Cervical Rib

What is the significance of this anomaly? • Xray of the Week

Figure 1. What is the significance of this anomaly?

Figure 2. Axial and coronal CT images of the cervical spine along with 3D CT reconstruction demonstrating a right cervical rib. A. Axial CT of the cervical spine detailing a unilateral, right cervical rib at the level of C7 (red arrow) B. Axial CT image further demonstrating the unilateral right cervical rib (red arrow) C. 3D CT reconstruction of a right cervical rib arising from the transverse process of C7 (red arrow). D. Coronal CT image of the cervical spine showing unilateral cervical rib on the right (red arrow).

Discussion:

There is a total of 12 pairs of ribs that articulate with each segment of the thoracic vertebrae posteriorly and function to protect the thoracic viscera and help promote respiration. In regards to rib anatomy, the first seven pairs are considered true ribs as they attach directly to the sternum via their costal cartilage while the 8th-10th ribs are considered false ribs since their cartilages fuse and then join at the 7th rib costal cartilage to attach indirectly to the sternum. Finally, there are also ribs 11 and 12 which are considered floating due to their lack of connection to the sternum in any fashion. Another classification regarding rib structure is typical vs atypical ribs, which separates ribs 1, 11, and 12 from 2-10 due to specific anatomical features.

Cervical ribs are a rare occurrence in the population with an incidence of under 1% and are often an incidental finding on radiographic imaging (1). A cervical rib is defined as an accessory rib that develops most commonly at the level of C7, but some cases have been reported at C6, C5, and as high as C4 (1). To classify a cervical rib, there must be evidence of a supernumerary rib that attaches to the transverse process of a cervical vertebra (Figs. 1,2) (1,2). When they are bilateral, they are often asymmetric, however, when they are unilateral, they tend to be found on the right (1). Cervical ribs are normally clinically silent, and individuals may never know that they have one. However, this becomes clinically relevant and warrants investigation when patients start to develop symptoms of thoracic outlet syndrome due to compression of the brachial plexus, subclavian artery, or subclavian vein in the extremity on the side of the cervical rib (2,3). In rare cases, cervical ribs have been shown to cause recurrent strokes in younger individuals, subclavian artery aneurysms, subclavian artery thromboses, and significant ischemia leading to gangrene of the distal phalanges (4). Without clinical manifestations of a cervical rib, there is no dedicated imaging protocol to detect them. They will most likely be picked up incidentally on plain radiographs for other medical indications (1,2).

When there are clinical manifestations of thoracic outlet syndrome, an initial plain radiograph would be an appropriate first study. In the setting of unilateral ischemic arm pain, paresthesia, weakened pulse, and numbness, CT scan will definitively demonstrate a rib articulating with the transverse process of C7 if it is present (Figs. 1,2) (3). Three-dimensional computed tomography is especially useful for surgical planning purposes (Figs. 1,2 C) (5). With 3D CT, anatomical detail is significantly enhanced, especially the attachment sites of the rib, presence of pseudoarthrosis, and the location of nearby vasculature and neural structures (5).

References:

1. Spadliński Ł, Cecot T, Majos A, et al. The Epidemiological, Morphological, and Clinical Aspects of the Cervical Ribs in Humans. Biomed Res Int. 2016;2016:8034613. DOI: 10.1155/2016/8034613

2. Jeung MY, Gangi A, Gasser B, et al. Imaging of chest wall disorders. Radiographics. 1999;19(3):617-637. DOI: 10.1148/radiographics.19.3.g99ma02617

3. Viertel VG, Intrapiromkul J, Maluf F, et al. Cervical ribs: a common variant overlooked in CT imaging. AJNR Am J Neuroradiol. 2012;33(11):2191-2194. DOI: 10.3174/ajnr.A3143

4. Kataria R, Sharma A, Srivastava T, Bagaria H, Sharma A. Cervical rib, a rare cause of recurrent stroke in the young: case report. Neurologist. 2012;18(5):321-323. DOI: 10.1097/NRL.0b013e31826754a9

5. Chandak S, Kumar A. Usefulness of 3D CT in Diagnosis of Cervical Rib Presenting as Supraclavicular Swelling of Short Duration. J Clin Diagn Res. 2014;8(5):RD01-RD2. DOI:10.7860/JCDR/2014/7977.4374

Corey Stump is a medical student and aspiring radiologist at the Marian University College of Osteopathic Medicine in Indianapolis, Indiana. Prior to medical school, he graduated summa cum laude from Wittenberg University where he received a B.S. degree in Biology. He is excited to pursue a career in Diagnostic Radiology with interests in medical education. His current project involves a webinar titled “Navigating The Virtual Match; Program Directors Vs Medical Students” through the Academy of Online Radiology Education with other medical students and radiologists around the country in an effort to provide insight on the upcoming residency match. He is passionate about teaching and he hopes to provide a meaningful experience to medical students one day.

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Kevin M. Rice, MD is the president of Global Radiology CME

Dr. Rice is a radiologist with Renaissance Imaging Medical Associates and is currently the Vice Chief of Staff at Valley Presbyterian Hospital in Los Angeles, California. Dr. Rice has made several media appearances as part of his ongoing commitment to public education. Dr. Rice's passion for state of the art radiology and teaching includes acting as a guest lecturer at UCLA. In 2015, Dr. Rice and Natalie Rice founded Global Radiology CME to provide innovative radiology education at exciting international destinations, with the world's foremost authorities in their field. In 2016, Dr. Rice was nominated and became a semifinalist for a "Minnie" Award for the Most Effective Radiology Educator.

Follow Dr. Rice on Twitter @KevinRiceMD

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