Cervical rib

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Cervical ribs are the ribs of the neck in many tetrapods. In most mammals, including humans, cervical ribs are not normally present as separate structures. They can, however, occur as a pathology. In humans, pathological cervical ribs are usually not of clinical concern, although they can cause a form of thoracic outlet syndrome.

Contents

Development

Like other ribs, the cervical ribs form by endochondral ossification. [1]

Variation

Some sauropod dinosaurs had exceptionally long cervical ribs; a cervical rib of Mamenchisaurus sinocanadorum was 4.2 metres (14 ft) long. [2]

In birds, the cervical ribs are small and completely fused to the vertebrae.

In therian mammals, the cervical ribs fully fuse with the cervical vertebrae to form part of the transverse processes, except in rare pathological cases. In contrast, monotremes retain the plesiomorphic condition of having separate cervical ribs. [3]

Pathological cervical ribs

Cervical rib
Other namesNeck ribs [4]
Halsrippe.png
Specialty Thoracic surgery

A cervical rib in humans is an extra rib which arises from the seventh cervical vertebra. Their presence is a congenital abnormality located above the normal first rib. A cervical rib is estimated to occur in 0.2% [5] to 0.5% [6] (1 in 200 to 500) of the population. [7] People may have a cervical rib on the right, left or both sides. [8] [9]

Most cases of cervical ribs are not clinically relevant and do not have symptoms; [10] [11] cervical ribs are generally discovered incidentally, most often during x-rays and CT scans. [6] [7] [9] However, they vary widely in size and shape, [6] and in rare cases, they may cause problems such as contributing to thoracic outlet syndrome, [10] because of pressure on the nerves that may be caused by the presence of the rib. [10] [12]

A cervical rib represents a persistent ossification of the C7 lateral costal element. [10] [11] During early development, this ossified costal element typically becomes re-absorbed. Failure of this process results in a variably elongated transverse process or complete rib that can be anteriorly fused with the T1 first rib below. [13]

Diagnosis

3D CT reconstruction of a cervical rib. Halsrippe.JPG
3D CT reconstruction of a cervical rib.
Bilateral, symmetric, full, ossified cervical ribs. CervicalRibs.png
Bilateral, symmetric, full, ossified cervical ribs.

On imaging, cervical ribs can be distinguished because their transverse processes are directed inferolaterally, whereas those of the adjacent thoracic spine are directed anterolaterally. [14]

Associated conditions

The presence of a cervical rib can cause a form of thoracic outlet syndrome due to compression of the lower trunk of the brachial plexus or subclavian artery. [10] These structures become encroached upon by the cervical rib and scalene muscles.

Compression of the brachial plexus may be identified by weakness of the muscles in the hand, near the base of the thumb. Compression of the subclavian artery is often diagnosed by finding a positive Adson's sign on examination, where the radial pulse in the arm is lost during abduction and external rotation of the shoulder. [10] A positive Adson's sign is non-specific for the presence of a cervical rib however, as many individuals without a cervical rib will have a positive test. Compression of the sympathetic chain may cause Horner's syndrome.

In other animals

Recent studies have also found a high percent of cervical ribs in woolly mammoths. It is believed that the decline in mammoth numbers may have forced inbreeding within the species which in turn had increased the number of mammoths being born with cervical ribs. Cervical ribs have been connected with leukaemia in human children, so it has given scientists new evidence to believe that the mammoth's extinction was attributed to the condition. [15] They have also been interpreted as a sign of inbreeding depression in other mammals, such as Megaloceros . [16]

Related Research Articles

<span class="mw-page-title-main">Rib</span> Long bone in vertebrates that protects vital respiratory and cardiovascular organs

In vertebrate anatomy, ribs are the long curved bones which form the rib cage, part of the axial skeleton. In most tetrapods, ribs surround the thoracic cavity, enabling the lungs to expand and thus facilitate breathing by expanding the thoracic cavity. They serve to protect the lungs, heart, and other vital organs of the thorax. In some animals, especially snakes, ribs may provide support and protection for the entire body.

