Fluoroscopic sniff test as a diagnostic tool for phrenic nerve injury in patients with traumatic brachial plexus injury

OBJECTIVE Traumatic brachial plexus injury (BPI) is a high-morbidity condition with an escalating incidence. One of the treatment options is neurotization using the ipsilateral phrenic nerve. Therefore, diagnosis of nerve dysfunction is a crucial step in preoperative planning. This study aimed to assess the accuracy and reliability of the fluoroscopic sniff test for preoperative diagnosis of phrenic nerve injury in patients with traumatic BPI. METHODS The study was conducted from June 2019 to August 2023 at a tertiary care hospital. A preoperative fluoroscopic sniff test was performed. During brachial plexus surgery, direct phrenic nerve stimulation was conducted as a gold standard of phrenic nerve function. Two nonoperating orthopedic surgeons interpreted the accuracy and reliability of the test. RESULTS Seventy-four patients with traumatic BPI (66 males and 8 females) with a median age of 26 years were enrolled. Sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of the fluoroscopic sniff test were 90.9% (95% CI 75.7%-98.1%), 100% (95% CI 91.4%-100%), 100% (95% CI 88.4%-100%), 93.2% (95% CI 82.3%-97.6%), and 95.9% (95% CI 88.6%-99.2%), respectively. Interobserver reliability showed excellent agreement (kappa = 1, p < 0.001). CONCLUSIONS The fluoroscopic sniff test was proven to be an accurate, reliable, and simple tool to evaluate phrenic nerve function in patients with traumatic BPI. Preoperative testing should be performed to reduce operative time to identify the phrenic nerve as a donor for nerve transfer surgery in cases in which no function is detected from the fluoroscopic sniff test.