Retrograde lumbar vein flow and epidural venous congestion in chronic headache patients with or without nutcracker...

Narrowing of the left renal vein (LRV) between the superior mesenteric artery (SMA) and the aorta, known as Nutcracker phenomenon (NCP), can obstruct venous outflow, rerouting blood through collateral pathways such as the left second lumbar vein (L2LV) and congesting the epidural venous plexus (EVP). This may disrupt the venous-CSF pressure balance, contributing to chronic headaches. The use of time-resolved magnetic resonance angiography (trMRA) for this evaluation has been previously studied, and this expanded database aims to assess the anatomical findings predicting retrograde L2LV flow and EVP congestion in chronic headache patients, using a larger cohort.

A total of 98 CDH patients (10.2 % male, 89.8 % female) with a mean age of 40 ± 16 years and BMI of 24.4 kg/m² were referred for trMRA between May 2020 and November 2024. Imaging was performed with trMRA focused on the L2LV to assess blood flow directionality and early regional EVP congestion. Descriptive statistics and anatomical correlations with retrograde L2LV flow and EVP congestion were analyzed. Receiver operator Characteristics (ROC) analysis was also performed to measure the accuracy of the MRI findings in predicting L2LV flow and EVP congestion.

Retrograde L2LV flow and EVP congestion were observed in 39.8 % of patients. Compared to the negative group, the positive group had significantly smaller aortomesenteric distance (AMD) (5.48 ± 3.05  mm vs. 10.75 ± 4.04  mm; p < 0.001), narrower SMA-aortic angle (28.55 ± 15.91° vs. 50.83 ± 28.43°; p < 0.001), larger L2LV size (3.7 ± 0.89  mm vs. 2.6 ± 0.88  mm; p < 0.001), narrower left renal ptosis angle (37.4 ± 17.3° vs. 52.5 ± 18.4°; p = 0.001), greater percentage change in LRV diameter (85.95 ± 11.20 % vs. 75.04 ± 14.96 %; p < 0.001) and more frequent beak sign (p < 0.001). Logistic regression identified aortomesenteric distance (OR: 1.31; 95 % CI: 1.03-1.67; p = 0.031), beak sign (OR: 4.07; 95 % CI: 1.05-15.73; p = 0.043), L2LV size (OR: 2.66; 95 % CI: 1.56-4.54; p < 0.001), and left renal ptosis angle (OR: 1.51; 95 % CI: 1.09-2.10; p = 0.013) as independent predictors. ROC analysis showed that AMD at ≤ 7.5  mm had AUC 0.878, sensitivity 87.2 %, specificity 79.7 %, PPV 73.9 %, NPV 90.4; L2LV size at ≥ 2.7  mm had AUC 0.81, sensitivity 89.7 %, specificity 67.8 %, PPV 80.0 %, NPV 72.5; left renal ptosis angle at ≥ 45.9° had AUC 0.80, sensitivity 76.3 %, specificity 76.9 %, PPV 63.2 %, NPV 79.3, and beak sign presence had AUC 0.706, sensitivity 66.7 %, specificity 74.6 %; PPV 63.4 %, NPV 77.2. Combining these predictors with the beak sign further improved their performance metrics.

This expanded cohort confirms and strengthens prior findings that specific anatomical parameters, including AMD, L2LV size, left renal ptosis angle, and the beak sign, are significantly associated with retrograde L2LV flow and EVP congestion in chronic headache patients with NCP. These findings may help in predicting which patients are likely to have retrograde L2LV flow and EVP congestion.