Non-Gaussian Diffusion Imaging Shows Brain Myelin and Axonal Changes in Obstructive Sleep Apnea

Area of Science:

• Neuroimaging
• Neurology
• Medical Physics

Background:

• Obstructive sleep apnea (OSA) is linked to brain alterations affecting autonomic, cognitive, and mood regulation.
• Traditional Gaussian-based diffusion tensor imaging (DTI) has limitations in fully characterizing these brain changes.
• Non-Gaussian diffusion measures offer a more sensitive approach to assess microstructural integrity.

Purpose of the Study:

• To evaluate axonal and myelin damage in OSA patients using non-Gaussian diffusion kurtosis imaging (DKI).
• Specifically, to assess changes using axial kurtosis (AK) and radial kurtosis (RK) measures.

Main Methods:

• Diffusion kurtosis imaging data were acquired from 22 OSA patients and 26 healthy controls.
• Axial kurtosis (AK) and radial kurtosis (RK) maps were computed.
• Group comparisons were performed using analysis of covariance after normalization and smoothing.

Main Results:

• Increased AK (axonal changes) was observed in the insula, hippocampus, amygdala, pons, and cerebellar peduncles.
• Higher RK (myelin changes) was detected in the hippocampus, amygdala, temporal and frontal lobes, insula, pons, and cerebellar peduncles.
• DKI measures revealed more extensive axonal and myelin damage than previously identified with Gaussian-based methods.

Conclusions:

• Axial kurtosis and radial kurtosis (DKI) measures demonstrate widespread changes in OSA brain regions.
• These non-Gaussian measures are more sensitive to neural injury in OSA compared to traditional Gaussian-based techniques.
• DKI provides a more comprehensive assessment of microstructural damage in OSA.