Introduction: Hypnic headache is a rare condition, since less than 150 cases have been reported to date. The second edition of the International Headache Classification (IHC2) has set out the diagnostic criteria of this condition, although some of them can be considered excessively strict.
Aims: To present a series of 13 new cases of hypnic headache that were dealt with in the headache unit of a tertiary hospital and to analyse how well they fit the diagnostic criteria of the IHC2.
Patients and methods: Between January 2008 and January 2011, 13 patients (11 females and 2 males), out of a total of 1180 who visited the above-mentioned service (1.1%), were diagnosed with hypnic headache. The characteristics of the pain and the response to prophylactic treatment were evaluated.
Results: The age of onset of the clinical signs and symptoms was 56.7 ± 9.3 years (range: 40-76 years); in two patients (15.4%) it was prior to the age of 50. The number of symptomatic nights per month was 14.5 ± 7.6 (range: 5-25); in seven cases (53.8%) the number was less than 15 nights. All the patients presented one single episode per night, with a mean duration of 53.8 ± 24.6 minutes (range: 25-120 minutes). Thirty point seven per cent of the patients did not describe their pain as dull. Sixty-one point five per cent satisfied all the IHC2 diagnostic criteria.
Conclusions: The characteristics of our series were similar to others that have recently been published. We propose that the next criteria in the IHC should include the possibility of the pain not being dull and that it occurs on fewer than 15 nights per month. The lower limit for the age of onset could be reduced to 40 years.