1

The National Ribat University

Faculty of Graduate Studies & Scientific Research

A Cadaveric Study of the Level of Bifurcation of the

Common Carotid Artery in Sudanese People

A Thesis Submitted in Partial Fulfillment required for the M.Sc.

in Human Clinical and Anatomy

By: FathElrahman Abu Elgasim Ibrahim Ablelaziz

Supervisor: Dr. MuhammedAhmedAbulnor

2016

I

DEDICATION

To my lovingly respected parents

To my teachers

To my colleagues.

II

ACKNOWLEDGEMENT

I would like to express my deepest gratitude to my supervisor Dr.

Mohammed Abu-Elnoor, for his excellent guidance, caring, patience, and

providing me with an excellent atmosphere for doing this research.

Also, I would like to thank my friends and appreciate all of those who in a way

or another facilitated this study.

III

TABLE OF CONTENTS

Content

Page No.

Dedication I

Acknowledgment II

Contents III

List of Figures V

List of photographs VI

Abbreviations VII

Abstract( Arabic) VIII

Abstract(English) IX

Chapter one:

1.Introduction& objectives 1

1.1 Anatomy of common carotid artery 1

1.2 Justification 1

1.3 Research objectives 2

Chapter Two:

2. Literature review 3

2.1 Anatomy of common carotid artery 3

2.2 Pathophysiology of carotid atherosclerosis 4

2.3 Imaging of common carotid arteries 6

2.4Previous studies 8

Chapter three:

3. Materials and Methods 10

Chapter four:

IV

4. Results 12

ChapterFive:

5. Discussion 19

Chapter Six:

6. Conclusion & recommendations

6.1 Conclusion 22

6. 2 Recommendations 22

Chapter Seven:

7. References 23

8. Annex

V

TABE OF FIGURES

Figure No. Title Page No.

4.1 Levels of bifurcation of the common carotid artery. 13

4. 2 Origins of the superior thyroid artery. 14

4. 3 Levels of bifurcation of the common carotid artery

in the right and left sides.

16

4.4 Origins of the superior thyroid artery in the right

and left sides.

17

VI

TABLE OF PHOTOGRAPHS

Photograph No. Title Page No.

4.1 Normal level of bifurcation of the common carotid

artery at the level of upper border of thyroid

cartilage.

18

4. 2 Low level of bifurcation of the common carotid

artery below the upper border of thyroid cartilage.

18

4. 3 High level of bifurcation of the common carotid

artery above the upper border of thyroid cartilage

and origin of superior thyroid artery from external

carotid artery.

19

4.4 Origin of superior thyroid artery. From bifurcation

of the common carotid artery.

19

4.5 Origin of superior thyroid artery from common

carotid artery.

20

VII

ABBREVIATION

SPSS Statistical Package for the Social Sciences

CCA Common Carotid Artery

ECA External Carotid Artery

ICA Internal Carotid Artery

STA Superior Thyroid Artery

CT Computed Tomography

MIP Maximum Intensity Projection

MRI Magnetic resonance imaging

TR Repetition Time

TE Echo Time

VIII

الاية

ٹ ٹ

چ چ چ ڇ ڇ ڇ ڇ ڍ ڍ ڌ ڌ ڎ ڎ ڈ ڈ ژ ژ ڑ چ

چڑ ک ک ک ک گ گ

صدق الله العظيم

٥ - ١العلق:

VIII

الخلاصة

:خلفية

إصابة .للمخ وصول الدم التي تساهم في المصادر الرئيسية هو واحد من المشترك ألسباتي الشريان

الاختلافات معرفة أن.كثيرا تخشى المضاعفات التي يؤدي إلى قد الأمامية الرقبة خلال عمليات فروعه

من المنخفضة التشعب مع في حالات الأمامية الرقبة نهج خلال المشترك ألسباتي في الشريان التشريحية

.هذه الفروعل تفادي وقوع إصابات المشترك ألسباتي الشريان

:الهدف

الاختلاف تحديد السودانيين في المشترك ألسباتي الشريان التشعب من في مستوى الاختلافات دراسة

.الأكثر شيوعا

الطرق والوسائل:

