Proposed Pathogenesis for a Subgroup of Patients with Neurogenic Thoracic Outlet Syndrome

Abstract

Most patients with Neurogenic Thoracic Outlet Syndrome (TOS) have upper extremity pain and paresthesia with normal neurologic examination and objective tests. The purpose of this study was to determine the pathologic nature of the resected first ribs in a subgroup of patients TOS who experienced resolution of symptoms postoperatively. Methods: In a retrospective study, we compared normal human cadaver first ribs (control, C) with first ribs from patients with proven NTOS (N). Ribs were examined for anatomic features. Preoperative and postoperative dynamic Magnetic Resonance Angiograms (MRA) of the affected and contralateral upper extremities were examined. Results: There were 41 first ribs from patients with DNTOS and 12 normal first ribs from human cadavers. In all patients (100%) with DNTOS there was a bony tubercle which corresponded to the area of subclavian vein groove in the normal ribs. Conclusion: A bony tubercle at the site of the subclavian vein groove in patients with DNTOS may be the pathologic entity which causes extrinsic compression of the subclavian vein at rest. The neurologic symptoms resolve following disarticulation and resection of the medial aspect of the first rib. In a subgroup of patients, NTOS may be the manifestation of venous ischemia of the nerves of the upper extremity as opposed to nerve compression. Type of Research: Single-center retrospective cohort study. Key Findings: A bony tubercle at the site of the subclavian vein groove in a subgroup of patients affected with DNTOS is the pathologic entity which causes extrinsic compression of the subclavian vein at rest. In these patients the neurologic symptoms resolve following disarticulation and resection of the medial aspect of the first rib. Take Home Message: A subgroup of patients with Disputed Neurogenic Thoracic Outlet Syndrome may have neurologic symptoms caused by venous ischemia of the upper extremity which is caused by extrinsic compression of the subclavian vein by a bony tubercle on the first rib at the costo-sternal joint. Table of Content Summary: This retrospective study compared normal human cadaver first ribs with first ribs from patients with proven NTOS (N). Proof of NTOS was symptom resolution following resection of the medial aspect of the first rib. The study suggests that in a subgroup of patients with Disputed Neurogenic Thoracic Outlet Syndrome, neurologic symptoms caused by venous ischemia of the upper extremity which is caused by extrinsic compression of the subclavian vein by a bony tubercle on the first rib at the costo-sternal joint