Update in the understanding of new daily persistent headache.

Background Accumulating evidence suggests various specific triggers may lead to new daily persistent headache (NDPH)-like presentations, suggesting that new daily persistent headache is a heterogenous syndrome, and challenging the concept that new daily persistent headache is a primary headache disorder.Method We searched the PubMed database up to August 2022 for keywords including persistent daily headache with both primary and secondary etiologies. We summarized the literature and provided a narrative review of the clinical presentation, diagnostic work-ups, possible pathophysiology, treatment response, and clinical outcomes.Results and conclusion New daily persistent headache is a controversial but clinically important topic. New daily persistent headache is likely not a single entity but a syndrome with different etiologies. The issue with past studies of new daily persistent headache is that patients with different etiologies/subtypes were pooled together. Different studies may investigate distinct subsets of patients, which renders the inter-study comparison, both positive and negative results, difficult. The identification (and removal) of a specific trigger might provide the opportunity for clinical improvement in certain patients, even when the disease has lasted for months or years. Nonetheless, if there is a specific trigger, it remains unknown or unidentified for a great proportion of the patients. We need to continue to study this unique headache population to better understand underlying pathogenesis and, most importantly, to establish effective treatment strategies that hopefully resolve the continuous cycle of pain.