بولاية الخرطوم ولوحظت مستويات جثة محنطة ثنائيا في كليات الطب 30تم تشريح ما مجموعه

تشعبات الشرايين السباتية المشتركة وموقع منشأ الشريان الدرقي العلوي ثم تم تحليل البيانات بإستخدام

.SPSSبرنامج

النتيجة:

ية )فوق (، عال٪36.6عينة ) 22أظهرت نتائج هذه الدراسة أن مستوى التشعب كانت طبيعية في

(.٪ 1.6( ومنخفضة في عينة واحدة )٪61.6عينة ) 37مستوى الحد العلوي من الغضروف الدرقي( في

(، من من ٪50جثة ) 30تم العثور على أصل الشريان الدرقي العلوي من الشريان السباتي الخارجي في

المشترك في جثة واحده ( ومن الشريان السباتي ٪46.6جثة ) 28تشعب الشريان السباتي المشترك في

(3.3٪)

الخلاصة:

أظهرت هذه الدراسة أن المستوي الأكثر شيوعا من تشعب الشريان السباتي المشترك في الشعب

السوداني كان في مستوى أعلى. كان هناك تباين في جانب منشأ الشريان الدرقي العلوي بين الجانبين

الأيمن والأيسر.

IX

ABSTRACT

Background The common carotid artery is one of the major source that

contributes to the blood supply of the brain. Injury to the branches of the

common carotid artery during anterior cervical operation results in

complications that very much feared. Knowing the anatomic variations of the

common carotid artery during the anterior cervical approach for cases with low

– lying bifurcation of the common carotid artery would prevent injuries of these

branches.

Aim: To study the variations of the level of bifurcation of the common carotid

artery and origin of superior thyroid artery in Sudanese population.

Material & methods: a total of 30 embalmed cadavers were dissected

bilaterally in dissection rooms of faculties of medicine in Khartoum state, and

the level of bifurcations of CCA according to the level of upper border of

thyroid cartilage and site of origin of the superior thyroid artery were assessed

then the data were analyzed by using SPSS-16 software.

Results: The results of this study showed that the level of bifurcation were

normal(upper border of thyroid cartilage) in 22 cases (36.6%), high (above the

level of the upper border of thyroid cartilage) in 37 cases (61.6%) and low in

one cases (1.6 %).

The origin of superior thyroid artery, was found that from the ECA in 30

cadavers (50%), from bifurcation of the CCA in 28 cadavers (46.6%) and from

the CCA in 2 cadaver (3.3%).

Conclusion: This study showed that the commonest level of bifurcation of

CCA in Sudanese populations was found that at higher level. There was

variation in the site of origin of superior thyroid artery between right &left

sides.

X

Chapter One

INTRODUCTION & OBJECTIVE

1

1. INTRODUCTION:

1.1. Anatomy of common carotid artery

The left common carotid artery arises from the aortic arch in front and to the

right of the origin of the left subclavian artery. The right common carotid

begins behind the right sternoclavecular joint at the bifurcation of

brachiocephalic artery. [1].

The common carotid artery usually bifurcates at the level of the upper border of

the lamia of the thyroid cartilage (upper border of C4 vertebra) into the external

and internal carotid arteries [2].

The carotid pulse can be felt by pressing backwards between the trachea and

lower larynx medially and sternocleidomastoid laterally, pressing the artery

against the anterior tubercle of the transverse process of C6 vertebra [2].

1.2. Justification

The common carotid artery its one of major source that contributes to blood

supply of the brain. Injury to the branches of the common carotid artery during

anterior cervical operation results in complication that very much feared.

Knowing the anatomic variations of the common carotid artery during the

anterior cervical approach for cases with low lying bifurcation of the common

carotid artery would prevent injuries of these branches .although there is many

studies was done about the bifurcation of the common carotid artery in deferent

countries and there is no clear data about this study in Sudan, so that this study

is institution based looks for the variation in the level of bifurcation of common

carotid artery.

2

1.3. Objectives:

1.3.1.General objectives:

To study the variations in the bifurcation of the common carotid artery in

Sudanese populations.

