False positive perfusion lung scintiscans in tetraplegic patients: a case series

An accurate diagnosis of pulmonary embolism is essential to prevent excessive morbidity and mortality from either inappropriate therapy or failure to institute anticoagulation. The diagnosis of pulmonary embolism in tetraplegic spinal cord injury patients is complicated by frequent inability to perform the ventilation portion of the ventilation-perfusion scintiscan (V/Q scan) and by controversy regarding classification of defects on perfusion-only scans, as well as by coexisting pulmonary disease, systemic illness, related injuries, and the tendency for tetraplegic patients to have unexplained fever. This report describes three tetraplegic ventilator-dependent patients with hypoxic respiratory failure and normal chest radiographs who had large defects on perfusion-only lung scans. Ventilation scintiscans were not performed because the patients were ventilator-dependent with tracheostomies. Pulmonary angiography findings were normal in all patients, and all three responded to aggressive pulmonary toilet. Even large defects on perfusion-only scans despite normal chest radiographs should not be used to establish a diagnosis of pulmonary embolism in tetraplegic patients, and further diagnostic imaging is warranted.