Unraveling Specific Brain Microstructural Damage in Moyamoya Disease Using Diffusion Magnetic Resonance Imaging and Positron Emission Tomography

Abstract Background and Purpose Chronic ischemia may induce brain microstructural damage and lead to neurocognitive dysfunction in patients with Moyamoya disease (MMD). We applied neurite orientation dispersion and density imaging (NODDI) and 15 O-gas positron emission tomography (PET) to elucidate the specific ischemic brain microstructural damage of MMD in the cortex and the white matter. Materials and Methods Thirty-one patients (16-63years old, 9 males) and 20 age- and sex-matched normal controls were enrolled in this study. NODDI evaluates quantitative parameters reflecting neurite and axonal density, network complexity and the interstitial fluid in all participants. Of 31 patients, 12 newly diagnosed patients were evaluated with PET, also. We evaluated correlations between the microstructural parameters of NODDI and the hemodynamic and metabolic parameters of PET, the relationship between NODDI and clinical severity of each hemisphere (Normal, Asymtpomatic, Symptomatic, and Infarcted) as well as neurocognitive performance. Results All NODDI parameters significantly correlated with PET parameters (absolute r  = 0.46-0.83, P ≤ .048) and clinical severity ( P r  = 0.36-0.64, P ≤ .048), but the interstitial fluid component did not. Conclusions Chronic ischemia in patients with MMD may induce decreased neurite and axonal density, simplified network complexity, and may lead to neurocognitive dysfunction. The increased interstitial fluid accompanying hemodynamic impairment may not be identical to the decreased neurite density and might be driven by another mechanism.