1.3.2. Specific objectives

-To determine the commonest level of bifurcation of common carotid artery.

- To determine the origin of the superior thyroid artery.

3

Chapter Two

LITERATURE REVIEW

3

2. LITERATURE REVIEW:

2.1. Anatomy of common carotid artery

The left common carotid artery arises from the aortic arch in front and to the

right of the origin of the left subclavian artery. It passes behind the left

sternoclavicular joint, ling in its thoracic course at first in front and then to the

left side of the trachea with the left lung and pleura, the vagus and the phrenic

nerves as its lateral relations. The right common carotid begins behind the right

sternoclavecular joint at the bifurcation of brachiocephalic artery. In the neck,

each common carotid artery lies on the cervical transverse processes, separated

from them by prevertebral muscles [1].

It lies within the medial part of the carotid sheath, with the internal jugular vein

lateral to it and the vagus nerve deeply placed between the two vessels. The

sympathetic truck is behind the artery and outside the sheath, which is

overlapped superficially by the infrahyoid muscles and sternocleidomastoid.

Medial to the sheath is the trachea and esophagus and, at a higher level, the

larynx and pharynx. The thyroid gland overlaps the sheath anteromedially and

the inferior thyroid artery crosses from the thyrocervical trunk to the gland

behind the sheath [1].

The common carotid artery usually bifurcates at the level of the upper border of

the lamia of the thyroid cartilage (upper border of C4 vertebra) into the external

and internal carotids; it may do so higher near the tip of the greater horn of the

hyoid bone (C3 vertebra). The terminal portion of the artery is often dilated into

the carotid sinus, which includes the commencement of the internal carotid

artery [2].

4

Peculiaritiesas to point of division. in the majority of abnormal cases this

occurs higher than usual, the artery dividing opposite or even above the hyoid

bone; more rarely, it occurs below, opposite the middle of the larynx, or the

lower border of the cricoid cartilage; one case is related by Morgagni, where the

artery was only 4cm.in length and divided at the root of the neck. Very rarely,

the common carotid ascends in the neck without any subdivision, either the

external or the internal carotid beingwanting, and in a few cases the common

carotid has been found to be absent, the external and internal carotids arising

directly from the arch of the aorta. This peculiarity existed on both sides in

some instances, on one side in others [3].

The carotid pulse can be felt by pressing backwards between the trachea and

lower larynx medially and sternocleidomastoid laterally, pressing the artery

against the anterior tubercle of the transverse process of C6 vertebra [2].

The surface marking of the common carotid artery is along a vertical line from

the sternoclavecular joint to the level of upper border of the thyroid cartilage.

The vessel can be surgically exposed by retracting the lower part of

sternocleidomastoid backwards and incising the carotid sheath [2].

2.2. Pathophysiology of carotid atherosclerosis:

The carotid bifurcation is one of the most common sites of atherosclerotic

plaque. [4], [5].However, there is considerable variation, both between and within

individuals, in the development of plaque. Given the same systemic risk factors

for atheroma, why when the systemic risk factors for atherosclerosis should

affect both bifurcations equally, that the extent of carotid plaque is often so

5

asymmetrical within individuals?[6], [7] One possible explanation for these

observations is that vessel anatomy influences plaque development.

The symptoms and pathologic substrate of carotid artery atherosclerotic

occlusive disease were first described by C Miller Fisher in 1951 [8]. He related

atherosclerotic disease at the carotid bifurcation to ischemic symptoms in the

ipsilateral eye and brain. The modern era has seen an extraordinary expansion

in our approach to the diagnosis and management of patients with carotid artery

stenosis.Stroke, due to atherothrombosis of the extracranial carotid arteries, is

caused by a combination of factors involving the blood vessels, the clotting

system, and hemodynamics. This interaction explains the mechanism of

ischemic stroke in patients with carotid atheroma which may be due to artery-

to-artery embolism or low cerebral blood flow [8].

