Vertebral Mass Mimicking Thoracic Outlet Syndrome: A Case Report with Literature Review

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Abstract Introduction: Neurogenic thoracic outlet syndrome is the most common subtype of thoracic outlet syndrome and can be readily mimicked and misdiagnosed. This report presents a rare cervical vertebral lesion mimicking neurogenic thoracic outlet syndrome, highlighting an important diagnostic pitfall. Case presentation: Presenting with two years of left shoulder pain and immobility following heavy labor, a 17-year-old male underwent provocative testing and nerve conduction studies suggesting left neurogenic thoracic outlet syndrome. Despite improvement with physiotherapy, imaging revealed an expansile lytic mass at the C7 level, measuring 55 × 36 × 32 mm. Biopsy favored chondromyxoid fibroma. Surgical excision was decided, and the patient was lost to follow-up. Literature review: Five cases of cervicothoracic lesions presenting as thoracic outlet syndrome were reviewed, three of which were female. Pain and paresthesia were the most common symptoms, and the neurogenic subtype predominated. Most lesions arose from the first rib, and histology varied, including aneurysmal bone cyst, osteoblastoma, chondrosarcoma, and hydatid cyst. All patients underwent surgical excision, with symptom resolution or improvement. Conclusion: Cervical vertebral lesions can mimic neurogenic thoracic outlet syndrome, highlighting the importance of imaging in identifying underlying structural pathology. Introduction Thoracic outlet syndrome (TOS), first described by Peet et al. in 1956 [1], is characterized by compression of the neurovascular structures as they pass through the thoracic outlet between the lower neck and the axilla. It is broadly classified into two forms: vascular TOS, resulting from compression of the subclavian artery or vein, and neurogenic TOS (nTOS), which arises from compression of the brachial plexus. The nTOS subtype is by far the most common, accounting for more than 90% of cases, whereas venous TOS represents approximately 5% and arterial TOS is the least frequent, comprising about 1% of cases [2]. As no single investigation is confirmatory for the neurogenic form, diagnosis relies heavily on clinical assessment and is generally considered one of exclusion [3,4]. Since it can overlap with conditions such as cervical radiculopathy, entrapment neuropathies like carpal tunnel syndrome, and various musculoskeletal disorders, including rotator cuff pathology, it is readily mimicked and frequently misdiagnosed [2]. Less commonly, the syndrome can arise from discrete structural or space-occupying lesions of the cervicothoracic region, including tumors, cysts, anomalous muscles, or post-surgical hardware, which may lie away from the outlet itself and are therefore prone to being overlooked without careful anatomical localization [5]. Imaging therefore plays an important role, both in excluding the conditions that mimic the syndrome and in occasionally revealing an underlying tumor or structural lesion responsible for the symptoms [6]. Chondromyxoid fibroma is a rare benign primary bone tumor, accounting for under 0.5% of all primary bone neoplasms, that most often arises in the metaphysis of the long bones of the lower limb, typically the proximal tibia, and is only exceptionally found in the cervical spine, where it may present with neck pain and upper-limb numbness and paresthesia [7]. Reports of cervical vertebral lesions presenting with the clinical and electrodiagnostic features of nTOS are scarce. Therefore, this case highlights a potential diagnostic pitfall. This report was prepared in accordance with the CaReL guidelines, and all references were verified for eligibility [8,9]. Case Presentation Patient Information A 17-year-old male presented with a two-year history of intermittent left shoulder pain that gradually increased in severity, followed by the recent onset of shoulder immobility. The symptoms initially began following heavy physical work. His past medical and surgical history was unremarkable. Clinical Findings On physical examination, the patient was hemodynamically stable with normal vital signs, and distal pulses were intact. Provocative testing was positive for nTOS, with reproduction of symptoms on the Elvey test (upper-limb tension test) and the EAST (elevated arm stress test). There was marked tenderness over the scalene muscles, which had a firm, “stony” consistency on palpation. No radicular symptoms or additional neurological deficits were identified. Diagnostic Approach Nerve conduction studies were within normal limits apart from a reduced sensory amplitude of the left medial antebrachial cutaneous nerve compared with the right (13.0 µV versus 18.1 µV; a 28.2% side-to-side difference), suggesting mild left-sided nTOS (Table 1). Carpal tunnel syndrome, cervical radiculopathy, accessory nerve lesion and suprascapular neuropathy were excluded. Chest radiography showed no significant abnormality. As the clinical picture was consistent with TOS, the patient was started on a one-month course of TOS-specific physiotherapy, with follow-up planned thereafter. At one-month follow-up, the patient showed a marked response to physiotherapy: all provocative tests were relieved, scalene muscle tenderness had resolved, and the elevated arm stress test was negative, with only a mildly positive Elvey test on the affected side. A Doppler ultrasound performed for follow-up at this visit demonstrated a 40 × 15 × 10 mm heterogeneously hypoechoic left paraspinal lesion, suggesting compression of the adjacent nerve roots. For further characterization, magnetic resonance imaging (MRI) was obtained and revealed a well-circumscribed, expansile lytic mass at the C7 level measuring 55 × 36 × 32 mm (Figure 1). Therapeutic Intervention The patient was referred to the neurosurgery department for further work-up. A computed tomography (CT)-guided biopsy was scheduled, and biopsies were obtained from the left transverse process of the C7 vertebra using an 18-gauge coaxial needle. The procedure was uneventful, with no significant complications, and following it, the patient was able to move the left upper limb and hand without obvious limitation. Histopathological examination of the core biopsy showed blood-filled cystic spaces lined by fibrous septa, hypocellular myxoid foci with bland spindle cells, and fibroblastic areas containing unevenly distributed osteoclast-type giant cells, with no necrosis. Patchy strong cytoplasmic S100 staining supported chondroid differentiation. The lesion was reported as a giant cell-rich lesion with secondary aneurysmal bone cyst change, favoring chondromyxoid fibroma, with giant cell tumor of bone remaining in the differential (Figure 2). Follow-up Following multidisciplinary team discussion, surgical excision was recommended as definitive management because of the lesion’s location and potential for further enlargement, which could make subsequent excision more difficult, as well as the need for definitive histopathological diagnosis. However, the patient declined the proposed procedure and was subsequently lost to follow-up. Table 1. Nerve conduction studies: antidromic sensory summary Peak (ms) Normal Peak (ms) P-T Amp (µV) Normal P-T Amp (µV) Site 1 Site 2 Delta-P (ms) Dist (cm) Vel (m/s) Left Medial Antebrachial Cutaneous Antidromic Sensory (Medial Forearm) 2.0 — 13.0 — Elbow Medial Forearm 2.0 0.0 — Right Medial Antebrachial Cutaneous Antidromic Sensory (Medial Forearm) 2.2 — 18.1 — Elbow Medial Forearm 2.2 0.0 — Left Median Antidromic Sensory (2nd Digit) 2.9 <3.5 150.6 >20 Wrist 2nd Digit 2.9 13.0 45 Left Ulnar Antidromic Sensory (5th Digit) 2.5 <3.1 94.2 >17.0 Wrist 5th Digit 2.5 11.0 44 Right Ulnar Antidromic Sensory (5th Digit) 2.9 <3.1 77.5 >17.0 Wrist 5th Digit 2.9 11.0 38 Abbreviations. P-T Amp, peak-to-peak amplitude; Delta-P, peak latency difference; Dist, distance; Vel, conduction velocity; ms, millisecond; µV, microvolt; cm, centimeter, m/s, meter per second Discussion Neurogenic TOS is the most difficul

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