(VP020) CEREBRAL WHITE MATTER LESIONS AND ITS ASSOCIATIONS WITH BRAIN PULSATILITY: AN MRI, NIRS, AND TCD STUDY

Background: Age-related elevated cerebral pulsatility is thought to damage cerebral microcirculation and impose modifications on the brain structure. White matter lesions (WMLs) are often found in older adults and are indicative of cerebral small vessel diseases. Although vascular dysfunction is considered a common cause of both conditions, the relationship between cerebral pulsatility and WMLs remains unclear. We examined the association between indices of cerebral pulsatility and the volume of WMLs in seniors.

METHODS AND RESULTS: 22 older adults, 60 – 79 years, 68.812 ± 5.35, 86.36% female underwent a series of multimodal brain imaging data collection. Structural magnetic resonance imaging (MRI, Siemens 3T) scans consisted of a T1-weighted image (MP-RAGE, TR/TE = 2300/2.32 ms, resolution: 0.9x0.9x0.9 mm3), and a flow-attenuated inversion recovery (FLAIR) image (3D, TR/TE = 5000/3.88 ms, resolution: 1x1x1 mm3, sagittal orientation). These images were used as inputs of segmentation pipeline of FreeSurfer software to calculate white matter hypointensities (WM‐hypo) volume normalized to estimated total intracranial volume. Near-infrared spectroscopy (NIRS) was used to acquire hemodynamics data at rest (fs = 25 Hz, 11 sources, 9 detectors, 756 nm and 853 nm, 46 channels) with the source-detector arrangement covering the prefrontal cortex. The NIRS intensity data were normalized to their temporal means and bandpass filtered with cutoff frequencies of 0.5 – 5 Hz to preserve cardiac components. The pulsatile component of NIRS data was then used to extract the cerebral pulse amplitude (CPA) by subtracting systolic peak from diastolic peak divided by systolic peak. Transcranial Doppler (TCD) was used to acquire blood velocity in the right middle cerebral artery (MCA) for 5 min. The cerebral arterial pulsatility (CAP) in MCA was derived from the differential velocity between systole and diastole, divided by the mean flow velocity. The data was controlled for sex. Correlation analysis was used to explore the association between cerebral pulsatility and WM-hypo volume.
Data indicated that there is a statistically significant positive association between WM-hypo volume and cerebral arterial pulsatility measured with TCD (r= 0.4308, p= 0.0453). Also, WM-hypo volume had a marginally significant positive association with cerebral microcirculation pulsatility indexed with NIRS (r= 0.4210, p= 0.0511).

Conclusion: Higher cerebral arterial pulsatility, measured using transcranial Doppler (TCD) as a marker of arterial stiffness, is significantly associated with a higher volume of white matter lesions (WMLs) in older adults. However, when measuring pulsatility using near-infrared spectroscopy (NIRS) in the prefrontal cortex, the association between pulsatility and WML volume only showed a trend.