Carotid atherosclerosis is usually most severe within 2 cm of the bifurcation of

the common carotid artery, and predominantly involves the posterior wall of the

vessel. The plaque encroaches on the lumen of the internal carotid artery and

often extends caudally into the common carotid artery. An hourglass

configuration to the stenosis typically develops with time. Regardless of their

location, carotid plaques were associated with an increased risk of stroke in an

observational study of elderly men and women [9] and an increased risk of

mortality in an observational study of elderly men [10]. In addition to a reduction

in vessel diameter induced by the enlarging plaque, thrombus can become

superimposed on the atheroma which will further increase the degree of

stenosis. Thus, the mechanism of stroke may be embolism of the thrombotic

material or low flow due to the stenosis with inadequate collateral

compensation [8, 11].

6

2.3. Imaging of common carotid arteries:

Carotid Angiography:

Carotid angiography, also called carotid angiogram or an arteriogram, is an

invasive X-ray imaging procedure used to detect the presence of narrowing or

blockage (atherosclerosis) in the carotid arteries and determine your risk for

future stroke. Carotid angiography may be performed when carotid artery

disease is suspected, based on the results of other tests, such as a carotid duplex

ultrasound, computed tomography angiogram (CTA) or magnetic resonance

angiogram (MRA) [12].

Carotid Computed Tomography

Axial computed tomography (CT) scanning of the cerebral circulation provides

an accurate means of assessing stenosis and carotid plaque. Although early

attempts to apply CT scanning in the evaluation of the carotid artery were

limited by movement artifacts and thick scanning sections. Intravenous contrast

material must be injected rapidly enough (3-4 mL/s for a total volume of 120-

150 mL of 300-320 mg/mL nonionic contrast agent) to achieve a contrast

density of at least 150 HU or in the innominate and carotid inflow to continuing

distally into the intracranial carotid artery. Imaging begins just before the

contrast density peaks in the carotid artery [13,14,15]. Initially, all images should

be reviewed in the axial plane. Multiplanar and curved multiplanar reformatted

images are often helpful. The intraluminal diameter should be measured by

using an electronic workstation with electronic calipers. If the image of the

carotid artery is enlarged before measurement, error is reduced. Measurements

are made across the lumen through the narrowest portion of the proximal ICA

7

and across the area of the ICA that is above the stenosis and is believed to be

normal [16].

Carotid Magnetic Resonance Imaging

Time-of-flight imaging is performed without an intravenous contrast agent by

using a spoiled gradient-echo sequence. The images are displayed with an MIP

protocol in multiple projections. Because of the effects of turbulence, 3D time-

of-flight imaging tends to cause overestimation of high-grade stenoses. In some

cases, an area of discontinuity may be generated in the area of the stenosis. This

results from turbulent blood flow patterns at the point of a high-grade stenosis

and within very stenotic longer stenoses[16]. Contrast-enhanced MRA is

performed by using a timed and rapid injection of a gadolinium-based contrast

agent, such as gadolinium dimeglumine[17,18] . Because the volume of contrast

agent is limited to 15-20 mL in most cases, timing of the contrast agent bolus

and good venous access are essential. The images are obtained by using a short

TR, short TE, and T1-weighted technique (TR/TE/flip angle, 4.9/2.4/35°). The

images are displayed in multiple projections by using an MIP technique [19].

Carotid Doppler ultrasonography

Doppler ultrasonography is the primary noninvasive test for evaluating carotid

stenosis.[20,22,23]Primary examination of the carotid plaque is somewhat

subjective, because terms such as soft plaque or irregular surface are often used

to describe the primary ultrasonographic images. The degree of stenosis is

better measured on the basis of the waveform and spectral analysis of the CCA

and its major branches, especially the ICA [21].

8

2.4. Previous studies:

A study done by Ribeiro, R. A. et al[23] at 2006, Forty-six heads from male

embalmed human cadavers were studied and all specimens were fixed in 10%

formaldehyde solution. Anomalous tortuosities, dilatations, aneurisms or

atheromatous/occlusive disease samples were discarded at the beginning of the

study. Abnormal origins of the carotid arteries also were discarded.The arterial

length and diameters were measured as follows: total length of the common

carotid arteries (CCA), external diameter of the CCA at origin level, external

diameter of the CCA at bifurcation level, external diameter of the internal

carotid artery (ICA) and external diameter of external carotid artery (ECA),

both at origin levels.CCA bifurcation level was measured in relation to

clinically relevant anatomical landmarks as follows: superior level of the

thyroid cartilage, mandible angle and ear lobe. The bifurcation level of the CCA

in relation to the cervical vertebra was also investigated. Their study showed

that the superior border of the thyroid cartilage was the most stable anatomical

landmark for predicting the CCA bifurcation level and it is important to

mention that from all the landmarks studied, the cervical vertebra was the only

one to show differences between sides, with the left side bifurcation level more

variable than the right side [23].

