Introduction
Ketogenic diet (KD) is a valid treatment for drug-resistant epilepsy, recently proposed as effective also in migraine. Hitherto, no data are available about KD effects on cluster headache (CH), a severe form of primary headache, characterized (similarly to migraine) by a trigemino-vascular activation. Prophylaxis drug-resistant patients have a great need for care and could seek help in invasive treatments and/or alternative drugs, such as illegal substances. Here we performed a prospective observational study of the potential beneficial ketogenesis-induced effects on CH, studying a group of consecutive drug-resistant CH patients.