[Primary new daily persistent headache (NDPH): clinical characteristics of forty-three cases in Japan].

Although the primary chronic daily headache is subdivided into chronic migraine, chronic tension-type headache, hemicrania continua, and new daily persistent headache (NDPH), the characteristics of NDPH have not been well studied in Japan. The purpose of this study is to investigate the clinical characteristics of the primary NDPH. Twenty-one men and twenty-two women with primary NDPH, aged 14 to 73 years were diagnosed at Toyonaka Municipal Hospital from November 1997 to April 2003. Age of the onset ranged from 13 to 73 years (mean, 34.8). The onset of headache occurred in relation to a stressful life event in 16%, a systemic infection in 12% and an extracranial surgery in 7%. Any precipitating events could not be identified in approximately two-third of patients (65%). Quality of the headache was described as dull and/or pressure-like sensation in 91%, throbbing and/or pulsating sensation in 28%. NDPH needs further study, because it appears to be one of the most refractory headaches.