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 Table of Contents  
ORIGINAL ARTICLE
Year : 2022  |  Volume : 11  |  Issue : 4  |  Page : 194-203

Anatomical variations of anterior cerebral artery and its cortical branches through 1.5 tesla magnetic resonance angiography


1 PG Resident, Department of Anatomy, Government Doon Medical College, Dehradun, Uttarakhand, India
2 Assistant Professor, Department of Anatomy, Government Doon Medical College, Dehradun, Uttarakhand, India
3 Associate Professor, Department of Anatomy, Government Doon Medical College, Dehradun, Uttarakhand, India
4 Tutor, Department of Anatomy, Government Doon Medical College, Dehradun, Uttarakhand, India
5 Statistician, Department of Community Medicine, Government Doon Medical College, Dehradun, Uttarakhand, India
6 Professor and Head, Department of Anatomy, Government Doon Medical College, Dehradun, Uttarakhand, India

Date of Submission22-Sep-2022
Date of Decision03-Oct-2022
Date of Acceptance06-Oct-2022
Date of Web Publication29-Oct-2022

Correspondence Address:
Jolly Agarwal
Department of Anatomy, Government Doon Medical College and Associated Hospitals, Dehradun, Uttarakhand
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/NJCA.NJCA_165_22

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  Abstract 


Background: Cortical branches of the anterior cerebral artery (ACA) supply the medial surface and superior border of the cerebral hemisphere. Names of distinct cortical branches are according to the regions of the brain supplied by that particular branch. There can be variations in the number, origin, and distribution of these branches. There can also be variations of the ACA like azygous, bi hemispheric, median, aplasia, and fenestration of the ACA. This study aimed to evaluate the anatomical variation of the ACA and its cortical branches taking into consideration their number and site of origin. Methodology: Retrospective cross-sectional analysis of magnetic resonance angigraphs of 80 subjects (42 males and 38 females) without cerebrovascular diseases who was undertaken in the department of radiodiagnosis from July 2021 to August 2022. Results: The cortical branches were seen either being completely absent or present singly or in duplication. The callosomarginal artery (CmA) branch was found to be most commonly absent (51.25% on the right side), paracentral lobule artery most commonly duplicated (10% of cases on the right). CmA gave origin to the maximum number of cortical branches as compared to other cortical branches. The abnormal origin of anterior cortical branches was found to be more than posterior cortical branches. A few rare cases of variations (1.25% cases each) like azygous, bihemispheric, aplastic, and median ACA. Conclusion: In the present study different variations were observed in the cortical branches of ACA. These variations may also result in higher incidence of ischemic stroke in territory of ACA, involving the superior medial part of the parietal lobe and midline of the frontal lobe. Therefore, this study can be of clinical importance to neurosurgeons during cerebral surgeries.

Keywords: Anterior cerebral artery, cortical branches, magnetic resonance angiography


How to cite this article:
Sharma D, Nautiyal A, Saxena S, Saran A, Agarwal J, Kumar P, Maurya RK, Maheshwari S, Pant MK. Anatomical variations of anterior cerebral artery and its cortical branches through 1.5 tesla magnetic resonance angiography. Natl J Clin Anat 2022;11:194-203

How to cite this URL:
Sharma D, Nautiyal A, Saxena S, Saran A, Agarwal J, Kumar P, Maurya RK, Maheshwari S, Pant MK. Anatomical variations of anterior cerebral artery and its cortical branches through 1.5 tesla magnetic resonance angiography. Natl J Clin Anat [serial online] 2022 [cited 2023 Feb 6];11:194-203. Available from: http://www.njca.info/text.asp?2022/11/4/194/359879




  Introduction Top


The internal carotid artery (ICA) has two terminal branches: The middle cerebral artery (MCA) and the anterior cerebral artery (ACA). ACA is the smaller terminal branch of ICA. It starts from the medial end of the stem of the lateral fissure and passes anteromedially to the longitudinal fissure above the optic nerve. Here, it communicates with ACA of the opposite side by a short and transverse anterior communicating artery (AComA). Both ACAs of opposite side course together in longitudinal fissure to pass around genu of corpus callosum (CC) and finally anastomose at its posterior end with posterior cerebral artery (PCA).[1] The distribution of ACA extends to the superior border of the cerebral hemisphere where it meets the MCA supplied area. Its territory includes motor and sensory control of the contralateral lower limb and perineum (i.e., micturition and defecation centers).[2]

