Patients with sudden onset headache not meeting the criteria of the International Headache Society for new daily persistent headache. How to classify them?

We conducted a retrospective analysis of the records of 1348 patients regularly treated at the headache clinic of Department of Neurology of Santa Casa de São Paulo, Brazil. Sixty-two patients reported history of daily and persistent headache. From the 62 patients selected, only 21 (group 1) could be diagnosed with new daily-persistent headache (NDPH) according to the International Headache Society (HIS) 2004 criteria. The 41 remaining patients (group 2) could not be diagnosed with NDPH according to IHS-2004 once they presented two or more migraine attack-related symptoms, such as: nausea, photophobia, phonophobia and vomiting, in different combinations. It was not possible to classify them in groups 1 to 4 of primary headaches either. How to classify them? We suggest that the criteria are revised. And one way we can classify them, would be the subdivision: NDPH with migraine features and without migraine features that would allow the inclusion of all individuals present who has a daily and persistent headache from the beginning.