A Rare Case of Cluster Headache Occurring Exclusively During Sleep Without Autonomic Symptoms and Agitation: A Case Report and Literature Review.

As a primary headache disorder, cluster headache (CH) is a severe unilateral headache that recurs at certain times of the year, such as during season changes. It is characterized by autonomic symptoms, such as ipsilateral lacrimal and nasal discharge, as well as an inability to stay still during headache attacks. We report a rare case of CH in a 67-year-old male who presented with a severe right-sided headache lasting 30 minutes to one hour and occurring only during sleep. The headache resolved within five minutes after the subcutaneous injection of sumatriptan and was not accompanied by any autonomic symptoms or clear agitation.