Hypnic Headache Due to Hypoglycemia: A Case Report.

Hypnic headache (HH) is a rare primary headache disorder and pathophysiology is still poorly understood. It is considered a chronobiological disorder in almost all published cases. Few secondary cases have been described so far. We report a case of a 64-year-old woman presenting headaches exclusively during sleep and fulfilling the diagnostic criteria for HH, but a 72-hour glucose monitoring showed hypoglycemia episodes related to the onset of headaches. To our knowledge, this is the first report of symptomatic HHs associated with hypoglycemia and it suggests direct evidence of HH due to a metabolic disorder.