Cervical Rib
A cervical rib (CR), also called a supernumerary cervical rib, is a congenital extra rib that develops above the first rib, just superior to the clavicle. This anatomical variant results from overdevelopment of the transverse process of the cervical spine, which persists and partially or completely ossifies instead of regressing during fetal development. The condition is thought to be related to mutations in Hox genes, which regulate development of the axial skeleton in humans and other vertebrates¹.
A CR may be unilateral or bilateral and may be completely ossified, partially developed, or represented only by a fibrous band connecting the C7 transverse process to the first rib. It may also be free-floating without a bony connection or end as a nodular thickening in the neck⁵. In most cases, a cervical rib is asymptomatic and discovered incidentally on imaging². When symptoms occur, they are usually caused by compression of neurovascular structures, particularly in association with thoracic outlet syndrome (TOS), which occurs up to ten times more frequently in people with a cervical rib⁴.
Most people do not develop symptoms, but when the extra rib causes neurovascular compression it can result in significant functional impairment. In TOS, both the brachial plexus and subclavian artery may be involved. Cervical ribs are among the earliest documented anatomical variants and were described as far back as Galen and Vesalius³.
Anatomical Development and Classification
A cervical rib develops when ossification of the lateral costal element at C7 persists. Normally this structure regresses during fetal development, but when it does not, a bony structure may develop and in some cases attach anteriorly to the first rib⁶. Cervical ribs arising from C6 or C5 have also been documented⁷.
The rib has an anatomical structure consisting of a head, neck and tubercle and has no physiological function. It is commonly classified as complete or incomplete, with four further subtypes⁹:
Type 1: Only an elongated transverse process.
Type 2: The extension reaches the first rib but does not form a true joint.
Type 3: The rib is separate from the transverse process but connected to the first rib by fibrous cartilage.
Type 4: A complete cervical rib with an articulation to the lateral part of the first rib.
Prevalence and Epidemiology
Prevalence varies considerably between populations and geographic regions. Meta-analyses estimate that cervical ribs are present in approximately 1% of the healthy population¹. Among patients with TOS, up to 30% have a concurrent cervical rib. In Anatolia, Turkey, prevalence has been reported at 3%, with a higher prevalence among women⁹. Other studies report rates ranging from 0.58% in Malawi to 6.2% in Turkey¹⁰. In the United States the prevalence is approximately 0.5–1%, in London 0.74%, in Nigeria 0.65% with right-sided ribs most common, and in India 0.6–1.22%¹¹,¹²,¹³. In Oman, prevalence has been reported at 0.94%, again with women affected more often than men¹⁴.
Associated Conditions
Thoracic Outlet Syndrome (TOS): Compression of the brachial plexus and/or subclavian artery. Cervical ribs have been associated with TOS in up to 49% of cases¹.
Neurogenic Symptoms: Brachial plexus involvement may cause paresthesia and reduced muscle strength in the hand.
Vascular Involvement: Compression of the subclavian artery may cause ischemic symptoms in the arm.
Sympathetic Involvement: In rare cases, Horner syndrome may develop if the sympathetic chain is affected⁵.
Symptoms
Local symptoms:
A palpable, firm and bony supraclavicular lump that is not mobile.
Sensory symptoms:
Paresthesia in the fingers or hand, commonly in the radial or ulnar distribution, although the entire hand may be affected.
Radiating pain down the arm.
Vascular symptoms:
A cold and clumsy hand, particularly affecting the fingers.
Cyanosis and trophic skin changes.
In severe cases, gangrene may develop.
The radial pulse may be reduced or absent.
Motor symptoms:
Reduced grip strength.
A tendency to drop objects.
Atrophy of the palmar hand muscles¹⁵,¹⁶.
Diagnosis and Treatment of Cervical Rib
Cervical ribs are uncommon in the general population, with an estimated prevalence below 1%, and are most often discovered incidentally on imaging¹⁷,¹⁸. On radiographs, cervical ribs can be distinguished from thoracic structures because their transverse processes project inferolaterally, whereas thoracic processes are directed anterolaterally. This anatomical feature can help with identification and differentiation.
Imaging
Radiography is the most common method used to identify cervical ribs, particularly anteroposterior and lateral views of the cervicothoracic junction. CT and MRI may be used when nerve or vascular compression is suspected, especially in patients with thoracic outlet syndrome. Imaging is useful both for assessing the extent of the rib and for identifying associated structural abnormalities or secondary changes.
Special Tests
Several orthopedic tests may be used as part of the clinical assessment when neurovascular compression caused by a cervical rib is suspected:
Adson's Test: Assesses potential compression of the subclavian artery at the scalene triangle. The test is considered positive if the radial pulse decreases or disappears during inspiration and rotation of the head toward the affected side.
Spurling's Test: Used to assess cervical nerve-root involvement. It is performed with lateral flexion and compression of the head and is considered positive if it reproduces pain or paresthesia.
Shoulder Abduction Test: The patient places the hand on the head with the shoulder abducted. The test is considered positive if radicular symptoms decrease, suggesting cervical nerve-root compression or cervical disc herniation.
Differential Diagnoses
When cervical rib is suspected in a patient with neurological or vascular symptoms, it is important to exclude other causes of a similar clinical presentation:
Cervical disc herniation
Cervical spondylosis
Peripheral neuropathies
Raynaud disease
Syringomyelia
Poliomyelitis
Muscular dystrophies
Motor neuron diseases
Treatment
Treatment depends on symptoms and may involve medical, surgical and physiotherapy approaches. Most asymptomatic cases require no specific treatment, but intervention may be considered when symptoms develop as a result of thoracic outlet syndrome.
1. Medical Treatment:
Use of anti-inflammatory medication and analgesics to relieve pain and reduce inflammation.
2. Surgical Treatment:
Removal of the extra rib, either partial or complete resection.
Division of the scalene muscle group, particularly in cases where muscular compression of the brachial plexus is present.
In patients with TOS, resection of the cervical rib together with the first rib may reduce recurrence of symptoms and improve long-term outcomes²⁰.
3. Physiotherapy Management:
Physiotherapy may be appropriate in symptomatic cases and should be planned according to the patient's symptoms and functional level. The goals are to reduce pain, improve circulation and strength, and optimize postural control.
Pain relief: Shortwave diathermy may be used cautiously but is contraindicated in areas with reduced sensation.
Circulation-promoting exercises: For example, grip-strength exercises to stimulate distal circulation.
Strength Training: Focus on strength, endurance and muscle tone throughout the upper extremity.
Postural Correction: Guidance on ergonomic principles and posture.
Specific Exercises: Self-resisted elevation and adduction of the scapula.
Endurance training and progression to resisted exercises for the shoulder girdle to improve function and stability²¹.
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