Introduction:-In the thorax there are normally 11 pairs of intercostal spaces, that contain intercostal muscles, intercostal nerves and vessels. Bifurcation of the ribs and presence of additional intercostal spaces is a rare variation of the thoracic wall .This may be due to defect in the process of segmentation of the developing somites.

Case Report:- During a routine dissection for undergraduate medical students ,we observed a variation involving the right 4^th and 5^th ribs and its costal cartilages in the human cadaver of a man of Indian ethnicity aged about 55 years. The right 4^th and 5^th ribs and their costal cartilages were bifurcated at their costochondral junction enclosing two small circular additional intercostal spaces. Muscles covered with deep fascia were present in these circular intercostal spaces. Muscles received nerve supply from the collateral branches of 3^rd and 4^th intercostal nerves respectively.

Conclusion:-These anomalies may remain asymptomatic, can create misinterpretations during radiological or physical examinations. The knowledge about these variations will be helpful to reduce incidences of misinterpretations.

Keywords:- rib bifurcation, intercostal space, Gorlin’s syndrome.

1.      White TD,Folkens PA:Human Osteology. 2^nd edition .San Diego: Academic Press, 2000:29.

2.      Guttentag AR ,Salwen JK. Keep your eyes on ribs:the spectrum of normal variants and diseases that involve the ribs. Radiographics 1999;19:1125-1142.

3.      Gupta V, Suri RK,Rath G,Loh H. Synostosis of first and second thoracic ribs: Anatomical and radiological assessment. Int J Anat Var (IJAV). 2009; 2:131-133.

4.      Bergman R, Thompson S,Afifi A,Saadeh F. Compendium of Human Anatomic Variation. Bal to more, Urban & Schwarzenberg.1988:593.

5.      Charles I, Scott J. Pectoral girdle, spine, ribs, and pelvic girdle. In: Stevenson RE, Hall JG, Goodmann RM, eds. Human Malformations and Related Anomalies. Vol. 2. New York, Oxford University Press. 1993; 655–697.

6.      Wattanasirichaigoon D,Prasad C, Schneider G,Evans JA, Korf BR.Rib Defects in patterns of multiple malformations. a retrospective review and phenotypic analysis of 47 cases.Am J Med Gene A.2003:122A:63-69.

7.      Bitar GJ,Herman CK,Dahman MI,Hoard MA. Basal cell nevus syndrome: guidelines for early dissection. Am Fam Physician.2002; 65:2501-2504.

8.      Gorlin RJ, Goltz RW.Multiple nevoid basal-cell epithelioma, jaw cysts and bifid rib.A syndrome.N Engl J Med. 1960; 262:908-912.

9.      Lo Muzio L .Nevoid basal cell carcinoma syndrome (Gorlin syndrome).Orphanet J Rare Dis.2008;3:32.

12. Osawa T, Sasaki T, Matsumoto Y, Tsukamoto A, Onodera M, Nara E, Chen JK, Fujimura A, Nozaka Y. Bifid ribs observed in the third and the fourth ribs. Kaibogaku Zasshi. 1998; 73: 633–635.

Dr. Deepshikha Singh

Junior Resident, Department of Anatomy

IMS, BHU, Varanasi-221005, Mob.9532188506

Email-This email address is being protected from spambots. You need JavaScript enabled to view it.