Cervical Rib (Thoracic Outlet Syndrome)

Definition

  • Congenital anomaly where-by an extra cervical rib or posteriorly fixed brachial plexus results in ↑ angulation of the subclavian artery & first thoracic nerve over the first rib

Aetiology

  • Cervical rib from elongation of the C7 costal element
  • Incomplete ribs often continue as a fibrous band to the first rib
  • Other bony causes include anomalous first rib, long C7 transverse process and clavicle malunion
  • Soft tissue causes include scalene hypertrophy and congenital fibromuscular bands
  • Neck trauma and repetitive overhead activity
  • Drooping shoulder posture

Epidemiology

  • Cervical ribs occur in 0.4% of the population (70% are bilateral)
  • Only symptomatic in 10% of cases

Anatomy

  • Three sites of compression, interscalene triangle, costoclavicular space and subcoracoid space
  • Interscalene triangle bounded by anterior scalene, middle scalene and first rib
  • Brachial plexus and subclavian artery pass through the interscalene triangle
  • Subclavian vein passes anterior to anterior scalene
  • Lower trunk (C8 T1) lies on the first rib and is most often compressed

Pathology

  • Neurogenic thoracic outlet syndrome accounts for over 90% of cases
  • Lower trunk compression causes thenar wasting and ulnar sided sensory loss
  • Arterial compression causes subclavian stenosis, post stenotic aneurysm, thrombosis and distal emboli
  • Arterial cases nearly always have a bony anomaly
  • Venous compression causes effort thrombosis (Paget Schroetter syndrome)

Classification

TypeDescription
True neurogenicObjective neurological deficit
Disputed neurogenicSymptoms and no objective findings
Arterial
Venous

History

  • Pain and paraesthesia in the ulnar hand and medial forearm
  • Symptoms worse with overhead activity or carrying loads
  • Hand weakness and clumsiness
  • Coldness, pallor and arm claudication suggest arterial involvement
  • Swelling, cyanosis and heaviness suggest venous involvement
  • Occupation and previous neck or shoulder trauma

Examination

  • Supraclavicular fullness, tenderness or palpable cervical rib
  • Wasting of thenar, hypothenar and interossei muscles
  • Sensory loss in C8 and T1 dermatomes
  • Adson, Wright hyperabduction and Roos elevated arm stress tests
  • Compare blood pressure in both arms and listen for a subclavian bruit
  • Exclude cervical radiculopathy and ulnar nerve entrapment

Investigations

Cervical Rib (Thoracic Outlet Syndrome), chest radiograph showing a cervical rib
Chest radiograph showing a cervical rib. Image by No machine-readable author provided. KanuUli assumed (based on copyright claims)., Wikimedia Commons, Public domain.

X-rays

  • An occasional well formed rib is seen
    • yet these are less likely to cause significant symptoms
  • Elongation of the lateral mass of C7
    • likely presence of a fibrous band
    • this sharp fibrous band is more likely to result in symptoms

EMG

  • not as good as clinical examination in establishing the diagnosis

Differential Diagnosis

  • Carpal tunnel syndrome
    • but the sensory & motor changes are not confined to the distribution of the median nerve
  • Ulnar tunnel syndrome
    • again the changes are not confined to the distribution of the ulna nerve
  • Pancoast syndrome
    • (apical carcinoma of the bronchus) may infiltrate the structures at the root of the neck causing pain numbness & weakness of the hand
    • Clinically, large lump in the neck & chest X-Ray typical features of malignancy
  • Cervical spine lesions
    • TB & mets- X-Rays usually differentiate the cause
  • Spinal cord lesions
    • such as syringomyelia
    • may cause wasting of the hand but other neurological features suggest diagnosis (dissociated pain & temperature loss)
  • Cuff lesions
    • have painful shoulder & arm movements

Treatment

  • Nonoperative
    • exercises to improve support of shoulder girdle associated with weight reduction are usually adequate
  • Operative
    • excision of the rib or fibrous band
      • indicated if the above fails in the presence of severe symptoms
      • significant neurological or vascular disturbances then

Complications

  • Brachial plexus injury
  • Long thoracic and phrenic nerve injury
  • Pneumothorax
  • Subclavian artery or vein injury
  • Thoracic duct injury with chyle leak on the left
  • Recurrence from scarring or incomplete resection

Prognosis

  • Many neurogenic cases improve with physiotherapy and activity modification
  • Surgical decompression relieves pain and paraesthesia in most patients
  • Established muscle wasting seldom recovers
  • Vascular cases do well with early decompression
  • Disputed neurogenic cases have less predictable surgical outcomes

Reviewed by Professor Phong Tran, Head of Orthopaedic Surgery, Western Health. Last updated 10 October 2026.