Phase-contrast MRI analysis of cerebral blood and CSF flow dynamic interactions

Abstract Background Following the Monro-Kellie doctrine, the Cerebral Blood Volume Changes (CBVC) should be mirrored by the Cerebrospinal Fluid Volume Changes (CSFVC) at the spinal canal. Cervical level is often chosen to estimate CBVC during the cardiac cycle. However, due to the heterogeneity in the anatomy of extracranial internal jugular veins and their high compliance, we hypothesize that the intracranial level could be a better choice to investigate blood and cerebrospinal fluid (CSF) interactions. This study aims to determine which level, intracranial or extracranial, is more suitable for measuring arterial and venous flows to study cerebral blood and CSF dynamics interactions. Methods The spinal CSF and cerebral blood flow measured at intracranial and extracranial levels were quantified using cine phase-contrast magnetic resonance imaging (PC-MRI) in 38 healthy young adults. Subsequently, CSFVC and CBVC were calculated, and by linear regression analysis (R 2 and slope), the relationship between CBVC at both levels and the spinal CSFVC was compared. The differences between extracranial and intracranial measurements were assessed using either a paired Student’s t-test or Wilcoxon’s test, depending on the normality of the data distribution. Results The CBVC amplitude was significantly higher at the extracranial level (0. 89 ± 0. 28 ml/CC) compared to the intracranial level (0. 73 ± 0. 19 ml/CC; p < 0. 001). CSF oscillations through the spinal canal do not completely balance blood volume changes. The R 2 and the slope values obtained from the linear regression analysis between CSF and blood flows were significantly higher in magnitude for the intracranial CBVC (R 2: 0. 82 ± 0. 16; slope: − 0. 74 ± 0. 19) compared to the extracranial CBVC (R 2: 0. 47 ± 0. 37; slope: -0. 36 ± 0. 33; p < 0. 001). Interestingly, extracranial CBVC showed a greater variability compared to intracranial CBVC. Conclusion Our results confirmed that CSF does not completely and instantaneously balance cerebral blood expansion during the cardiac cycle. Nevertheless, the resting volume is very small compared to the total intracranial volume. To our knowledge, this study is the first to demonstrate these findings using cerebral blood flow measured intracranially below the Circle of Willis. Additionally, our findings show that cerebral arterial and venous flow dynamic measurements during the cardiac cycle obtained by PC-MRI at the intracranial plane strongly correlate with CSF oscillations measured in the spinal canal. Therefore, the intracranial vascular plane is more relevant for analyzing cerebral blood and CSF interactions during the cardiac cycle compared to measurements taken at the cervical vascular level.