<span class="mw-page-title-main">Rib cage</span> Bone structure of the thorax

The rib cage or thoracic cage is an endoskeletal enclosure in the thorax of most vertebrates that comprises the ribs, vertebral column and sternum, which protect the vital organs of the thoracic cavity, such as the heart, lungs and great vessels and support the shoulder girdle to form the core part of the axial skeleton.

<span class="mw-page-title-main">Lumbar vertebrae</span> Five bones of the spine in the lower back

The lumbar vertebrae are located between the thoracic vertebrae and pelvis. They form the lower part of the human back in humans, and the tail end of the back in quadrupeds. In humans, there are five lumbar vertebrae. The term is used to describe the anatomy of humans and quadrupeds, such as horses, pigs, or cattle. These bones are found in particular cuts of meat, including tenderloin or sirloin steak.

<span class="mw-page-title-main">Phrenic nerve</span> Nerve controlling the diaphragm

The phrenic nerve is a mixed motor/sensory nerve that originates from the C3-C5 spinal nerves in the neck. The nerve is important for breathing because it provides exclusive motor control of the diaphragm, the primary muscle of respiration. In humans, the right and left phrenic nerves are primarily supplied by the C4 spinal nerve, but there is also a contribution from the C3 and C5 spinal nerves. From its origin in the neck, the nerve travels downward into the chest to pass between the heart and lungs towards the diaphragm.

<span class="mw-page-title-main">Subclavian artery</span> Major arteries of the upper thorax, below the clavicle

In human anatomy, the subclavian arteries are paired major arteries of the upper thorax, below the clavicle. They receive blood from the aortic arch. The left subclavian artery supplies blood to the left arm and the right subclavian artery supplies blood to the right arm, with some branches supplying the head and thorax. On the left side of the body, the subclavian comes directly off the aortic arch, while on the right side it arises from the relatively short brachiocephalic artery when it bifurcates into the subclavian and the right common carotid artery.

<i>Mamenchisaurus</i> Sauropod dinosaur genus from Late Jurassic-Early Cretaceous Period

Mamenchisaurus is a genus of sauropod dinosaur known for their remarkably long necks which made up nearly half the total body length. Numerous species have been assigned to the genus; however, the validity of these assignments has been questioned. Fossils have been found in the Sichuan Basin and Yunnan Province in China. Several species from the Upper Shaximiao Formation, whose geologic age is uncertain, have been described. However, evidence suggests this formation to be no earlier than the Oxfordian stage of the Late Jurassic. M. sinocanadorum dates to the Oxfordian stage, and M. anyuensis to the Aptian stage of the Early Cretaceous. Most species were medium-large to large sauropods, measuring roughly 15 to 26 meters in length—possibly up to 35 meters (115 ft), based on two undescribed vertebrae.

<span class="mw-page-title-main">Levator scapulae muscle</span> Slender skeletal muscle at the back and side of the neck

The levator scapulae is a slender skeletal muscle situated at the back and side of the neck. It originates from the transverse processes of the four uppermost cervical vertebrae; it inserts onto the upper portion of the medial border of the scapula. It is innervated by the cervical nerves C3-C4, and frequently also by the dorsal scapular nerve. As the Latin name suggests, its main function is to lift the scapula.

<span class="mw-page-title-main">Rhomboid major muscle</span> Skeletal muscle in the human back

The rhomboid major is a skeletal muscle of the back that connects the scapula with the vertebrae of the spinal column. It originates from the spinous processes of the thoracic vertebrae T2–T5 and supraspinous ligament; it inserts onto the lower portion of the medial border of the scapula. It acts together with the rhomboid minor to keep the scapula pressed against thoracic wall and to retract the scapula toward the vertebral column.

<span class="mw-page-title-main">Thoracic outlet syndrome</span> Compression of nerves or blood vessels between the neck and ribcage

Thoracic outlet syndrome (TOS) is a condition in which there is compression of the nerves, arteries, or veins in the superior thoracic aperture, the passageway from the lower neck to the armpit, also known as the thoracic outlet. There are three main types: neurogenic, venous, and arterial. The neurogenic type is the most common and presents with pain, weakness, paraesthesia, and occasionally loss of muscle at the base of the thumb. The venous type results in swelling, pain, and possibly a bluish coloration of the arm. The arterial type results in pain, coldness, and pallor of the arm.

