Congenital first and second rib fusion causing neurogenic thoracic outlet syndrome in an adolescent

Abstract

A 14-year-old girl presented with progressive right-sided neck and shoulder pain and ulnar-distribution paresthesia, consistent with neurogenic thoracic outlet syndrome. Computed tomography imaging revealed congenital fusion of the right first and second ribs causing brachial plexus compression. Conservative therapy was ineffective, and she underwent a transaxillary resection of the fused right first and second ribs with anterior scalenectomy. Intraoperatively, dense periosteal scarring and brachial plexus entrapment were identified. Symptoms fully resolved postoperatively. Congenital first-second rib synostosis is an exceptionally rare cause of pediatric neurogenic thoracic outlet syndrome. Early recognition and surgical decompression can prevent chronic disability and restore normal function.

Thoracic outlet syndrome (TOS) encompasses a spectrum of disorders resulting from compression of neurovascular structures—specifically the brachial plexus, subclavian artery, or subclavian vein—as they traverse the thoracic outlet, the anatomical space between the clavicle and first rib.¹ TOS is broadly classified into neurogenic, venous, and arterial types, with neurogenic TOS representing most cases in adults and a substantial proportion in pediatric patients.^2,3 Neurogenic TOS typically manifests as pain, numbness, and weakness in the upper extremity.^1,2,4

TOS most commonly affects young adults and is often associated with trauma, repetitive overhead activity, or anatomical anomalies such as cervical ribs.⁴ In the pediatric population, TOS is less common and more frequently associated with congenital anomalies, although congenital fusion of the first and second ribs remains exceedingly rare.^3,5,6 Notably, recent systematic reviews highlight that bony abnormalities account for a smaller proportion of pediatric TOS compared with adults.³ Furthermore, these reviews also noted that neurogenic TOS is somewhat less prevalent in children than in adults, with venous and arterial forms being relatively more common in younger patients.³ Early recognition and individualized management are critical to prevent chronic disability.^1,7

We present the case of a 14-year-old girl with life-limiting chronic neck and shoulder pain secondary to congenital fusion of the first and second ribs. This resulted in neurogenic TOS that was managed successfully with surgical decompression with a transaxillary right first and second rib resection. Informed consent was obtained from the patient and her legal guardian for publication of this case report and accompanying images.

Case report

A 14-year-old, right-handed girl, 5′3″ and 120 lb, with no significant past medical history presented with progressively worsening pain on the right side of her neck and shoulder. Her symptoms started 5 years before presentation, but symptoms were progressive and evolved into a constant, throbbing pain in her neck and shoulder that became severely debilitating for basic daily activities. She experienced intermittent numbness in the fifth digit of her right hand after prolonged arm use. She became unable to complete her schoolwork given her pain and numbness with writing and typing. Furthermore, even in the absence of repetitive motion activities and elevated arm usage, she was unable to sleep at night given the pain and throbbing in her right arm and shoulder. She has no history of trauma, intense sports or athletics, or previous surgeries involving her neck or upper limbs. She has no history of tobacco, alcohol, or recreational drugs use. Her family history was unremarkable except for her mother's type 1 diabetes.

On physical examination, she had asymmetrical shoulders with her right shoulder rounded and depressed compared with the left. A prominent pulse was noted over the right subclavian artery in the supraclavicular space. Significant tenderness was present over the right anterior scalene muscle, which was noted to be tight and hypertrophied compared with the left. The Elevated Arm Stress Test reproduced numbness along the ulnar nerve distribution on the right arm after only a few seconds; the left side was asymptomatic. Her Adson's test was negative bilaterally.

Imaging studies revealed congenital fusion of the right first and second ribs with a concave deformity at the fusion site, without evidence of a cervical rib or abnormality on the left side (Fig 1). A computed tomography angiogram of the chest was performed to evaluate the neurovascular structures, which demonstrated a clear fusion of the first and second ribs just posterior to the subclavian artery (Fig 2) without evidence of dissection or aneurysm, but accentuated tortuosity of the artery from the synostosis as compared with the left side (Fig 3). The cervical spine was also deviated laterally, likely owing to chronic mechanical strain from the rib anomaly. Given the structural deformity to her thoracic outlet and subclavian artery, this finding was suggestive of distortion and compression of the brachial plexus as well.

Fig 1.

Plain chest radiograph with arrow denoting the abnormal right first rib that fuses to the second rib. No cervical ribs present.

Fig 2.

(A) Computed tomography (CT) scan of the chest with point of fusion of the right first and second rib in coronal view. (B) CT scan of the chest demonstrating right first and second rib fusion and apical chest wall deformity in sagittal view.

Fig 3.

Computed tomography angiogram of the chest demonstrating the distortion of the right subclavian artery from first rib abnormality.

