Hypnic headache: Report of two cases

Hypnic headache constitutes one rare type of primary short-lasting headache related to sleep. The authors describe two cases of hypnic headache that had a very good resp onse to lithium carbonate. Although these two cases do not fulfill the prop osed criteria for hypnic headache, as the pain was not bilateral, and, in c ase 2, it had a longer duration than previously described, we believe that the very good response to lithium carbonate favors this diagnosis. We believe that it is important to consider a diagnosis of hypnic headache because of the remarkable response to lithium carbonate shown by some patie nts with this condition.