<span class="mw-page-title-main">Pancoast tumor</span> Medical condition

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<span class="mw-page-title-main">Adson's sign</span> Medical condition

Adson's sign is the loss of the radial pulse in the arm by rotating head to the ipsilateral side with extended neck following deep inspiration.

<span class="mw-page-title-main">Cervical vertebrae</span> Vertebrae of the neck

In tetrapods, cervical vertebrae are the vertebrae of the neck, immediately below the skull. Truncal vertebrae lie caudal of cervical vertebrae. In sauropsid species, the cervical vertebrae bear cervical ribs. In lizards and saurischian dinosaurs, the cervical ribs are large; in birds, they are small and completely fused to the vertebrae. The vertebral transverse processes of mammals are homologous to the cervical ribs of other amniotes. Most mammals have seven cervical vertebrae, with the only three known exceptions being the manatee with six, the two-toed sloth with five or six, and the three-toed sloth with nine.

<span class="mw-page-title-main">Stellate ganglion</span> Component of the human nervous system

The stellate ganglion is a sympathetic ganglion formed by the fusion of the inferior cervical ganglion and the first thoracic ganglion, which is present in 80% of individuals. Sometimes, the second and the third thoracic ganglia are included in this fusion.

<span class="mw-page-title-main">Subclavian vein</span> Blood vessel that drains the arm

The subclavian vein is a paired large vein, one on either side of the body, that is responsible for draining blood from the upper extremities, allowing this blood to return to the heart. The left subclavian vein plays a key role in the absorption of lipids, by allowing products that have been carried by lymph in the thoracic duct to enter the bloodstream. The diameter of the subclavian veins is approximately 1–2 cm, depending on the individual.

<span class="mw-page-title-main">Superior thoracic aperture</span> Opening at the top of the thoracic cavity (area enclosed by the ribcage)

The superior thoracic aperture, also known as the thoracic outlet, or thoracic inlet refers to the opening at the top of the thoracic cavity. It is also clinically referred to as the thoracic outlet, in the case of thoracic outlet syndrome. A lower thoracic opening is the inferior thoracic aperture.

<span class="mw-page-title-main">Scalene muscles</span> Muscles on the sides of the neck

The scalene muscles are a group of three muscles on each side of the neck, identified as the anterior, the middle, and the posterior. They are innervated by the third to the eighth cervical spinal nerves (C3-C8).

<span class="mw-page-title-main">Subclavian steal syndrome</span> Medical condition

Subclavian steal syndrome (SSS), also called subclavian steal steno-occlusive disease, is a medical condition characterized by retrograde (reversed) blood flow in the vertebral artery or the internal thoracic artery. This reversal occurs due to proximal stenosis (narrowing) or occlusion of the subclavian artery.

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First rib resection is a surgical procedure used in humans to treat thoracic outlet syndrome (TOS) and Paget–Schroetter disease. It involves the surgical removal of a segment of the first rib, which is the rib closest to the head, under the collar bone.

<span class="mw-page-title-main">Vertebra</span> Bone in the vertebral column

Each vertebra is an irregular bone with a complex structure composed of bone and some hyaline cartilage, that make up the vertebral column or spine, of vertebrates. The proportions of the vertebrae differ according to their spinal segment and the particular species.

