White matter microstructural organizations in patients with severe treatment-resistant schizophrenia: A diffusion tensor imaging study.

Previous diffusion tensor imaging (DTI) studies have reported white matter alterations in patients with schizophrenia. Notably, one third of this population does not respond to first-line antipsychotics and is thus referred to as treatment-resistant schizophrenia (TRS). Despite potentially distinct neural bases between TRS and non-TRS, few studies have compared white matter integrity between these groups. In order to reflect clinical picture of TRS, we enrolled TRS patients who had severe symptoms. According to the consensus criteria for TRS. TRS was defined by severe positive symptomatology despite optimal antipsychotic treatment. Fractional anisotropy (FA), an index of white matter integrity, was examined by DTI and analyzed with tract-based spatial statistics in 24 TRS patients (mean PANSS = 108.9), 28 non-TRS patients (mean PANSS = 50.0), and 27 healthy controls (HCs) for group comparison. Additionally, correlation analyses were conducted between FA values and symptomatology. The TRS group had lower FA values in multiple tracts (cerebral peduncle, corona radiata, corpus callosum, external and internal capsules, posterior thalamic radiation, sagittal stratum, superior longitudinal fasciculus, tapetum, and uncinate fasciculus) compared to the HC group as well as the non-TRS group (p < .05; family-wise error-corrected), while no differences were found between the non-TRS and HC groups. In the TRS group, FA values in most of the tracts (other than the left anterior limb of internal capsule, left cerebral peduncle, and right uncinate fasciculus) were negatively correlated with the Positive and Negative Syndrome Scale total scores, and negative and general symptom scores. No such relationships were found in the non-TRS group. The identified white matter integrity deficits may reflect the pathophysiology of TRS.
Competing Interests: Declaration of Competing Interest YN has received a Grant-in-Aid for Young Scientists (KAKENHI), a research grant from Japan Agency for Medical Research and Development (AMED), an investigator-initiated clinical study grant from TEIJIN PHARMA LIMITED. YN also receives research grants from Japan Health Foundation, Meiji Yasuda Mental Health Foundation, Mitsui Life Social Welfare Foundation, Takeda Science Foundation, SENSHIN Medical Research Foundation, Health Science Center Foundation, Mochida Memorial Foundation for Medical and Pharmaceutical Research, and Daiichi Sankyo Scholarship Donation Program. He has received research supports from Otsuka Pharmaceutical, Shionogi, and Meiji Seika Pharma. YN also receives equipment-in-kind supports for an investigator-initiated study from Magventure Inc., Inter Reha Co., Ltd., Rogue Resolutions Ltd., and Miyuki Giken Co., Ltd. EP has received research support from an Ontario Graduate Scholarship (OGS), a Canadian Institutes of Health Research (CIHR) Canada Graduate Scholarship-Master's, a CIHR Vanier Canada Graduate Scholarship, and he currently receives research support from the Healthy Brains for Healthy Lives Postdoctoral Fellowship. MMC has received research funding from the Weston Brain Institute, Alzheimer's Association, and Michael J. Fox Foundation. He is currently receiving support from the Canadian Institutes of Health Research, National Sciences and Engineering Research Council of Canada, and McGill University's Healthy Brains for Healthy Lives Initiative. AG-G has received research support from the following external funding agencies: CIHR, U.S National Institutes of Health, Ontario Mental Health Foundation, National Alliance for Research on Schizophrenia and Depression, Mexico Instituto de Ciencia y Tecnología del Distrito Federal, Consejo Nacional de Ciencia y Tecnología, Ministry of Economic Development and Innovation of Ontario, Ontario Academic Health Science Center Alternate Funding Plan Innovation Fund, and W. Garfield Weston Foundation. HU has received grants from Eisai, Otsuka Pharmaceutical, Dainippon-Sumitomo Pharma, Mochida Pharmaceutical, Meiji-Seika Pharmaceutical, and Novartis; speaker's honoraria from Otsuka Pharmaceutical, Eli Lilly, Shionogi, Pfizer, Yoshitomi Yakuhin, Dainippon-Sumitomo Pharma, Meiji-Seika Pharma, MSD, and Janssen Pharmaceutical; and advisory panel payments from Dainippon-Sumitomo Pharma within the past three years. MM has received research support from Japan Society for the Promotion of Science and grants or speaker's honoraria from Daiichi Sankyo, Dainippon-Sumitomo Pharma, Eisai, Eli Lilly, Fuji Film RI Pharma, Janssen Pharmaceutical, Mochida Pharmaceutical, MSD, Nippon Chemipher, Novartis Pharma, Ono Yakuhin, Otsuka Pharmaceutical, Pfizer, Takeda Yakuhin, Tsumura, and Yoshitomi Yakuhin within the past three years. SN has received fellowship grants from CIHR, Japan Research Foundation for Clinical Pharmacology, Naito Foundation, Takeda Science Foundation, Uehara Memorial Foundation, and Daiichi Sankyo Scholarship Donation Program within the past three years. SN has also received research supports, manuscript fees or speaker's honoraria from Dainippon Sumitomo Pharma, Meiji-Seika Pharma, Otsuka Pharmaceutical, Shionogi, and Yoshitomi Yakuhin within the past three years. Other authors have no financial or other relationship relevant to the subject of this manuscript.
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