There was a case report of a 72-year-old man with bilateral intrathoracic carotid

bifurcations associated with a Klippel-Feil anomaly. The left and right carotid

bifurcations were located at levels corresponding to the second and fourth

thoracic vertebrae, respectively. A possible association between low carotid

bifurcation and the Klippel-Feilanomalywas suggested [24].

9

In a cadaveric study by VatsalaA R et al.[25], the cadavers used for dissection

were availed from the Department of Anatomy, SS Insitute of Medical sciences,

Davangere. Eighty common carotid arteries (40 left, 40 right) were dissected for

the purpose of data collection. High levels of bifurcation were considered to be

above the C 3-4 intervertebral junction, and low bifurcations below it. The

upper border of thyroid cartilage was the anterior landmark for the C 3-4

junction. High or low levels of origin of the right common carotid artery were

defined in relation to the level of the sternoclavicular joint. The study showed

that in 51 (63.8%) cases bifurcations were high among which the most common

levels of bifurcation was at the level of C 3 vertebral body (37.5%). T he most

common low bifurcation was at C 4 vertebra level (3.75%). There were no

statistically significant side-to-side differences in level of bifurcation[25].

Another study by K.Radha[26] was undertaken in 40 adult formalin fixed

cadavers procured from the division of Anatomy, Raja Muthiah Medical

College, Chidambaram and KarpagaVinayaga Medical College,

Madhuranthagam. The dissections were carried out according to the instructions

given in Cunningham’s manual of practical anatomy. The level of bifurcation of

common carotid artery was noted and correlated with the upper border of

thyroid cartilage. If the level of bifurcation was above or below the upper

border of thyroid cartilage, the distance between the upper border of thyroid

cartilage and bifurcation were measured. The results showed that The level of

bifurcation of the common carotid artery was at the level of upper border of

thyroid cartilage in sixty-seven cases .Only nine cases showed the higher level

with the range of 3.2 mm to 19.3 mm above the level of upper border of thyroid

cartilage.4 cases showed the lower level of bifurcation in the range of 2 mm to

10 mm below the level of upper border of thyroid cartilage [26].

10

Chapter Three

MATERIALS & METHODS

10

3. MATERIALS & METHODS:

3.1. The Study design:

Descriptive cross sectional study

3.2. Study area:

Dissection rooms of Khartoum state universities.

3.3. Study population:

Available cadavers in the Dissection rooms of Khartoum state universities.

Inclusion criteria:

All cadavers in the Dissection rooms of Khartoum state universities

with preserved common carotid arteries and their bifurcation.

Exclusion criteria:

Cadavers that were macerated by students before data collection.

3.4 . Samples Size & Techniques:

Total coverage of all cadavers in the Dissection rooms of faculties of medicine

in Khartoum state. The cadavers will be dissected according to the instructions

given in Cunningham’s manual of practical anatomy[27]. The level of bifurcation

of common carotid artery will be noted and correlated with the upper border of

thyroid cartilage. If the level of bifurcation is above(high) or below(low) the

upper border of thyroid cartilage, the distance between the upper border of

thyroid cartilage and bifurcation will be measured.

11

3.5. Study instrument:

Check list (Annex).

3.6. Data analysis

The data will be analyzed by using SSPS16 software.

3.7. Ethical consideration:

Verballyfrom head of the department in each university

12

Chapter Four

RESULTS

12

4. RESULTS:

A 30 cadavers were dissected in both sides, numbered, photographed and the

following results were obtained from 60 cases (30 right and 30 left).

