"Y sign" as an anatomical finding associated with severe hypotension in the prone position: illustrative cases

Patients with pectus excavatum occasionally develop hypotension after prone positioning during scoliosis surgery, which may result in cancellation of the surgery. The imaging characteristics associated with severe hypotension in patients with pectus excavatum remain unclear. The authors compared the cases of 3 scoliosis patients with pectus excavatum who developed hypotension after prone positioning, focusing on the spatial relationship between the great vessels and the thoracic cage on CT.

In only 1 of the 3 patients was the hypotension refractory to fluids and vasopressors. CT scans showed that the inferior vena cava (IVC) was located directly anterior to the aorta, and the great vessels were situated in the narrow space between the costal cartilage and the vertebral body; in the prone position, they might be easily crushed by the anterior chest wall. The chest wall, the great vessels, and the vertebral body formed a distinctive Y-shaped configuration, which the authors designated as the "Y sign."

Hypotension after prone positioning in scoliosis patients with pectus excavatum is presumed to result from compression of the right heart and the IVC. The Y sign may represent an anatomical risk factor for refractory hypotension in the prone position and may support consideration of pectus excavatum repair before scoliosis surgery. https://thejns.org/doi/10.3171/CASE26246.