title: Myelin vs axon abnormalities in white matter in bipolar disorder.
abstract: White matter (WM) abnormalities are among the most commonly reported neuroimaging findings in bipolar disorder. Nonetheless, the specific nature and pathophysiology of these abnormalities remain unclear. Use of a combination of magnetization transfer ratio (MTR) and diffusion tensor spectroscopy (DTS) permits examination of myelin and axon abnormalities separately. We aimed to examine myelination and axon geometry in euthymic patients with bipolar disorder with psychosis (BDP) by combining these two complementary noninvasive MRI techniques. We applied a combined MRI approach using MTR to study myelin content and DTS to study metabolite (N-acetylaspartate, NAA) diffusion within axons in patients with BDP (n=21) and healthy controls (n=24). Data were collected from a 1 × 3 × 3-cm voxel within the right prefrontal cortex WM at 4 Tesla. Clinical and cognitive data were examined in association with MTR and DTS data. MTR was significantly reduced in BDP, suggesting reduced myelin content. The apparent diffusion coefficient of NAA did not differ from healthy controls, suggesting no changes in axon geometry in patients with BDP. These findings suggest that patients with BDP exhibit reduced myelin content, but no changes in axon geometry compared with controls. These findings are in contrast with our recent findings, using the same techniques, in patients with schizophrenia (SZ), which suggest both myelination and axon abnormalities in SZ. This difference may indicate that alterations in WM in BDP may have unique causes and may be less extensive than WM abnormalities seen in SZ.
authors.affiliation: 1] McLean Hospital Schizophrenia and Bipolar Disorder Program, Belmont, MA, USA [2] McLean Hospital, Harvard Medical School, Boston, MA, USA.
authors.forename: Kathryn E
authors.initials: KE
authors.lastname: Lewandowski
authors.affiliation: 1] McLean Hospital Schizophrenia and Bipolar Disorder Program, Belmont, MA, USA [2] McLean Hospital, Harvard Medical School, Boston, MA, USA.
authors.forename: Dost
authors.initials: D
authors.lastname: Ongür
authors.affiliation: McLean Hospital Schizophrenia and Bipolar Disorder Program, Belmont, MA, USA.
authors.forename: Sarah H
authors.initials: SH
authors.lastname: Sperry
authors.affiliation: 1] McLean Hospital Schizophrenia and Bipolar Disorder Program, Belmont, MA, USA [2] McLean Hospital, Harvard Medical School, Boston, MA, USA.
authors.forename: Bruce M
authors.initials: BM
authors.lastname: Cohen
authors.affiliation: McLean Hospital Schizophrenia and Bipolar Disorder Program, Belmont, MA, USA.
authors.forename: Selma
authors.initials: S
authors.lastname: Sehovic
authors.affiliation: McLean Hospital Schizophrenia and Bipolar Disorder Program, Belmont, MA, USA.
authors.forename: Jacqueline R
authors.initials: JR
authors.lastname: Goldbach
authors.affiliation: 1] McLean Hospital Schizophrenia and Bipolar Disorder Program, Belmont, MA, USA [2] McLean Hospital, Harvard Medical School, Boston, MA, USA.
authors.forename: Fei
authors.initials: F
authors.lastname: Du
mesh_terms: D000328:Adult; D001224:Aspartic Acid / Q000031:analogs & derivatives / Q000378:metabolism; D001369:Axons / Q000378:metabolism / Q000473:pathology*; D001714:Bipolar Disorder / Q000150:complications / Q000378:metabolism / Q000473:pathology*; D056324:Diffusion Tensor Imaging; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D017397:Prefrontal Cortex / Q000378:metabolism / Q000473:pathology*; D066244:Proton Magnetic Resonance Spectroscopy; D011569:Psychiatric Status Rating Scales; D011618:Psychotic Disorders / Q000150:complications / Q000378:metabolism / Q000473:pathology; D066127:White Matter / Q000378:metabolism / Q000473:pathology*
chemical_list: D001224:Aspartic Acid; C000179:N-acetylaspartate