Assessing regional intracortical myelination in schizophrenia spectrum and bipolar disorders using the optimized T1w/T2w-ratio

• Published in: Psychological medicine Vol. 54; no. 10; pp. 1 - 2379
• Main Authors: Jørgensen, Kjetil Nordbø, Nerland, Stener, Slapø, Nora Berz, Norbom, Linn B, Mørch-Johnsen, Lynn, Wortinger, Laura Anne, Barth, Claudia, Andreou, Dimitrios, Maximov, Ivan I, Geier, Oliver M, Andreassen, Ole A, Jönsson, Erik G, Agartz, Ingrid
• Format: Journal Article
• Language: English
• Published: England Cambridge University Press 01.07.2024
• Subjects: Age; Age differences; Antipsychotics; Bipolar disorder; Brain research; Cerebral cortex; Chlorpromazine; Cortex; Dosage; Drugs; Entorhinal cortex; Magnetic resonance imaging; Medical diagnosis; Medicin och hälsovetenskap; Mental disorders; Myelination; Normalization; Pathophysiology; Patients; Psychosis; Psychotic symptoms; Psychotropic drugs; Regional variations; Regions; Regression analysis; Schizophrenia; Temporal lobe; Temporal lobes; cerebral cortex; myelin sheath; schizophrenia; antipsychotic agents; psychotic disorders
• ISSN: 0033-2917; 1469-8978; 1469-8978
• DOI: 10.1017/S0033291724000503

Dysmyelination could be part of the pathophysiology of schizophrenia spectrum (SCZ) and bipolar disorders (BPD), yet few studies have examined myelination of the cerebral cortex. The ratio of T1- and T2-weighted magnetic resonance images (MRI) correlates with intracortical myelin. We investigated the T1w/T2w-ratio and its age trajectories in patients and healthy controls (CTR) and explored associations with antipsychotic medication use and psychotic symptoms. Patients with SCZ ( = 64; mean age = 30.4 years, s.d. = 9.8), BPD ( = 91; mean age 31.0 years, s.d. = 10.2), and CTR ( = 155; mean age = 31.9 years, s.d. = 9.1) who participated in the TOP study (NORMENT, University of Oslo, Norway) were clinically assessed and scanned using a General Electric 3 T MRI system. T1w/T2w-ratio images were computed using an optimized pipeline with intensity normalization and field inhomogeneity correction. Vertex-wise regression models were used to compare groups and examine group × age interactions. In regions showing significant differences, we explored associations with antipsychotic medication use and psychotic symptoms. No main effect of diagnosis was found. However, age slopes of the T1w/T2w-ratio differed significantly between SCZ and CTR, predominantly in frontal and temporal lobe regions: Lower T1w/T2w-ratio values with higher age were found in CTR, but not in SCZ. Follow-up analyses revealed a more positive age slope in patients who were using antipsychotics and patients using higher chlorpromazine-equivalent doses. While we found no evidence of reduced intracortical myelin in SCZ or BPD relative to CTR, different regional age trajectories in SCZ may suggest a promyelinating effect of antipsychotic medication.