Impact of aging on cerebral vasoregulation and parenchymal integrity

Sufficient vasodilatory and vasoconstrictive reactivity of cerebral arterioles is an important prerequisite for adequate capillary perfusion. To appreciate its capacity during aging and to elucidate its impact on parenchymal integrity we undertook a correlation using ultrasonography and brain MRI. Sixty healthy persons with no stenoses in the carotid and vertebral arteries were examined by transcranial Doppler to assess middle cerebral artery mean flow velocities (MFV) at rest, after 30 s apnea and after 90 s hyperventilation. Young persons, N=20, with a mean age of 24.8 (20-32) were compared with the middle aged, N=20, 54.8 (40-63) and elderly, N=20, 76.2 (69-84). A different cohort of 40 elderly persons, with a mean age of 68.4 (57-85) were evaluated also by MRI using FLAIR and T2-weighted sequences. Their extent of leukoaraiosis measured by the Fazekas scale was correlated with their vasoregulatory capacity.

The steady state MFV in young persons, 71 cm/sec, decreases to 48.1 and to 44.9 cm/sec in the middle and the old aged. The post-apnoic vasodilatation in young persons accelerates the MCA blood velocity by 41.7%, while in middle and old age only by 37.6 and 32.9% respectively. The MCA deceleration post-hyperventilation by 50.2% in young people decreases to 39.1% and to 29.7% respectively in the older categories. The correlation of periventricular hyperintensities and deep white matter lesions was found highest with the index of resistance (0.45, p<0.05) while with the apnoic acceleration and hyperventilatory deceleration it was minimal (0.01 and 0.08 respectively).

The extent of vasoregulatory capacity during aging decreases along with the decreasing basic MFV. Its effect on the initial stages of leukoaraiosis is minimal.