We report the case of a patient suffering from migraine without aura since childhood who, at the age of 58 years, developed cluster headache (CH) attacks. This second type of headache was related to an aneurysm of the anterior communicating artery (ACoA) whose bursting caused subarachnoid haemorrhage. The aneurysm's clipping made the cluster headache subside and there was no recurrence for almost four years. However, nine months after haemorrhage, the patient experienced new migraine without aura attacks. As a pathogenetic interpretation of this secondary cluster headache, we discuss the possible role of pericarotid sympathetic nerves in cluster headache attacks. We suggest that the surgical dissection of the pericarotid sympathetic fibres could prevent the onset of the cluster headache attacks by cutting part of the circuit underlying it.