Trigeminal Autonomic Cephalalgias (TACs) – Hemicrania Continua

Hemicrania continua (HC) is a relatively rare primary headache disorder characterized by unilateral pain and an exquisite response to indomethacin. Since the term was introduced in 1984, more than 100 cases have been reported in the literature. Useful information regarding the pathophysiology comes from functional imaging that suggests a role for subcortical neural structures. A positron emission tomography (PET) study in HC patients showed activation of the contralateral posterior hypothalamus, the ipsilateral dorsal pons, and ipsilateral ventral midbrain. Taken together with the unique effect of indomethacin to block the pain, the data point to the classification of HC as a unique syndrome that belongs to trigeminal autonomic cephalalgias (TACs).