References

  1. ↑ Romer, Alfred Sherwood (1956). Osteology of the Reptiles.
  2. ↑ Moore, Andrew J.; Barrett, Paul M.; Upchurch, Paul; Liao, Chun-Chi; Ye, Yong; Hao, Baoqiao; Xu, Xing (2023-03-15). "Re-assessment of the Late Jurassic eusauropod Mamenchisaurus sinocanadorum Russell and Zheng, 1993, and the evolution of exceptionally long necks in mamenchisaurids". Journal of Systematic Paleontology. 21 (1). doi:10.1080/14772019.2023.2171818. ISSN   1477-2019.
  3. ↑ Weisbecker, Vera (2011). "Monotreme ossification sequences and the riddle of mammalian skeletal development". Evolution. 65 (5): 1323–1335. doi:10.1111/j.1558-5646.2011.01234.x. eISSN   1558-5646. ISSN   0014-3820.
  4. ↑ Selim, Jocelyn. "Useless Body Parts".
  5. ↑ Galis F (1999). "Why do almost all mammals have seven cervical vertebrae? Developmental constraints, Hox genes, and cancer". J. Exp. Zool. 285 (1): 19–26. doi:10.1002/(SICI)1097-010X(19990415)285:1<19::AID-JEZ3>3.0.CO;2-Z. PMID   10327647. Archived from the original on 2013-01-06.
  6. 1 2 3 Terry Yochum; Lindsay Rowe (2005). Essentials of Skeletal Radiology (3 ed.). Lippencott & Williams.
  7. 1 2 Rochkind, Shimon; Zager, Eric (2012-01-01), Quiñones-Hinojosa, Alfredo (ed.), "Chapter 205 - Management of Thoracic Outlet Syndrome", Schmidek and Sweet Operative Neurosurgical Techniques (Sixth Edition), Philadelphia: W.B. Saunders, pp. 2339–2348, doi:10.1016/b978-1-4160-6839-6.10205-9, ISBN   978-1-4160-6839-6 , retrieved 2020-10-23
  8. ↑ Oner, Zulal; Oner, Serkan; Sahin, Necati Emre; Cay, Mahmut (26 January 2023). "Evaluation of congenital rib anomalies with multi-detector computed tomography in the Turkish population". Folia Morphologica. doi: 10.5603/FM.a2023.0006 . PMID   36794687. S2CID   256899032.
  9. 1 2 Walden, Michael; et al. (2013). "Cervical ribs: identification on MRI and clinical relevance". Clinical Imaging. 37 (5): 938–941. doi:10.1016/j.clinimag.2013.01.005. PMID   23759210.
  10. 1 2 3 4 5 6 Giles, Lynton G. F. (2009-01-01), Giles, Lynton G. F. (ed.), "Case 67 - Cervical ribs", 100 Challenging Spinal Pain Syndrome Cases (Second Edition), Edinburgh: Churchill Livingstone, pp. 311–314, doi:10.1016/b978-0-443-06716-7.00067-0, ISBN   978-0-443-06716-7 , retrieved 2020-10-23
  11. 1 2 Tani, Edneia M.; Skoog, Lambert (2008-01-01), Bibbo, Marluce; Wilbur, David (eds.), "CHAPTER 22 - Salivary Glands and Rare Head and Neck Lesions", Comprehensive Cytopathology (Third Edition), Edinburgh: W.B. Saunders, pp. 607–632, ISBN   978-1-4160-4208-2 , retrieved 2020-10-23
  12. ↑ Guttentag, Adam; Salwen, Julia (1999). "Keep Your Eyes on the Ribs: The Spectrum of Normal Variants and Diseases That Involve the Ribs". RadioGraphics. 19 (5): 1125–1142. doi:10.1148/radiographics.19.5.g99se011125. PMID   10489169.
  13. ↑ E. McNally, B. Sandin & R. A. Wilkins (June 1990). "The ossification of the costal element of the seventh cervical vertebra with particular reference to cervical ribs". Journal of Anatomy . 170: 125–129. PMC   1257068 . PMID   2123844.
  14. ↑ Balan, Nisha Sharma, Anu (2008). Get through FRCR part 2B : rapid reporting of plain radiographs. London: Royal Society of Medicine. ISBN   978-1853157547.{{cite book}}: CS1 maint: multiple names: authors list (link)
  15. ↑ "Woolly Mammoths Suffered Major Birth Defects Before Extinction". IFLScience. 25 March 2014.
  16. ↑ Cuxart-Erruz, Raimon; Van Dooren, Tom J. M.; van der Geer, Alexandra A. E.; Galis, Frietson (2024-09-24). "Increased incidences of cervical ribs in deer indicate extinction risk". Proceedings of the National Academy of Sciences. 121 (39): –2406670121. doi:10.1073/pnas.2406670121.
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