Occipital Emissary Foramina in Human Adult Skull and Their Clinical Implications

Subashri. A¹*, M.S. Thenmozhi²

¹I BDS Student, Anatomy Department, Saveetha Dental College, Chennai - 600 077.

²HOD, Department of Anatomy, Saveetha Dental College, Chennai 77

*Corresponding Author E-mail: subashrikhabiya@gmail.com

ABSTRACT:

Introduction: Occipital emissary foramina is always been an area of interest for neuroanatomist. It is present in the squamous part of occipital bone at occipital protuberance. Occipital emissary vein are important source of bleeding during surgeries. Aim: To identify the occipital emissary foramina in adult human skulls and to study their clinical implications. Objective: To distinguish normal from potentially abnormal structures and to review the literature on anatomical and clinical aspects of occipital emissary foramina. Background: An occipital emissary foramina has been described by several authors. This foramina is present in the squamous part of the occipital bone at occipital protuberance and it transmits a vein that connects sigmoid sinus with the veins of sub-occipital venous plexus. Reason: Anatomical variations of foramina of skull have been of interest for neuroanatomist due to clinical consequence that these structures can cause problems especially in areas such as neurosurgery and dentistry. Conclusion: The present study revealed that occipital emissary foramina occurred more frequently than that of which was described in the literature.

KEYWORDS: Occipital, Foramina, External Occipital Protuberance, Foramen Magnum, Squamous, Skulls.

INTRODUCTION:

The veins that act as output vein of neurocranium and drainage of venous blood from the cephalic structures are the Emissary vein. The intracranial venous sinuses is connected with the extracranial Venus plexus by the emissary foramina which transmits the emissary veins. The blood flow through these veins is slow under normal circumstances. The venous sinuses are connected to the extracranial veins by the Emissary vein which cross the emissary foramina of the skull. They are valveless. Blood flows in both the directions but flow of blood away from the brain is usual. Mastoid, parietal, condyloid and the foramen of Vesalius are restricted to emissary foramina in ordinary usage. Solitary foramina which is present occasionally in the squamous part of the occipital bone at the occipital protuberance is the occipital emissary foramina^[1].

It connects the confluence of sinuses with the occipital vein by the transmission of occipital emissary vein. The occipital diploic vein is also received by the emissary vein^[2][3].In recent studies the occipital emissary foramina is found more often near foramen magnum than the external occipital protuberance^[4][5].

AIM:

This study is done to find out the incidence of foramina in skulls of Saveetha Dental College.

OBJECTIVE:

The site of the foramina will be determined to do a comparative study with the traditional and existing literature was done. The discovery of the study were then correlated to clinical manifestations that can arise due to the position and number of foramina if seen on skull.

Fig.1.1: Anatomical landmarks of the study

MATERIALS AND METHODS:

The study was done on 60 Human Adult skulls of unknown sex in the Department of Anatomy, Saveetha Dental College, Chennai. For the presence of occipital emissary foramina the squamous part of the occipital bone was studied. In the study the anatomical landmarks used are:

(1) External occipital protuberance (EOP)

(2) External occipital crest (EOC)

(3) Foramen magnum (FM).On the EOP majority of foramina were not seen. Then they were classified as left or right or on the EOC. Between the EOP and FM a horizontal line was drawn and classified as near FM or near EOP. Only when the copper wire of 0.5mm went into the skull it was said to have foramina.

RESULT:

Out of 60 skulls studied, the foramina was observed in 35/60 (58.33%) skulls, 5/35 (14.28%) to the right of EOC, 9/35 (25.71%) to the left of EOC, 3/35 (8.57%) on the EOC. In the left of EOC near the EOP one single large foramen was observed and one on the EOC near FM. In 11/35 (31.42%) the foramina was present on either sides of EOC.

Table.1.1: Number of foramina present.

Serial No	Number of foramina	Number of skulls	Percentage of no of skulls
1	Nil	25	42%
2	One	19	32%
3	Two	11	18%
4	Three	3	5%
5	Four	2	3%

Table.1.2: Location of foramina.

Study	Absent	Right of EOC	Left of EOC	On the EOC
60	25	5	9	3

Table.1.2. Cont....