Based on her clinical presentation and imaging findings, she was diagnosed with neurogenic TOS. She initially underwent TOS-directed physical therapy of 4 months, which did not yield any relief. She additionally had adjunctive therapy including aquatic therapy and transcutaneous electrical nerve stimulation, which did not improve her symptoms. A right anterior scalene block with lidocaine was then performed by pain management without relief in symptoms. During these therapies, she had worsening paresthesia that progressed to all digits of her right hand. Given the severity of her symptoms without improvement from conservative therapy, we elected to proceed with operative decompression.

She underwent a right transaxillary resection of the fused first and second ribs along with an anterior scalenectomy (Fig 4). Intraoperatively, the first rib demonstrated significant periosteal thickening most pronounced at the point of fusion to the second rib, causing dense scarring and compression of the brachial plexus and distortion of the subclavian artery. The anterior scalene muscle was noted to insert on the second rib as opposed to the first rib. Blunt dissection with periosteal elevators and kittners was used to separate the intercostal muscles from the inferior aspect of the first and second rib. Electrocautery was used to divide the anterior scalene over a right angle. A clear plane on the first and second ribs was established allowing visualization of the subclavian vein, subclavian artery, and brachial plexus. The second rib was divided anteriorly and posteriorly with a bone cutter allowing mobilization of the fused first rib away from the artery and nerve. The first rib was then transected interior to the neurovascular structures. The residual first rib was then sequentially transected using a combination of a bone cutter and rongeur until it was clear from the brachial plexus. A limited neurolysis of the visible brachial plexus was performed sharply. Given the dense scar, a small pleural tear was created from the removal of the ribs. A 12F chest tube was placed through the pleural violation into the chest cavity and placed on suction.

Fig 4.

Fused right first and second rib after removal from a transaxillary approach.

Postoperatively, the patient's pain was well-controlled with limited use of narcotic pain medication. The chest tube was placed to water seal overnight and removed on the morning of postoperative day 1. She was discharged later that day. At the patient's 1-month follow-up, she reported complete resolution of her neck pain and neuropathic symptoms, improved sleep, and had returned fully to her normal activities without limitations. She continued physical therapy and experienced only occasional subscapular muscle spasms, which improved with heat therapy. At 1 year, she continued to have significant improvement in her arm and neck symptoms with only occasional neck pain and headaches.

Discussion

This case highlights a rare congenital cause of neurogenic TOS in a pediatric patient—fusion of the first and second ribs. TOS in pediatric patients is uncommon, and congenital fusion of the first and second ribs is an especially rare cause. Although cervical ribs are the most recognized bony anomaly associated with TOS, true synostosis between the first and second ribs has only been described in isolated case reports and is far less frequently encountered in children than other anomalies such as cervical or rudimentary ribs.^1,5 In adolescents, symptoms are often initially attributed to musculoskeletal strain or posture-related dysfunction, but persistent focal symptoms—particularly those reproducible on provocative testing—should prompt evaluation for structural causes.^4,7

Pediatric TOS also differs from adult TOS in its overall pattern of presentation. Multiple clinical series demonstrate that vascular TOS is proportionally more common in children, and neurogenic TOS, although still prevalent, accounts for a smaller share of cases relative to adults.8, 9, 10 In Rigberg et al,⁸ teenage patients most often presented with neurogenic symptoms, but congenital rib fusion was absent. Additionally, Arthur et al⁹ observed a predominance of vascular pathology, with bony abnormalities usually involving cervical ribs rather than fused ribs. More recent large-volume data from Ng et al¹⁰ reaffirm that congenital bony anomalies are present in only a minority of pediatric TOS cases, and none involved first-second rib fusion. A 2024 systematic review synthesizing 356 pediatric cases further confirmed that structural bony abnormalities are uncommon, with sports-related or repetitive motion mechanisms comprising more than one-half of presentations.¹¹ Together, these studies highlight the rarity of congenital rib synostosis and reinforce the importance of individualized evaluation in adolescents with chronic upper extremity symptoms.

The initial management of neurogenic TOS centers on physical therapy and targeted muscle interventions; however, in cases involving fixed bony compression, conservative therapy often fails.^2,4,8, 9, 10, 11, 12 Across pediatric series, surgical decompression is associated with high rates of symptomatic improvement, return to activity, and low complication rates.8, 9, 10^,12,13 Our patient's lack of improvement with conservative therapy and complete postoperative recovery align with these reported outcomes and illustrate the effectiveness of surgical decompression for congenital rib anomalies. This case contributes to the limited literature on congenital first-second rib fusion as a cause of pediatric neurogenic TOS. Early anatomical evaluation is essential, because timely surgical intervention can prevent chronic neuropathic changes and restore full function. Given the scarcity of reported cases, this patient's presentation expands the recognized spectrum of congenital etiologies in pediatric TOS and underscores the need for clinicians to consider rare bony anomalies when evaluating adolescents with persistent neck and shoulder pain.

Funding

None.

Disclosures

None.