The level of bifurcation were normal (at the level of the upper border of thyroid

cartilage) [photograph 4.1] in 22 cases (36.6%), high (above the level of the

upper border of thyroid cartilage) [photograph 4.2] in 37 cases (61.6%) and low

(below the level of the upper border of thyroid cartilage) [photograph 3] in one

case (1.6 %) as shown in figure 4.1.

Figure 4.1: levels of bifurcation of the common carotid

artery.

13

In 30 cases (50%), the origin of the superior thyroid artery was from the

external carotid artery [photograph 4.3], in 28 cases (46.6%) from bifurcation of

the common carotid artery [photograph 4.4] and in 2 cases (3.3%) from the

common carotid artery[photograph 4.5] as shown in figure 4.2 .

Figure4. 2: Origins of the superior thyroid artery.

14

In the left side, the level of bifurcation was normal in 13 (43.3%) cadavers, high

in 17 cadavers (56.6%) and no low level of bifurcation were observed, while in

the right side, the level of bifurcation was normal in 9 (30%) cadavers, high in

20 cadavers (66.6 %) and low level of bifurcation were observed in one cadaver

only as shown in figure 4.3.

As shown in figure 4.4, in the left side, the origin of the superior thyroid artery

was from the external carotid artery in 9 cadavers (30%), from bifurcation of

the common carotid artery in 20 cadavers (66.6%) and from the common

carotid artery in one cadaver (3.3%).In the right side, the origin of the superior

thyroid artery was from the external carotid artery in 21 cadavers (70%), from

Figure4. 3: levels of bifurcation of the common carotid

artery in the right and left sides.

15

bifurcation of the common carotid artery in 8 cadavers (26.6%) and from the

common carotid artery in one cadaver (3.3%).

(20) 66.6%

(1) 3.3%

(9) 30%

(8) 26.6%

(1) 3.3%

(21) 70 %

Figure 4.4: Origins of the superior thyroid artery in the right and left

sides.

16

TC CCA

TC TC

CCA

Photograph 4.2: low level of bifurcation of

the common carotid artery(CCA); below

the upper border of thyroid cartilage (TC).

Photograph 4.1: normal level of

bifurcation of the common carotid

artery(CCA); at the level of upper border of

thyroid cartilage (TC).

a

TC

CCA

17

Photograph 4.3: high level of bifurcation of the

common carotid artery(CCA); above the upper

border of thyroid cartilage(TC). And origin of

superior thyroid artery (STA) from external

carotid artery (ECA)

ECA

STA

CCA

Photograph 4.4: origin of

superior thyroid artery

(STA) from bifurcation of

the common carotid artery

(CCA).

CCA

STA

18

STA

CCA

Photograph 4.5: origin of superior thyroid artery (STA) from

common carotid artery (CCA).

19

Chapter Five

DISCUSSION

19

5. DISCUSSION

The result of this study showed that the level of bifurcation were normal (at the

level of the upper border of thyroid cartilage) in 22 cases(36.6%), high (above

the level of the upper border of thyroid cartilage) in 37 cases(61.6%) and low

(below the level of the upper border of thyroid cartilage) in one case only (1.6

%).This result is similar to a study done by Vatsala A Ret al.[25], they stated that

in 51 (63.8%) cases bifurcations were high among which the most common

levels of bifurcation was at the level of C 3 vertebral body (37.5%). The most

common low bifurcation was at C 4 vertebra level (3.75%). On the other hand,

it was reported that in a study done by K.Radha[26] showed that the level of

bifurcation of the common carotid artery was at the level of upper border of

thyroid cartilage in 83.7% of cases .Only 11.2% cases showed the higher level

above the level of upper border of thyroid cartilage and 5% of cases showed

the lower level of bifurcation below the level of upper border of thyroid

cartilage. In support of that study done by Lucev et al [28],The level of

bifurcation of common carotid artery was found to be at the upper border of

thyroid cartilage in 50% and the higher level of bifurcation of common carotid

artery was found to be 37.5% and the lower bifurcation of Common was

reported to be 12.5% . another study was given by Gulsen et al they reported

that a case of bilateral low-lying bifurcation of the common carotid artery [29].

