<qa>  What is one of the most disabling medical illnesses?Chronic migraine and chronic cluster headaches are among the most disabling medical illnesses, inflicting severe functional impairment. These headache subtypes are particularly resistant to current treatment modalities, with the majority of chronic migraine patients continuing to experience frequent or near-daily headaches despite aggressive, multidisciplinary, and multimodal therapy. The refractory nature of these illnesses and the level of devastation they inflict on the lives of their victims has motivated the pursuit of novel treatment approaches. 