Fischer (1938) divided ACA into five segments: A 1 (from termination of ICA to junction of AComA with ACA), A2 segment (proximally from AComA to the genu of CC distally), A3 segment (curved path around genu of CC), A4 segment (from the end of genu to splenial part of CC in callosal sulcus), A5 segment (from the end of A4 segment to termination of ACA)[3] [Figure 1]b.
Figure 1: Cortical branches of the anterior cerebral artery are seen arising from PrCA in (a) MRA brain image and (b) schematic representation. The presence of CmA and cortical branches arising from it can be seen in (c) MRA brain image and (d) schematic representation. MRA: Magnetic resonance angiography, PrCA: Pericallosal artery, CmA: Callosomarginal artery

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From principal cerebral arteries, i.e., ACA, MCA, and PCA two types of branches arise which form two distinct systems, they are central and cortical systems.[4] The cortical branches of ACA comprise the orbital, frontal, and parietal branches. The medial orbital gyrus, gyrus rectus, olfactory bulb, and olfactory tract are supplied by the orbital branch. The branch from the frontal branch supplies the paracentral lobule, medial frontal gyrus, CC, and cingulate gyrus. The parietal branch supplies the precuneus area. Names of distinct cortical branches are according to regions of the brain supplied by that particular branch, e.g., orbitofrontal (OFA), frontopolar (FPA), callosomarginal artery (CmA), anterior internal frontal (AIFA), middle internal frontal (MIFA), posterior internal frontal (PIFA), paracentral lobe artery (PLA), superior internal parietal (SIPA), inferior internal parietal artery (IIPA).[5] In this study, we have studied variations in the number and origin of these cortical branches.

Intracranial arterial variations are a frequent finding in the general population. Knowledge of these vascular variations has a significant clinical impact because some of them predispose patients to the development of an aneurysm or cerebrovascular ischemia. Variations of ACA can be either incidental findings detected during radiological investigation for diseases unrelated to cerebral circulation or can present with aneurysm formation, and ischemic and hemorrhagic manifestations. There can also be variations of ACA like azygous ACA, bihemispheric ACA, median ACA, persistent primitive olfactory artery, aplasia, and fenestration of ACA.[6] Insufficiency in territory of ACA due to these variations can lead to ACA strokes involving the superior medial part of the parietal lobe and midline of the frontal lobe. Such strokes are seen in 0.3%–4.4% cases reported so far.[7]

This study is designed to determine variation in ACA also by magnetic resonance angiography (MRA) brain which is a safe and non-invasive technique for the patient. It will help in establishing anatomical correlation of clinical findings in patients with cerebrovascular insufficiency. In MRA, an angiogram is obtained by selectively detecting flowing protons by two methods either by the time of flight (TOF) method which is the gradient echo technique or another method is phase contrast method which employs phase encoding in three directions.[8] To date, few studies have been reported for cortical branches of ACA regarding its variation in its presence, number, origin, and differences between the right and left side of the MRA brain, particularly in the north Indian population.


  Materials and Methods Top


This study was a retrospective cross-sectional study done in the Department of Anatomy and Radiodiagnosis, from July 2021 to August 2022. Magnetic resonance brain angiographies were done using a 1.5 T magnetic resonance imaging (MRI) machine with model name “uMR580” for all patients who underwent MRA in Department of Radiodiagnosis. Patients with cerebrovascular diseases were excluded from the study. A total of 80 MRI films (42 males and 38 females) were considered for this study. Ethical clearance was obtained for the study from Institutional Ethical Committee with reference number “GDMC/IEC/2022/07.”

The TOF technique was used to take MRA images of the patients.[9] Number, site of origin, and variations of cortical branches of ACA on right and left sides were seen by processing images using maximum intensity projection and volume rendering algorithm [Figure 2].[10] Variations of ACA as a whole which were visualized during the study were also noted and interpreted. Central branches of ACA and RAH were not visualized in 1.5 T MR. Categorical data were presented by frequency and percentage. A statistical test was applied after checking the normality of the data. All data were extended in MS-Excel and processed and analyzed.
Figure 2: showing right ACA (yellow line) and left ACA (green line) in MIP and VR image in MRA brain. ACA: Anterior cerebral artery, MRA: magnetic resonance angiography, MIP: Maximum intensity projection, VR: Volume rendering