The superior thyroid artery typically arises from the anterior surface of the

external carotid artery just below the level of the greater cornu of hyoid bone[30].

Lucev et al. reported that the superior thyroid artery arises more often from the

common carotid artery in 47.5% cases; 16% of cases by Hollinshead[31] and in

10% of cases by Banna and Lasjaunias[32]. In the present study, the origin of the

superior thyroid artery was from the external carotid artery In 30 cases (50%).

20

Vandana et al. reported origin of superior thyroid artery 0.5 cm proximal to

bifurcation of CCA [33].also Pakhiddey reported a case of low origin of that the

superior thyroid artery in our study we reported in one cadaver that the origin of

the superior thyroid artery was from the common carotid artery bilaterally. In an

study by Abhijeet J. et al.[34], the superior thyroid artery was found to be arise

from carotid bifurcation in 31.81% of cases. In present study, in 28 cases

(46.6%) the superior thyroid artery arise from the carotid bifurcation.

Also Ampali M. et al. [35] studied the level of bifurcation in both sides (100 right

and 100 left) and showed that in the right side the normal levels were 44% of

cases, high levels in 54% of cases and low in 2% of cases. In present study, in

the right side, the level of bifurcation was normal in 9 cases (30%), high in 20

cases (66.6 %) and low level of bifurcation were observed in one case only. The

study of Ampali M. in the left side showed that normal levels were in 70 %,

high levels in 30% and no cases of low bifurcation. Our study showed that in

the left side, the level of bifurcation was normal in 13 (43.3%) cadavers; high in

17 cadavers (56.6%) and no low level of bifurcation were observed.

In the present study in relation to the origin of superior thyroid artery ,in the

right side, it was found that from the external carotid artery in 21 cases (70%),

from bifurcation of the common carotid artery in 8 cases (26.6%) and from the

common carotid artery in one case (3.3%) but in the left side, the origin of the

superior thyroid artery was found that from the external carotid artery in 9 cases

(30%), from bifurcation of the common carotid artery in 20 cases (66.6%) and

from the common carotid artery in one case (3.3%) this result is similar to study

of 33 cadavers done by Abhijeet J. et al. which showed that the superior

thyroid artery in the right side arise from the external carotid artery in 60.6% ,

from the bifurcation in 36.3% and from common carotid artery in 3.3% of

21

cases. In the left side it showed that the superior thyroid artery arises from the

external carotid artery in 72.7%, from the bifurcation in 27.2% and no case

from common carotid artery. This study supports the present study.

22

Chapter Six

CONCLUSION & RECOMMENDATIONS

22

6.1. Conclusion:

In conclusion this study showed that the commonest level of bifurcation of

common carotid artery in Sudanese people was found that at higher level. There

was variation in the side of origin of superior thyroid artery between right &left

sides.

6.2. RECOMMENDATIONS:

According to this study we recommend that the surgeons should be aware

that the level of bifurcation of the common carotid artery in Sudanese people

was higher level (above the upper border of thyroid cartilage) followed by

normal level (upper border of thyroid cartilage) then low level (below the

upper border of the thyroid cartilage).

There is a variation in the sites of origin of superior thyroid artery the most

commonly from the external carotid artery followed by bifurcation then

from common carotid artery.

Side variation in origin of the superior thyroid artery should be considered.

Further studies using more sample sizes are needed to confirm the findings

of this study.

23

Chapter Seven

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23

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27

ANNEX

28

The National Ribat University

Faculty of Graduate Studies & Scientific Research

Master degree of clinical and human anatomy

Study check list for a research on:

A Cadaveric Study of the Level of Bifurcation of the Common Carotid

Artery in Sudanese People.

By: FathElrahman Abu Elgasim Ibrahim.

Supervisor: Dr. Muhammed Ahmed Abulnor

1/Cadaver no.

2/Side:

1. Right.

2. Left.

3/Level of the bifurcation:

1. Upper border of thyroid cartilage(C4).

2.High(above the upper border of thyroid cartilage).

3.Low ((below the upper border of thyroid cartilage)

4- Origin of superior thyroid artery:

1. External carotid artery

2. Common carotid artery

3. Bifurcationof common carotid artery