Recurrent headache mimicking cluster headache: a diagnostic challenge.

A 37-year-old man presented with recurrent, severe left-sided headaches occurring at the same time each evening, accompanied by ipsilateral lacrimation, conjunctival injection, and nasal congestion. The clinical features were suggestive of cluster headache (CH), but poor response to high-flow oxygen and triptans raised concern for a secondary cause. Neuroimaging revealed an ethmoid sinus mucocele with adjacent bone remodeling, mimicking trigeminal autonomic cephalalgia. Surgical drainage led to complete symptom resolution, suggesting a secondary headache etiology. This case highlights the need to consider structural causes in atypical or treatment-resistant headache presentations and the importance of neuroimaging in accurate diagnosis and management.