Plain Language Summary Publication: Hyperactivity of the medial thalamus in patients with photophobia‐associated migraine

Main Finding: The inside of the thalamus (gray matter structure in the brain) may be associated with the development of continuous photophobia, or constant glare, in patients with migraine. Motivation: Migraine attacks are often accompanied by photophobia. Some patients with migraine experience constant glare, or photophobia, even during headache-free intervals. Patients with constant photophobia have various inconveniences in their daily lives. We aimed to examine functional changes in the brains of patients with migraine who have photophobia. Methods: We examined the degree of photophobia in daily life for each patient with photophobia using a questionnaire. We also estimated the photophobia threshold by gradually increasing lighting brightness. We measured brain activity using positron emission tomography in patients with migraine with and without constant photophobia compared to healthy participants. Furthermore, we examined the relationship between brain activity and the degree of photophobia in daily life or the photophobia threshold. Results: Compared to the healthy group, we observed increased activity in both sides of the thalamus in patients with migraine with and without glare. Moreover, the inside of the thalamus was more active in patients with migraine with constant photophobia than in those without photophobia. We found a positive correlation between thalamic activity and the degree of photophobia in daily life. We also found a correlation between thalamic activity and photophobia threshold. Implications: We found that thalamic activity was increased in patients with migraine with or without constant photophobia. The inside of the thalamus may be associated with the development of constant photophobia in patients with migraine. The degree of photophobia and photophobia threshold are thought to influence brain activity in patients with migraine. Study concept and design: Yukihisa Suzuki and Kenji Ishii. Acquisition of data: Yukihisa Suzuki and Kenji Ishii. Analysis and interpretation of data: Yukihisa Suzuki, Motohiro Kiyosawa, and Kenji Ishii. Drafting of the manuscript: Yukihisa Suzuki. Revising it for intellectual content: Yukihisa Suzuki and Kenji Ishii. Final approval of the completed manuscript: Yukihisa Suzuki, Motohiro Kiyosawa, Masato Wakakura, and Kenji Ishii. The authors thank all the participants for volunteering their time and the staff of the Tokyo Metropolitan Institute of Gerontology for the production of fluorodeoxyglucose and for assisting the participants undergoing positron emission tomography. There is no funding/support associated with this study. Yukihisa Suzuki, Motohiro Kiyosawa, Masato Wakakura, and Kenji Ishii declare no conflicts of interest.