title: White matter diffusivity predicts memory in patients with subjective and mild cognitive impairment and normal CSF total tau levels.
abstract: Subjective and mild cognitive impairment (SCI and MCI) are etiologically heterogeneous conditions. This poses problems for assessment of pathophysiological mechanisms and risk of conversion to dementia. Neuropsychological, imaging, and cerebrospinal fluid (CSF) findings serve to distinguish Alzheimer's disease (AD) and other etiological subgroups. Tau-molecules stabilize axonal microtubuli; high CSF total tau (T-tau) reflects ongoing axonal damage consistent with AD. Here, we stratify patients by CSF T-tau pathology to determine if memory network diffusion tensor imaging (DTI) predicts memory performance in the absence of elevated T-tau. We analyzed neuropsychological test results, hippocampus volume (HcV) and white matter diffusivity in 45 patients (35 with normal T-tau). The T-tau pathology group showed more hippocampus atrophy and memory impairment than the normal T-tau group. In the T-tau normal group: (1) memory was related with white matter diffusivity [fractional anisotropy (FA) and radial diffusivity (DR)], and (2) FA of the genu corpus callosum was a unique predictor of variance for verbal learning, and HcV did not contribute to this prediction. The smaller sample size in the T-tau pathology group precludes firm conclusions. In the normal T-tau group, white matter tract and memory changes may be associated with normal aging, or with non-tau related pathological mechanisms.
authors.affiliation: Department of Neurology, Akershus University Hospital, Lørenskog, Norway. ramuneg@psykologi.uio.no
authors.forename: Ramune
authors.initials: R
authors.lastname: Grambaite
authors.forename: Vidar
authors.initials: V
authors.lastname: Stenset
authors.forename: Ivar
authors.initials: I
authors.lastname: Reinvang
authors.forename: Kristine B
authors.initials: KB
authors.lastname: Walhovd
authors.forename: Anders M
authors.initials: AM
authors.lastname: Fjell
authors.forename: Tormod
authors.initials: T
authors.lastname: Fladby
mesh_terms: D000328:Adult; D000368:Aged; D016880:Anisotropy; D001931:Brain Mapping; D003072:Cognition Disorders / Q000134:cerebrospinal fluid / Q000150:complications / Q000473:pathology; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods; D005260:Female; D006624:Hippocampus / Q000473:pathology; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008297:Male; D008569:Memory Disorders / Q000134:cerebrospinal fluid / Q000209:etiology* / Q000473:pathology; D008875:Middle Aged; D009413:Nerve Fibers, Myelinated / Q000473:pathology*; D009483:Neuropsychological Tests; D012044:Regression Analysis; D014706:Verbal Learning / Q000502:physiology; D016875:tau Proteins / Q000134:cerebrospinal fluid*
chemical_list: D016875:tau Proteins