48 h after the last attack. A dissection of the ipsilateral internal carotid artery at the extra-intracranial passage was present in both cases. These cases highlight the need for extensive neuroradiological investigation in cluster headache patients when atypical features are present.