White matter structural integrity and transcranial Doppler blood flow pulsatility in normal aging

Area of Science:

• Neuroimaging
• Vascular Neurology
• Gerontology

Background:

• Cerebrovascular diseases are a major cause of age-related cognitive impairment.
• White matter (WM) integrity is crucial for cognitive function and is often affected by small vessel disease.
• The precise mechanisms linking vascular health to WM microstructural changes remain under investigation.

Purpose of the Study:

• To investigate the association between arterial pulsatility and white matter structural integrity in older adults.
• To determine if this association is artery-specific and regional.
• To explore the underlying mechanisms of vascular-related white matter injury.

Main Methods:

• Voxel-wise analysis of MRI images in adults over 70 years old, free of stroke and dementia.
• Measurement of fractional anisotropy (FA) using diffusion tensor imaging to assess WM integrity.
• Measurement of pulsatility index (PI) using transcranial Doppler ultrasound to assess arterial pulsatility.

Main Results:

• Significant correlations were found between elevated PI and reduced FA in specific WM regions.
• These associations were artery-specific and regional, extending beyond the assessed vascular territories.
• The findings support a vascular hypothesis of WM injury, independent of aging effects alone.

Conclusions:

• Elevated arterial pulsatility is associated with white matter microstructural damage in older adults.
• The injury mechanism may involve mechanical forces from pulsating vessel walls rather than solely perfusion.
• These findings highlight the impact of vascular pulsatility on brain health and cognitive aging.