High-Altitude Headache Resolving After Self-Administration of Goreisan: A Case Report.

High-altitude headache (HAH) is the most common neurological manifestation of rapid ascent to high altitude and may occur independently or as part of acute mountain sickness (AMS). Although simple analgesics are commonly used for symptomatic treatment, evidence regarding alternative therapeutic options remains limited. Goreisan, a traditional Japanese Kampo medicine, has been reported to regulate body fluid homeostasis through aquaporin modulation and may influence cerebral fluid dynamics. However, to our knowledge, its use for HAH has not previously been reported. We herein describe a 34-year-old Japanese man with a history of migraine and hypertension, who developed a headache clinically consistent with HAH that resolved after oral administration of Goreisan. He developed a right unilateral headache approximately 90 minutes after rapid ascent from Lima (150 m) to Cusco, Peru (3,400 m). The clinical presentation was consistent with the International Classification of Headache Disorders, 3rd edition criteria for HAH, although an altitude-triggered migraine attack could not be completely excluded. Because no analgesics were available, he self-administered 2.5 g of Goreisan. The headache began to improve within 30 minutes, decreased from 4/10 to 1/10 on the Numerical Rating Scale within one hour, and resolved completely within two hours without additional medication. No recurrence occurred during the remainder of his 10-day stay, and he was able to undertake hiking activities the following day. Although improvement occurred temporally after Goreisan administration, spontaneous improvement or early acclimatization cannot be excluded, and causality cannot be established from this single case. This observation supports prospective evaluation of Goreisan in patients with HAH.