Resting pulsatile cerebrovascular hemodynamics in people with Down syndrome.

Individuals with Down syndrome (DS) exhibit reduced resting cerebral blood flow (CBF) and altered arterial pulsatility. Pulsatility and its transmission from extracranial [internal carotid (ICA), vertebral (VA)] to intracranial [middle (MCA), posterior (PCA)] arteries is characterized utilizing the damping factor index (DFi), with values > 1 suggesting attenuation of pulsatility, and < 1 indicating harmful transmission. To our knowledge, resting cerebral arterial pulsatility in individuals with DS has not been assessed. Therefore, the present study investigated resting attenuation of arterial pulsatility, quantified using the DFi, and CBF in individuals with DS (DS; n = 16, 5 females) and age- and sex-matched controls (n = 16, 5 females). Participants were instrumented in a semi-recumbent position for 10 minutes. During this period, heart rate, blood pressure, end-tidal oxygen and carbon dioxide, and MCA and PCA velocities were continuously measured. Following this, one-minute ICA and VA blood flow measures were performed via vascular duplex ultrasound. Anterior DFi was not different between individuals with DS (1.76 ± 0.55 a.u.) vs. controls (1.93 ± 0.66 a.u.; p = 0.453). Posterior DFi was greater in DS (3.17 ± 0.70 a.u.) vs. controls (2.30 ± 0.59 a.u.; p = 0.001). These data suggest that individuals with DS can attenuate arterial pulsatility under resting conditions.