Clinical NeuroscienceEffect of repetitive transcranial magnetic stimulation on the kynurenine pathway in stroke patientsNiimi, Masachikaa,,b; Ishima, Tamakic; Hashimoto, Kenjic; Hara, Takatoshia; Yamada, Naokia,,b; Abo, MasahiroaAuthor Information aDepartment of Rehabilitation Medicine, Jikei University School of Medicine bDepartment of Rehabilitation Medicine, Tokyo General Hospital, Tokyo cDivision of Clinical Neuroscience, Chiba University Center for Forensic Mental Health, Chiba, Japan Received 31 January 2020 Accepted 28 February 2020 Correspondence to Masachika Niimi, MD, PhD, Department of Rehabilitation Medicine, Jikei University School of Medicine, 3-25-8, Nishi-Shimbashi, Minato-Ku, Tokyo 105-8461, Japan, Tel: +81 3 3433 1111; fax: +81 3 3431 1206; e-mail: firstname.lastname@example.org NeuroReport: June 10, 2020 - Volume 31 - Issue 9 - p 629-636 doi: 10.1097/WNR.0000000000001438 Buy Metrics Abstract Objective Repetitive transcranial magnetic stimulation (rTMS) improves depressive symptoms and motor function in stroke patients. While metabolic derangement of the kynurenine pathway has been reported in stroke patients, the effect of rTMS on this pathway remains unknown. This study was performed to investigate the effect of rTMS on serum levels of kynurenine and tryptophan in stroke patients. Methods Sixty-two stroke patients received rTMS in addition to intensive rehabilitation and 33 stroke patients received intensive rehabilitation alone for 14 days. The rTMS involved low-frequency stimulation (at 1 Hz) of the primary motor cortex on the unaffected side of the cerebrum. The depressive state of the patients was evaluated with the Beck Depression Inventory (BDI) before and after treatment. Motor function of the patients was evaluated with Fugl-Meyer Assessment (FMA). Serum levels of kynurenine and tryptophan levels were also measured before and after treatment. Results The serum tryptophan level decreased in the group receiving rTMS to the right brain and increased in the group receiving rTMS to the left brain. The serum kynurenine/tryptophan ratio was elevated in the group receiving rTMS to the right brain. The BDI indicated improvement of depressive symptoms in the rehabilitation alone group and the group receiving rTMS to the right brain plus rehabilitation. The FMA improved in all groups. Conclusions The effect of low-frequency rTMS on the kynurenine pathway may differ depending on whether it is applied to the right or left cerebral hemisphere. Copyright © 2020 Wolters Kluwer Health, Inc. All rights reserved.