Cervical ribsare theribsof theneckin manytetrapods.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 ofthoracic outlet syndrome.
Development
editLike other ribs, the cervical ribs form byendochondral ossification.[1]
Variation
editThe cervical ribs ofsauropoddinosaurswere extended by ossifiedtendons,[2]and could reach exceptional lengths; a cervical rib ofMamenchisaurus sinocanadorumwas 4.2 metres (14 ft) long.[3]
Inbirds,the cervical ribs are small and completely fused to the vertebrae.
Intherianmammals,the cervical ribs fully fuse with thecervical vertebraeto form part of thetransverse processes,except in rare pathological cases. In contrast,monotremesretain the plesiomorphic condition of having separate cervical ribs.[4]
Pathological cervical ribs
edit| Cervical rib | |
|---|---|
| Other names | Neck ribs[5] |
 | |
| Specialty | Thoracic surgery |
Acervical ribin humans is anextraribwhich arises from the seventhcervical vertebra.Their presence is acongenitalabnormality located above the normal first rib. A cervical rib is estimated to occur in 0.2%[6]to 0.5%[7](1 in 200 to 500) of the population.[8]People may have a cervical rib on the right, left or both sides.[9][10]
Most cases of cervical ribs are not clinically relevant and do not have symptoms;[11][12]cervical ribs are generally discoveredincidentally,most often duringx-raysandCT scans.[7][8][10]However, they vary widely in size and shape,[7]and in rare cases, they may cause problems such as contributing tothoracic outlet syndrome,[11]because of pressure on thenervesthat may be caused by the presence of the rib.[11][13]
A cervical rib represents a persistentossificationof the C7 lateral costal element.[11][12]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.[14]
Diagnosis
edit
On imaging, cervical ribs can be distinguished because their transverse processes are directed inferolaterally, whereas those of the adjacent thoracic spine are directedanterolaterally.[15]
Associated conditions
editThe presence of a cervical rib can cause a form ofthoracic outlet syndromedue to compression of the lower trunk of thebrachial plexusorsubclavian artery.[11]These structures become encroached upon by the cervical rib andscalene 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 positiveAdson's signon examination, where the radialpulsein the arm is lost duringabductionandexternal rotationof theshoulder.[11]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 causeHorner's syndrome.
In other animals
editRecent 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 withleukaemiain human children, so it has given scientists new evidence to believe that the mammoth's extinction was attributed to the condition.[16]They have also been interpreted as a sign ofinbreeding depressionin other mammals, such asMegaloceros.[17]
References
edit- ^Romer, Alfred Sherwood (1956).Osteology of the Reptiles.
- ^Klein, Nicole; Christian, Andreas; Sander, P. Martin (2012-12-23)."Histology shows that elongated neck ribs in sauropod dinosaurs are ossified tendons".Biology Letters.8(6):1032–1035.doi:10.1098/rsbl.2012.0778.eISSN1744-957X.ISSN1744-9561.PMC3497149.PMID23034173.
- ^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 Palaeontology.21(1).Bibcode:2023JSPal..2171818M.doi:10.1080/14772019.2023.2171818.ISSN1477-2019.
- ^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.eISSN1558-5646.ISSN0014-3820.PMID21521190.
- ^Selim, Jocelyn."Useless Body Parts".
- ^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.Bibcode:1999JEZ...285...19G.doi:10.1002/(SICI)1097-010X(19990415)285:1<19::AID-JEZ3>3.0.CO;2-Z.PMID10327647.Archived fromthe originalon 2013-01-06.
- ^abcTerry Yochum; Lindsay Rowe (2005).Essentials of Skeletal Radiology(3 ed.). Lippencott & Williams.
- ^abRochkind, 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,ISBN978-1-4160-6839-6,retrieved2020-10-23
- ^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.83(1):182–191.doi:10.5603/FM.a2023.0006.PMID36794687.S2CID256899032.
- ^abWalden, 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.PMID23759210.
- ^abcdefGiles, 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,ISBN978-0-443-06716-7,retrieved2020-10-23
- ^abTani, 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,ISBN978-1-4160-4208-2,retrieved2020-10-23
- ^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.PMID10489169.
- ^ 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.PMC1257068.PMID2123844.
- ^Balan, Nisha Sharma, Anu (2008).Get through FRCR part 2B: rapid reporting of plain radiographs.London: Royal Society of Medicine.ISBN978-1853157547.
{{cite book}}:CS1 maint: multiple names: authors list (link) - ^"Woolly Mammoths Suffered Major Birth Defects Before Extinction".IFLScience.25 March 2014.
- ^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.Bibcode:2024PNAS..12106670C.doi:10.1073/pnas.2406670121.PMC11441530.PMID39284067.