|Year : 2014 | Volume
| Issue : 3 | Page : 166-168
Foetal type posterior cerebral artery -A case report
Manju Bala1, Subhash Kaushal2, Dinesh Kumar Passi3
1 Associate Professor of Anatomy, Medical College, MMU, Mullana, Ambala, Haryana, India
2 Ex - Professor & Head, Department of Anatomy, Govt. Medical College, Patiala, Punjab, India
3 Medical Officer, Department of Surgery, Civil Hospital, Samana, Dist. Patiala, Punjab, India
|Date of Web Publication||21-Jan-2020|
H.No-257, Maharaja Yadvindra Enclave, Patiala, Punjab
Source of Support: None, Conflict of Interest: None
Posterior cerebral artery (PCA),terminal branch of basilar artery join the posterior communicating artery to complete the circle of Willis. The morphological variations of posterior segment of the circle of Willis are much of importance in the diagnosis & treatment of different cerebrovascular diseases.In a series of anatomical dissections of the cerebral arterial territory in 30 cadaveric brain specimens,an important variation of the precommunicating segment of the posterior cerebral artery PI was found. In this variation, an embryonic derivation of the posterior cerebral artery from the internal carotid artery (ICA) known as foetal type posterior cerebral artery was seen. This type of variation may lead to the appearance and severity of syndromes of vascular insufficiency in adults.
Keywords: Posterior cerebral artery, Circle of Willis, Internal carotid artery
|How to cite this article:|
Bala M, Kaushal S, Passi DK. Foetal type posterior cerebral artery -A case report. Natl J Clin Anat 2014;3:166-8
| Introduction|| |
A considerable part of brain is supplied by the branches of two vertebral and two internal carotid arteries. A significant anastomosis, the circulus arteriosus, exists between the vertebral and carotid arterial system. Each posterior cerebral artery is subdivided anatomically into four segment i:e PI toP4. PI segment extends from its origin from basilar artery upto posterior communicating artery. P2 segment extends from its junction with posterior communicating artery to its major branch- the lateral posterior choroidal artery whereas P3 andP4 are distal segments of posterior cerebral artery. The term fetal-type PCA is used when there is still a communication with the basilar artery through a hypoplastic PI segment of the PCA and the knowledge of this kind of variation is important in different vascular surgeries of brain.
| Case Report|| |
During series dissection of brain at Govt, medical college Patiala one of the important variation in PI segment of posterior cerebral artery was seen i.e. foetal type posterior cerebral artery in which size of PI segment of posterior cerebral artery was smaller than posterior communicating artery (PCoA). In this case, PI segment of posterior cerebral artery on right side was hypoplastic and major stem of posterior cerebral artery seemed to arise from internal carotid artery, whereas basilar artery continued as posterior cerebral artery on left side as shown in [Figure 1].
|Figure 1: Showing foetal type PCA|
Abbreviations : P1(R) - Hypoplastic Segment (Foetal type); ICA(R) - Internal Carotid Artery (Right); PCOA - Posterior Communicating artery (Right); BA - Basilar Artery; SCA(L) - Superior Cerebellar artery (Left); PCA - Posterior Cerebral artery.
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| Discussion|| |
The present case report is important and it adds to our knowledge concerning the degree of variability of the arterial supply of major area of cerebral cortex i.e. visual area that lies in occipital lobe of cerebral hemisphere. The knowledge of variations is essential for understanding of severity of syndrome of vascular insufficiency in adults. The present variation i.e. hypoplastic PI segment or foetal type of PI segment is seen on right side. In this variation, the size of PI segment was smaller than that of the size of posterior communicating artery. The major stem of posterior cerebral artery was seen to be arising from internal carotid artery. On the left side basilar artery continued as left posterior cerebral artery with normal PI segment. A large number of authors have described the variability in percentages of abnormalities or hypoplasias in healthy subjects: 15%, 30% and 10.6%,,.
A brief review of the embryogenesis of the cerebral circulation may be helpful to understand this important variation.
At the 4 to 5.7mm stage of the embryo (28-30 days), the ICA, which develops as a cranial extension of the paired dorsal aorta, is formed. Paired longitudinal neural arteries appear along the hindbrain and coalesce to form the basilar artery at the 5- to 8-mm stage. The caudal divisions of the ICA anastomose with the neural arteries and become PCoAs. At the 40-mm stage (8 weeks) the PCAs are an extension of the PCoA. The vertebrobasilar system develops and thus participates in the supply of the PCA through the segment between the basilar artery and the postcommunicating part of the PCA, the PI segment. In that phase, the component vessels of the circle of Willis all have the same caliber. In the remaining fetal period, the circle develops into one of three variants: an adult configuration, a transitional configuration or a fetal (embryonic) configuration. In the adult configuration, the PI segment has a larger diameter than the PCoA. In the transitional configuration, the PCoA and PI have an equal diameter. Both the basilar artery and the ICA thus contribute equally to the PCA. The fetal or embryonic configuration is the variant in which the PI is smaller than the PCoA and the ICAs are the main blood suppliers to the occipital lobes. It has been shown that these variations in morphology arise during fetal brain development. In this period, the frequency of adult and fetal configurations increases, while the number of transitional configurations decreases.
The presence of anomalous origin of PCA from ICA may assume considerable significance if one has to ligate Internal carotid, common carotid or in case of obstruction of these arteries by embolus. In such cases the blood supply of large area of brain might be interrupted. If both cerebral arteries take origin in a normal fashion from the terminal portion of the basilar artery and thrombosis occurs, then infarction will involve both occipital lobes, however if one artery takes origin in this manner and the other PCA arises from carotid then infarction will be confined to a single occipital lobe. It is clear that the site of origin of posterior cerebral artery will often determine both the frequency and the type of visual symptoms noted by patients suffering from carotid and basilar artery disease.
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