Cervical Rib Diagnosis: Understanding Symptoms, Types, and Treatment Options

A cervical rib is an extra rib that develops in the neck area, above the first rib. It’s a congenital condition, meaning present from birth, and is essentially an overgrowth of the bony part of a vertebra in the cervical spine. While cervical ribs are relatively uncommon, occurring in about 0.5% to 1% of the population, most people who have them are unaware. In many cases, a cervical rib causes no problems and remains clinically insignificant throughout a person’s life. However, when symptoms do arise, often due to compression of nearby nerves and blood vessels, accurate Cervical Rib Diagnosis becomes crucial for effective management and treatment. This article delves into the intricacies of cervical ribs, exploring their structure, potential symptoms, diagnostic methods, and available treatment options.

Anatomy and Function of Cervical Ribs

Typically connected to the seventh cervical vertebra (C7), cervical ribs can vary significantly in size and shape. They can appear on one side of the body (unilateral) or both (bilateral). Each cervical rib is composed of three main parts: the head, neck, and tubercle. Posteriorly, it connects via a fibrous band to the first rib, near the insertion point of the anterior scalene muscle. For a growth to be classified as a true rib, it must articulate with the transverse process of the vertebra. Interestingly, unilateral cervical ribs are more frequently observed on the left side of the body.

Cervical ribs are classified into four types based on their development and attachment:

Type 1 (Complete Rib): This type is a fully formed rib that articulates with either the first rib or the manubrium (the upper part of the sternum).
Type 2 (Incomplete Rib with Free Distal Tip): An incomplete rib that ends in a free, unattached tip.
Type 3 (Incomplete Rib with Fibrous Band Attachment): Similar to Type 2, but the distal tip is connected to other structures via a fibrous band.
Type 4 (Short Bony Extension): A small bony outgrowth extending from the C7 transverse process.

It’s important to note that cervical ribs serve no physiological function in the body. They are essentially anatomical variations that, in most cases, do not impact bodily functions.

Embryological Origins of Cervical Ribs

The development of the skeletal system begins in the mesoderm, one of the primary germ layers in early embryo development. Specifically, cells from the paraxial mesoderm form somites on both sides of the neural tube. These somites further divide into sclerotome (ventral portion) and dermatome (dorsal portion). Sclerotome cells transform into mesenchymal cells, which are the precursors to ribs. The formation and positioning of these ribs are guided by Hox genes and growth differentiation factor 11 (GDF11). Research suggests that mutations in these crucial regulatory genes can lead to abnormal rib development, including the formation of cervical ribs ¹.

During normal embryonic development, the costal elements of mesenchymal cells located in the cervical region typically undergo atrophy (shrink and disappear). However, when this atrophy fails to occur, these elements can ossify (turn into bone), resulting in an elongated transverse process or a fully formed cervical rib. Sometimes, a cervical rib may not be long enough to reach the sternum, and instead, it may fuse anteriorly with the first thoracic rib (T1), effectively sitting above the first rib.

Impact on Blood Vessels: Vascular Compression

After nerve compression, the most significant clinical concern related to cervical ribs is the potential compression of the subclavian artery. This artery is a major blood vessel supplying the arm. Complete cervical ribs are more likely to cause subclavian artery compression than incomplete ones. When the subclavian artery is compressed, it can lead to a range of vascular symptoms, including:

Diminished or absent pulse in the affected arm.
Prolonged capillary refill time (the time it takes for color to return to the nail bed after pressure is applied).
Discoloration of the hand and fingers (paleness or bluish tint).
Decreased temperature in the distal upper extremity (cold hand and fingers).
In severe, untreated cases, gangrenous changes (tissue death) at the fingertips ².

A diagnostic test called the Adson test can help identify subclavian artery compression. A positive Adson test, performed during hyperabduction (raising and extending) of the shoulder, suggests that a cervical rib is compressing the subclavian artery.

Neurological Complications: Nerve Compression

Cervical ribs can also lead to neurological symptoms by compressing nerves of the brachial plexus. Incomplete cervical ribs are more frequently implicated in brachial plexus compression than complete ribs. The inferior trunk of the brachial plexus, specifically the C8 and T1 nerve roots, is most commonly affected ³. Compression of these nerves can result in:

Weakness in the muscles of the hand and forearm.
Clawing of the middle, ring, and little fingers (a characteristic deformity of the hand).
Numbness and tingling sensations radiating down the arm into the fingers.

When considering cervical rib diagnosis for neurological symptoms, it’s essential to rule out other conditions that can cause similar symptoms, such as carpal tunnel syndrome, ulnar nerve entrapment at the elbow, and cervical disc herniation. A thorough differential diagnosis is crucial for accurate identification of the underlying cause.

The Role of Scalene Muscles

The scalene muscles in the neck, alongside cervical ribs, can contribute to thoracic outlet syndrome (TOS). TOS is a condition characterized by compression of nerves and/or blood vessels in the space between the collarbone and the first rib (the thoracic outlet). In some cases of cervical rib resection surgery, a scalenectomy (surgical removal of a scalene muscle) may also be performed to relieve pressure in the thoracic outlet.

