Carotid dissection presenting as a prolonged cluster-like headache in a patient with episodic cluster headache

We present a patient with known episodic cluster headache, who presented with cluster-like headache in the course of internal carotid artery dissection (ICAD) and discuss possible pathophysiological links between the two diseases. It is well known that cluster-like headache could be the presenting symptom of ICAD. However, ICAD occurring in a patient with a known episodic cluster headache was only once previously described. In the end of the manuscript, we propose red flags to help clinicians differentiate between primary cluster headache and cluster-like attacks masking underlying ICAD. Finally, we raise the question whether at least some proportion of those patients with cluster headache and Horner syndrome previously classified as a primary headache disorder might have been secondary cases to ICAD.