Fourth branch of arch of aorta and its clinical implication

In human beings the most common branching pattern of the aortic arch was its division into three great vessels ie the brachiocephalic trunk, left common carotid artery and the subclavian artery. The vertebral arteries arise from the superior aspect of the first part of the subclavian artery. In present case, a left vertebral artery arose from the aortic arch as fourth branch was found. The diameter of left vertebral artery at its origin was 6 mm as compared to the right vertebral artery, which has diameter of 3.5 mm at its origin. In this case left sixth dorsal intersegmental artery might have persisted as first part of vertebral artery hence left vertebral artery arising from arch of aorta. Knowledge of the variations in branching pattern of the aortic arch is important in the diagnosis of intracranial aneurysm after subarachnoid haemorrhage. J. Biomed. Sci. 2015, 2(3):21-23.


ABSTRACT
In human beings the most common branching pattern of the aortic arch was its division into three great vessels ie the brachiocephalic trunk, left common carotid artery and the subclavian artery. The vertebral arteries arise from the superior aspect of the first part of the subclavian artery. In present case, a left vertebral artery arose from the aortic arch as fourth branch was found. The diameter of left vertebral artery at its origin was 6 mm as compared to the right vertebral artery, which has diameter of 3.5 mm at its origin. In this case left sixth dorsal intersegmental artery might have persisted as first part of vertebral artery hence left vertebral artery arising from arch of aorta. Knowledge of the variations in branching pattern of the aortic arch is important in the diagnosis of intracranial aneurysm after subarachnoid haemorrhage.

Introduction:
In human beings the most common branching pattern of the aortic arch was its division into three great vessels ie the brachiocephalic trunk, left common carotid artery and the subclavian artery. This pattern occurs in 65-80% of the cases1. The vertebral arteries arise from the superior aspect of the first part of the subclavian artery. This artery takes a vertical posterior course to enter into the foramen transversarium of sixth cervical vertebra. The segment of the artery from its origin at subclavian artery to its respective foramen transversarium is called the pretransverse or prevertebral segment [1,2]. The variation in origin and course of left vertebral artery and its importance in cerebral disorders clinically and surgically has been described. Its importance in head and neck surgery, angiography and arterial dissection has also been mentioned in the literature [3,4].
In this case report, I am presenting a left vertebral artery as fourth branch of the aortic arch in a 65 year old male cadaver. I am going to discuss embryological, clinical and surgical implications of this artery.

Case Report:
During   likely to occur and make impact in these surgeries. These variations are due to the altered development of certain brachial arch arteries during the embryonic period of gestation 5. If the critical variations of branches of the arch of aorta not recognized at surgery; there may be fatal consequences [6]. Congenital cardiac defects and coronary arterial abnormalities were associated with the angiographic detection of common origin of brachiocephalic trunk and left common carotid artery. When planning the palliative or corrective procedures, and assessing the potential benefit of the surgical repair over the long term; it is necessary to understand the pathophysiological effects of such a defect [7]. Vascular remodeling within the aorta results in a loss of structural integrity with consequent aneurysm formation [8].
Normally the first part of vertebral artery develops from proximal part of dorsal branch of seventh cervical intersegmental artery proximal to postcostal anastomosis. The second part develops from longitudinal communications of the postcostal anastomosis. The proximal parts of intersegmental arteries are exposed to longitudinal tension and bending due to caudal shifting of the aorta resulting in retarded blood flow and abnormal connections between longitudinal channels (vertebral artery) and subclavian artery or aorta [3,9]. In present case, we found left vertebral artery arose from the aortic arch as fourth branch. In this case left sixth dorsal intersegmental artery might have persisted as first part of vertebral artery hence left vertebral artery arising from arch of aorta. Bhattarai C and Poudel PP studied 85 cadavers at Manipal College of Medical Sciences, Pokhara, Nepal over a period of three years. They found variations in 17 cadavers (20 %). Common origin of the brachiocephalic trunk and left common carotid artery was found in 11 cadavers (12.9 %). Direct origin of left vertebral artery from arch of aorta was found in 6 cadavers (7.0 %) 6. Siva Kumar GL et al described case of 55 year old cadaver. In this case, they found an unusual common trunk for brachiocephalic trunk and left common carotid artery. Brachiocephalic trunk was trifurcated into right vertebral artery, right common carotid artery and right subclavian artery. Left vertebral artery was seen to arise from arch of aorta [10]. The anomalous branching pattern of the aortic arch can alter the cerebral haemodynamics, which in turn can lead to cerebral abnormalities. In aortic arch surgeries, these anomalous branches should be detected prior to the surgery. The ligation of the common carotid artery may lead to complications in the posterior cranial fossa blood supply if the vertebral artery originates from the carotid artery or through its branches [10,11].

Conclusion
Knowledge of the variations in branching pattern of the aortic arch is important in the diagnosis of intracranial aneurysm after subarachnoid haemorrhage. Clinicians and surgeons should be aware of aortic arch variations. Early identification of these vascular anomalies through diagnostic interventions is crucial in order to avoid complications during heart and vascular surgeries. Thus we conclude that it is important to be aware of this type variation in the origin and course of left vertebral artery as it might have serious implication in surgical and angiographic procedures.