Novel Use of Time-Resolved Magnetic Resonance Angiography to Evaluate Retrograde Lumbar Vein Flow and Epidural Venous Plexus Enhancement in Chronic Headache Patients With and Without Nutcracker Physiology

Compression of the left renal vein by the superior mesenteric artery, known as nutcracker phenomenon (NCP), can cause retrograde flow and congestion in communicating venous systems. It has recently been speculated that NCP can result in retrograde flow and congestion of the lumbar veins and epidural venous plexus (EVP), thereby affecting the central nervous system. This study describes the novel use of time-resolved magnetic resonance angiography (trMRA) to evaluate for retrograde left second lumbar vein (L2LV) flow and early EVP enhancement in patients with chronic daily headache (CDH) with and without NCP.A retrospective analysis was performed of 31 patients with CDH (27 females and 4 males; median age, 38 years [range, 18-63 years]) who underwent trMRA centered over the L2LV to evaluate the direction of blood flow and presence of early EVP enhancement from May 2020 to March 2022. Descriptive statistics were performed, and anatomic associations were analyzed in patients with and without retrograde L2LV flow and early EVP enhancement. The accuracy of magnetic resonance imaging findings in detecting these flow patterns was also assessed.Patients with NCP who demonstrated narrowing of the left renal vein, a positive beak sign ( P = 0.052), decreased aortomesenteric distance ( P = 0.038), and decreased SMA angle demonstrated increased rates of retrograde L2LV flow and early EVP enhancement. A positive beak sign was 83% specific, and an aortomesenteric distance of ≤6.5 mm was 61% sensitive and 83% specific for identifying retrograde L2LV flow with early regional EVP enhancement in patients with CDH.Retrograde L2LV flow with early EVP enhancement in CDH patients can be effectively evaluated using trMRA and was seen with greater propensity in those patients with NCP.