Physiological Variations in Cervical Ribs

Cervical ribs can present in various forms. While most commonly associated with the C7 vertebra, they can also originate from C5 and C6 vertebrae, and cases of multiple cervical ribs at different levels have been documented. These variations highlight the spectrum of anatomical presentations of cervical ribs.

Surgical Treatment Options

If conservative treatments for thoracic outlet syndrome caused by a cervical rib fail to provide relief, surgical intervention becomes necessary. The primary surgical approach is the complete resection (removal) of the cervical rib. However, the specific surgical approach can vary. The most common approaches include:

Supraclavicular Approach: Incision above the clavicle (collarbone). This approach is often preferred for cases involving arterial compression. It provides excellent access to the proximal subclavian artery, allowing for visualization and control, especially if there are arterial aneurysms or stenoses associated with the cervical rib compression. The supraclavicular approach minimizes the need to dissect through muscles and facial structures to reach the cervical rib. It also facilitates scalenectomy and the removal of any bony or myofascial abnormalities. Functional recovery rates are typically high with this approach.
Transaxillary Approach: Incision in the axilla (armpit). This is the most frequently used approach, particularly for subclavian/axillary venous occlusion or neurological compression. The transaxillary approach is advantageous because it involves less manipulation of the brachial plexus and related nerves, potentially reducing perioperative complications ⁵. It also results in a less noticeable and less painful scar compared to the supraclavicular approach. This approach is even suitable for muscular or obese patients.
Posterior Approach: Incision on the back. This approach is typically reserved for re-operations for decompression of the brachial plexus and vascular structures. The rib is removed posteriorly, behind the nerve root, with the arm adducted (brought towards the body), minimizing contact between the rib and the nerve.

Resection of cervical ribs for thoracic outlet syndrome is generally considered a safe and effective procedure. Both short-term and long-term outcomes are generally positive, with a low rate of symptom recurrence ⁶. In some cases, the first rib may also need to be resected along with the cervical rib. Studies have shown that removing both ribs does not increase morbidity or mortality compared to removing only the cervical rib.

Clinical Significance and Diagnosis of Cervical Ribs

In the majority of instances, cervical ribs are discovered incidentally during imaging tests, such as chest or cervical X-rays, performed for unrelated reasons. Symptomatic cervical ribs are relatively rare. When symptoms do occur, they are typically due to the compression of local structures, including the lower brachial plexus, subclavian artery, or subclavian vein, leading to thoracic outlet syndrome. Neurological symptoms are the most common presenting complaint in TOS related to cervical ribs.

Symptoms of nerve compression often manifest as numbness and tingling in the little and ring fingers, following the distribution of the ulnar nerve (C8 and T1 nerve roots). Subclavian artery compression can lead to a diminished pulse and changes in color and temperature in the affected arm. Subclavian vein compression can cause swelling and bluish discoloration of the affected limb, as blood return to the heart is impaired.

Cervical ribs are most often diagnosed in middle-aged adults. Factors that can predispose individuals to developing symptoms include trauma, repetitive overuse of the arm and shoulder, and poor posture. The compression of neurovascular structures by a cervical rib often occurs against the scalene muscles. A physical examination maneuver, the Adson maneuver (turning the neck to the opposite side while extending the neck), can be used to assess for subclavian artery compression. If the pulse in the affected arm diminishes or disappears during this maneuver, it suggests potential arterial compression.

Further diagnostic evaluation for cervical rib diagnosis and thoracic outlet syndrome may include:

Imaging Studies:
- X-rays: To visualize the cervical rib itself.
- CT scans: Provide more detailed bony anatomy and can help assess the relationship of the rib to surrounding structures.
- MRI scans: Useful for evaluating soft tissues, including nerves and blood vessels, and can help rule out other causes of symptoms.
Nerve Conduction Studies: To assess the function of the nerves in the brachial plexus and identify nerve compression.

Initial treatment for nerve compression is typically conservative, involving physical therapy to improve posture, strengthen muscles, and relieve pressure on nerves and blood vessels. If conservative treatment fails to alleviate symptoms, surgical removal of the cervical rib and potentially excision of the scalene muscles may be necessary. In cases of complete subclavian artery occlusion, a bypass graft may be required to restore blood flow.

It’s important to note a less common but significant association: individuals with Hox gene abnormalities that lead to cervical anomalies, including cervical ribs, have also been linked to an increased risk of certain cancers. Germ cell tumors, astrocytoma, and acute lymphoblastic leukemia (ALL) have been observed at a higher rate in children with cervical ribs and other cervical spine anomalies ⁷. While this association is important to recognize, it is crucial to remember that the vast majority of individuals with cervical ribs will not develop these cancers.

Figure: Anatomical depiction of a cervical rib. Image courtesy of S Bhimji MD.

Review Questions

(Original review questions would be included here if needed, but are omitted for brevity in this rewritten SEO-focused article).

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Disclosures: (Original disclosures are kept as is)

Disclosure: Brian Fliegel declares no relevant financial relationships with ineligible companies.

Disclosure: Ritesh Menezes declares no relevant financial relationships with ineligible companies.