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  Results Top


The present study revealed the following facts [Table 1]:
Table 1: Result table

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Presence and duplication of cortical branches of anterior cerebral artery

The cortical branches were seen either being completely absent or present singly or in duplication. CmA branch was found to be most commonly absent (51.25% on the right side and 42.5% on the left side). The second artery commonly absent was IIPA (25% on right and 45% on the left side) followed by SIPA (3.75%on the right and 25%on the left, respectively) [Table 1] and [Graph 1]. PLA on the right side was found to be most commonly duplicated (in 10% of cases). Rest all the cortical branches of ACA were found to be duplicated in the range of 1%–3% except FPA and IIPA on the right side and CmA on both sides in which no duplication was found [Table 1] and [Graph 2].



Origin of cortical branches of anterior cerebral artery from different segments of anterior cerebral artery

Cortical branches that originate from the A1 segment included OFA (6.25% cases), FPA (1.28% cases), and CmA (2.56% cases) on the right side. OFA (72.5% on the right side and 87.55% on the left side) and FPA (64.10% on the right side and 49.38% on the left side) mostly originated from the A2 segment. A few cases of CmA, AIFA, and MIFA, PLA were also reported to originate from the A2 segment.However, none of the cases of PIFA, SIPA, and IIPA arose from the A2 segment. CmA and AIFA were found to be originating from the A3 segment in about half of the cases. However, none of the cases of IIPA originated from the A3 segment. PLA (27.58% on right and 35% on the left side) and SIPA (34.61% on right and 26.23% on the left side) most commonly originated from the A4 segment. IIPA (73.33% on right and 86.66% on the left side) and SIPA (46.15% on right and 59.01% on the left side) most commonly originated from the A5 segment of ACA. However, uncommon origins of all cortical branches from different segments of ACA were also noted [Figure 1]a and [Figure 1]b.

Origin of cortical branches from other cortical branches of anterior cerebral artery

CmA gave origin to the maximum number of cortical branches as compared to other cortical branches of ACA [Figure 1]c and [Figure 1]d and [Figure 2]. AIFA (17.72% on right and 38.67% on left side) and PLA (33.33% on right and 28.75% on left side) most commonly originated from CmA. One case of FPA (1.28%) and one case of MIFA (1.28%) on the right side originated from CmA on the opposite side. FPA gave origin to OFA in 11.25% on the right side and 3.75% on the left side respectively. IFA gave origin to AIFA (8.86% on right and 9.33% on left side), MIFA (16.66% on right and 11.69% on left side) and PIFA (14.49% on right and 10.53% on left side), respectively. Very few cases with the abnormal origin of posterior cortical branches like PLA, SIPA, and IIPA from other cortical branches were also reported.

Anomalies and variations of anterior cerebral artery

Variations of the distal ACA were also found. Azygous ACA was found in one subject (1.25%) of a 45-year-old female in which azygous ACA was formed by the fusion of two A2 segments and run in the medial surface of the hemisphere and divided below the genu to supply both hemispheres (type 2).[9] One case of median ACA was seen in a 64-year-old female in which a third ACA was seen arising from AComA[9] [Figure 3]a. A single case of the bihemispheric ACA was reported in a 53-year-old female in which one A2 segment terminates early and the contralateral artery divides to supply both hemispheres[10] [Figure 3]b. One case of absent (aplasia) of the A1 segment of the ACA artery was also reported in a 66-year-old male[11] [Figure 3]c. Apart from the above one case of fenestration of ACA in 69 years old male was also reported in which the lumen of the artery is divided by the small slit-like fenestration at the junction of the A1 and A2 segment of ACA [Figure 3]d.
Figure 3: Showing variations of anterior cerebral artery (a) Median ACA (b) Bihemispheric ACA (c) Aplasia of right A1segment of ACA (d) Fenestration at A1-A2 junction of right ACA. ACA: Anterior cerebral artery

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  Discussion Top


Presence and duplication of cortical branches of anterior cerebral artery

The prevalence of most of the cortical branches of ACA in the present study was found to be similar to previous studies.[5],[12],[13],[14],[15],[16],[17],[18] However, in the present study, CmA was present in 48.75% of cases on the right side and in 57.50% of cases on the left side, while Cilliers and Page[19] found that the prevalence of CmA was 12.4%. In the present study, PLA was found to be most commonly duplicated (in 10% of cases on the right side) which is endorsed by previous studies[13],[14],[15],[19],[20] [Table 2].
Table 2: Discussion table with variation in number and origin of cortical branches of anterior cerebral artery

