Cerebral structure and function changes in adult neuronal intranuclear inclusion disease: a study of 16 patients.

Neuronal intranuclear inclusion disease (NIID) is a rare neurodegenerative disorder characterized by significant clinical heterogeneity. This study aimed to characterize the structural and functional neural correlates underlying its symptomatology using multimodal neuroimaging. Sixteen patients with NIID and matched controls underwent clinical, cognitive, and multimodal neuroimaging assessments. Diffusion tensor imaging (DTI) and functional near-infrared spectroscopy (fNIRS) were acquired to evaluate white matter microstructure and resting-state cortical connectivity, respectively, which were then correlated with clinical metrics. The common manifestations of patients with NIID were dementia (56.3%), tremors (50.0%), headache (31.3%), sensory disturbance (31.3%), and paroxysmal symptoms (25.0%). Patients with NIID exhibited significantly reduced brain connectivity compared to controls, including the left prefrontal cortex (PFC) - right PFC, left-right motor cortex, and left PFC - left motor cortex connections (false discovery rate-corrected p < 0.05). Additionally, DTI analysis revealed significantly altered white matter regions and fibers in patients with NIID. MoCA scores had a significantly positive correlation with fractional anisotropy in the left anterior corona radiata (ACR) but a negative correlation with axial diffusivity in the bilateral ACR. Additionally, exploratory analyses suggested that cognitive impairment was potentially associated with injury to the superior longitudinal fasciculus (SLF), and tremor may be related to the external capsule, tapetum, corticospinal tract, fornix, and SLF. Patients with NIID exhibited distinct patterns of disrupted white matter integrity and functional cortical connectivity that underlie core clinical features like dementia and tremor. The combined DTI-fNIRS approach offers novel insights into NIID pathophysiology and identifies potential neuroimaging biomarkers for diagnosis and monitoring.