Relationships Between Lateral Ventricle Size, Cerebrospinal Fluid Dynamics, and Aqueductal Resistance in Young Healthy Adults.

Background: Ventricular enlargement and abnormal cerebrospinal fluid (CSF) circulation are closely associated in communicating hydrocephalus (NPH), yet their causal relationship remains unclear. Studying healthy populations may help clarify these mechanisms. Existing metrics for CSF dynamics and ventricular morphology are limited by physiological variability such as heart rate and brain size, and aqueductal resistance has been little studied in healthy cohorts.

Purpose: To quantify aqueductal resistance and two ratio-based indices-the CSF stroke volume ratio of the aqueduct to the cervical region (Ratio-SV) and the lateral ventricle to total brain area ratio (Ratio-Area)-in a healthy population, and to examine their interrelationships.

Study type: Prospective.

Population: 34 healthy young adults (17 female, 17 male; age, 25.2 ± 3.9 years old); 4 NPH patients (2 female, 2 male; age, 50-80 years old).

Field strength/sequence: 3 T MRI with transverse 3D T1-weighted gradient echo, sagittal 3D Balanced Fast Field Echo (BFFE; gradient echo), and 2D CINE Phase Contrast (CINE-PC; gradient echo) sequences.

Assessment: Aqueductal resistance was measured on BFFE, Ratio-Area on T1-weighted images, and Ratio-SV on CINE-PC. Sex differences were also examined.

Statistical tests: Wilcoxon test was used for group comparisons, and Spearman's correlation for associations among parameters, with p < 0.05 considered significant.

Results: In healthy adults, mean aqueductal resistance was 72 ± 42 mPa s/mm³, Ratio-SV 6.0% ± 2.3% and Ratio-Area 4.5% ± 1.6%. Males exhibited a significantly lower Ratio-Area compared to females (3.9% ± 1.3% vs. 5.2% ± 1.7%). Ratio-SV was unaffected by the cardiac cycle. Aqueductal resistance showed a strong negative correlation with Ratio-SV (r = -0.65) but showed no significant correlation with Ratio-Area (r = -0.27). Ratio-SV and Ratio-Area were also uncorrelated (r = 0.08).

Data conclusion: Ratio-based metrics provide useful parameters for evaluating both ventricular morphology and CSF dynamics by reducing the influence of physiological variations. Combined with aqueductal resistance, these baseline data in healthy adults may contribute to a better understanding of the pathophysiology of NPH.

Evidence level: 2.

Technical efficacy: Stage 1.