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Origin of cortical branches of anterior cerebral artery from different segments of anterior cerebral artery

In the case of OFA cortical branch data for its origin from the A2 segment of ACA approximate with the various quoted studies and for the origin of FPA from A2 Segment, our present study is closely related to Kakou et al. and Cilliers and Page study.[19],[15] Origin of CmA from A2, A3, and A4 segment is found to be by following per under the Cilliers and Page, Cavalcanti et al. and Perlmutter and Rhoton studies,[14],[16],[19] however, it has a significant difference from that of Kawashima et al. study. Few Cases of Posterior cortical branches like PLA, SIPA, and IIPA were reported to be originated from A4 and A5 segments in various studies including our present study, but unlike Cilliers and Page study none of the cortical branch SIPA originated from A2 segment and IIPA from A3 segment.[6] This can be accounted for by the difference in the modality used in Cilliers and Page (cadaveric study) with that of our present study which is based on MR angiography [Table 2].

Origin of cortical branches from other cortical branches of anterior cerebral artery

As in previous studies by Perlmutter and Rhoton,[14] Stefani et al.[5] and Najera et al.,[18] OFA took origin most commonly from FPA, while in our study, it additionally originated from CmA (2.5%), AIFA (2.5%). CmA has not originated from any other cortical branches in the present study as well as in all previously quoted studies in [Table 2]. FPA was found to be originating from OFA in 50% of cases in Najera et al. study, while in our study, we had not found any origin of FPA from OFA.[18] Unlike the previous study mentioned in [Table 2], origin of PLA was found to be additionally from MIFA in the current study. Origin of posterior cortical branches of SIPA and IIPA from CMA, PLA, and CMA, SIPA branches, respectively, was found to be in unison with the previous study [Table 2].

Anomalies and variations of anterior cerebral artery

In the present study, 1.25% cases of azygous ACA were found, which is closely related to studies of Avci et al.,[21] Dunker and Harris,[22] Ugur et al.,[13] Uchino et al.[23] and Stefani et al.[5] in which azygous ACA was found in the range of 0.1%–11.6% cases. In our study, median ACA was found to be in 1.25% of cases which approximates the findings of Uchino et al. study (around 3%) through MRA and almost matches the findings of Kovač et al. study through CTA (1.9%).[24] Bihemispheric ACA was found in 1.25% of cases in the present study which is close to the finding of Kovač et al. while it is not by following per under Perlmutter and Rhoton study (2%–7%) and Cilliers and Page study (20%).[14],[19] A single case of aplasia of the A1 segment of ACA was found in our study which approximates the findings of Dimmick and Faulder study (1%–2%), however, does not correspond to Cilliers and Page (0%) and Kovač et al. study (0.4%).[6],[11],[24] According to the literature prevalence of fenestration of A1 segment was found to be 0.058% in angiographic studies by Dimmick and Faulder and two cases of fenestrated A2 segment were found in Uchino et al. study while we found a single case of fenestration at A1-A2 junction of ACA.[11],[23]


  Conclusion Top


Variations of ACA can be either incidental findings detected during radiological investigation for diseases unrelated to cerebral circulation or can present with aneurysm formation and ischemic and hemorrhagic manifestations. In the present study, different variations of cortical branches of ACA were observed. These variations have their implications during neurosurgery and the treatment of cerebrovascular diseases. Any variation in ACA and its cortical branches can lead to symptoms including loss of motor or sensory control of contralateral lower limb and perineum (i.e., micturition and defecation centers) These variations may also result in the higher incidence of ischemic stroke in the territory of ACA, involving the superior medial part of the parietal lobe and midline of the frontal lobe. Therefore, this study can be of clinical importance to neurosurgeons during cerebral surgeries.

Acknowledgment

The authors sincerely thank Dr. Dibya Prakash Tiwari (Assistant Professor), Department of Neurosurgery, Government Doon Medical College, Dehradun, Uttarakhand for sharing his clinical experiences with cases of neurological diseases. The authors also acknowledge Dr. Avantika Ramola (Senior Resident), Department of Radiodiagnosis, Government Doon Medical College, Dehradun, Uttarakhand for giving her expert opinion on the interpretation of MRA films taken for this study. All subjects who underwent MRA for this study are also acknowledged by the authors.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
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[PUBMED]  [Full text]  
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    Figures

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