Anatomical Variations in the Circulus Arteriosus Cerebri with Clinical Importance - Results of an Magnetic Resonance Angiography Study and Review of Literature

Abstract

Objectives: Anatomy of circulus arteriosus cerebri (CAC) shows wide variation in different individuals, and population groups and has vital clinical significance in causation and presentation of clinical disease. The literature revealed a connection between the variations of CAC and cerebrovascular disease, ischemia, stroke, aneurysms, and atherosclerosis.

Material and methods: In this study, 513 patients without clinical manifestation in regard to cerebrovascular diseases, who are considered healthy on CAC anatomy, are included. Patients were instructed by clinicians for head imagery with magnetic resonance angiography examination during 2016-2017 periods.

Results: After statistical analysis, 43.27% were male while 56.72% female, 39% were younger than 40 years old. Age interval lies from 11 to 84 years old, mean age 46. The most common variations or 9.74% is when communicant anterior artery absence and absence of both posterior communicant arteries (Type G*/E) more rarely is H*/G (0.2%), G*/D (1.75%), G*/G (0.6%), H*/D (0.4%), H*/E (3.39%), H*/H (0.4%), J*/E (0.6%), while combination J*/D, J*/G, J*/H, G*/H not found. The most often combination is absence of anterior communicant artery and absence of both posterior communicant artery (Type G*/E), more in male 10.36% than female 9.6%.

Conclusion: The CAC is considered to play a critical role in preventing future stroke events in patients with absent of any of the arteries. Knowledge on variations in arteries forming the CAC is with clinical significance, as it is one of the components of CAC which stabilizes cerebral blood flow when principle conduits fail. Knowing the structure of arteries provide clinical knowledge to the surgeons before planning neurovascular surgeries.

Keywords: Cerebral artery; Circulus arteriosus cerebri; Clinical importance; Interventional of cerebral artery; Variations of circulus arteriosus cerebri.

Figure 1:

Schematic view of anatomic variations of anterior and posterior part. (G*) Hypoplasia or absence of an anterior communication. (H*) One pre-communicating segment of an anterior cerebral artery-A1 (ACA) is hypoplastic or absent, the other pre-communicating segment gives rise to both post-communicating segments of the ACAs. (J*) Hypoplasia or absence of an anterior communication. (D) Unilateral PComA present. (E) Hypoplasia or absence of both posterior communicating artery (PComA) and isolation of the anterior and posterior parts of the circle at this level. (G) Unilateral fetal-type posterior cerebral artery and hypoplasia or absence of the contralateral PComA. (H) Unilateral fetal-type posterior cerebral artery and hypoplasia or absence of both pre-communicating segments of the posterior cerebral artery and the PComA.

Figure 2:

Type G* – (a and b) show absence of anterior communicating artery of anterior part of circulus arteriosus cerebri (blue arrows).

Figure 3:

Type H* – (a-d) show absence of anterior cerebral artery-A1 of anterior part of circlus arteriosus cerebri (blue arrows).

Figure 4:

Type D – absence of posterior communicating artery of one side while the other side of posterior part of circulus arteriosus cerebri (blue arrows).

Figure 5:

Type E – (a-c) show absence of both sides posterior communicating artery of posterior part of circulus arteriosus cerebri (blue arrows).

Figure 6:

Type H – (a-d) show P1 absence of the same side accompanied by posterior communicating artery absence of the opposite side or variation absence of posterior part of circulus arteriosus cerebri (blue arrows).