Near FM	Near EOP	Bilateral	Trilateral	4 foramen
1	1	11	3	2

CONCLUSION:

Out of 60 skulls studied, the foramina was observed in 58.33%, out of which 14.28% skulls were on right side of EOC, 25.71% skulls were on left of EOC and 8.57% skulls were found on EOC

DISCUSSION:

A byproduct of anthology of bipedalism by extant humans are Emissary foramina^[8]. From the brain to the vertebral veins the delivery of blood has an upright posture necessitated, multiple hypoglossal canals, venous channels like the enlarged occipital sinus system and emissary foramina that direct the emissary veins developed^[9]. For delivering blood selectively to the vertebral plexus of veins these are considered to be in epigenetic adaptations^[10]. At low frequencies throughout the homnoid record the occipital foramen occurs near the inion^[9].

In our present study the incidence of foramina was 58.33%. This incidence were high when compared with other Indian studies. This is high if we compare it to other Indian studies. Various studies from North India have shown varying incidence ranging from a single case in 214 skulls, that is 0.46%-2.07%^[4]^-^[7]. The incidence is 2.6% in Anatolian skulls and 14% in Bangladeshi skulls^[5]. Near the posterior margin of the foramen magnum the location of foramina was seen. The incidence of foramen is 1.6% and near the EOP in a study done by Boyd^[6]. In our study,one foramina is seen near FM and one case near EOP.

Based on location, connection of occipital emissary foramina are:

(1) If seen on the EOC near the EOP confluence of sinuses with the occipital vein.

(2) If seen on either side of FM marginal sinuses to occipital vein.

(3) If seen on the EOC near the FM occipital sinus to occipital vein.

(4) May also receive the occipital diploic vein.

Table.1.3: Previous studies.

Serial No.	Study	Solitary foramen	Bilateral foramen
(1)	Boyd [1930](7)	24/1500 (1.6%)	Nil
(2)	Sharma et al. [1986](8)	1/214 (0.46%)	Nil
(3)	Premsagar et al. [1990](4)	7/338 (2.07%)	Nil
(4)	Gozil et al. [1995](5)	8/300 (2.6%)	Nil
(5)	Present study	35/60 (58.33%)	11/60

ACKNOWLEDGEMENT:

With sincere gratitude, we acknowledge the staff members of anatomy department, Mrs. M.S. Thenmozhi (HOD of Anatomy Department, Saveetha Dental College) and Saveetha Dental College for the extended support.

REFERENCES:

[1] P. K. Williams et al, in Gray’s Anatomy, pp.805, Churchill Livingston, London,37th edition,1989.

[2] W. H. Hollinshead, in Text Book of Anatomy, p.868, Harper and Row, USA, 2nd edition, 1967.

[3] D.H. Padget, “The cranial venous system in man in reference to development, adult configuration and relation to the arteries,” American Journal of Anatomy, vol. 98, pp. 307, 1956.

[4] I.C. Premsagar et al, “Occipital emissary foramen in Indian skulls,” Journal of Anatomy, vol.173, pp.188,1990.

[5] S.M.A. Hossain et al, “Occipital emissary foramen in Bangladeshi skulls,” Pakistan Journal of Medical Sciences, vol.17, no.3, pp.156,2001.

[6] G.I. Boyd, “The emissary foramina of the cranium of man and the anthropoids,” Journal of Anatomy, vol. 65, no. 1, pp.108–121,1930.

[7] P.K.Sharma et al,“Emissaryoccipitalforamen,” Anatomischer Anzeiger, vol. 162, no. 4, pp. 297–298,1986.

[8] D. Falk et al, “The cranial venous sinus system in australopithecus afarensis,” Nature, vol. 306, no. 5945, pp. 779– 781,1983.

[9] D. Falk, “Evolution of cranial blood drainage in hominids: enlarged occipital/marginal sinuses and emissary foramina,” American Journal of Physical Anthropology, vol. 70, no. 3, pp. 311–324,1986.

Received on 12.03.2016 Modified on 04.04.2016

Research J. Pharm. and Tech. 9(6):June, 2016; Page 716-718

DOI: 10.5958/0974-360X.2016.00135.9