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ORIGINAL ARTICLE
Year : 2013  |  Volume : 61  |  Issue : 2  |  Page : 117--121

Microsurgical anatomy of the anterior cerebral artery in Indian cadavers

Shweta Kedia1, Sahni Daisy2, Kanchan Kumar Mukherjee1, Pravin Salunke1, Rakshith Srinivasa1, Mathuriya Suresh Narain1,  
1 Department of Neurosurgery, Post Graduate Institute of Medical Education and Research, Chandigarh, India
2 Department of Anatomy, Post Graduate Institute of Medical Education and Research, Chandigarh, India

Correspondence Address:
Kanchan Kumar Mukherjee
Department of Neurosurgery, PGIMER, Chandigarh - 160 012
India

Abstract

Background: The microanatomy features of cerebral arteries may be variable and may be different in different ethnic groups. Aim: To study the anterior cerebral artery (ACA) anatomy in North-West Indian cadavers. Materials and Methods: Microanatomy features of the ACA were studied in 15 formalin fixed human cadaveric brains under microscope. The outer diameter, length, and number of perforating branches with respective anomalies were measured for each of the following vessels: ACA (proximal A1 segment to distal A2 segment), anterior communicating artery (ACoA), Recurrent artery of Heubner (RAH), and callosomarginal artery and photographed for documentation. Results: The mean length and external diameter of right and left A1 segment was 12.09 mm and 12.0 mm and 2.32 mm and 2.36 mm respectively. Narrowing, duplication, and median ACA were seen in 6.6%, 3.3% and 6.6% of the vessels respectively. Complex ACoA type was seen in 40% cadavers. RAH originated at an average point of 0.2 mm distal to ACoA, but in one cadaver it arose 5 mm proximal to ACoA. Double RAH was found in 26.6%. The course of RAH in relation to A1 was superiorly in 60%, in anteriorly 30% and posteriorly in 10% of cadavers. The orbitofrontal artery (OFA) and frontopolar artery (FPA) arose from A2 in 83.3% to 40% respectively. The mean distance of OFA and FPA from ACoA was 4.17 mm and 8.5 mm respectively. After giving rise to central, callosal and cortical branches, pericallosal artery terminated near the splenium of the corpus callosum or on the precuneus as the inferomedial parietal artery. Conclusion: Knowledge of the microvascular anatomy is indispensable and it is mandatory to be aware of the possible variations in the anomalies to minimize morbidity.



How to cite this article:
Kedia S, Daisy S, Mukherjee KK, Salunke P, Srinivasa R, Narain MS. Microsurgical anatomy of the anterior cerebral artery in Indian cadavers.Neurol India 2013;61:117-121


How to cite this URL:
Kedia S, Daisy S, Mukherjee KK, Salunke P, Srinivasa R, Narain MS. Microsurgical anatomy of the anterior cerebral artery in Indian cadavers. Neurol India [serial online] 2013 [cited 2020 Oct 27 ];61:117-121
Available from: https://www.neurologyindia.com/text.asp?2013/61/2/117/111113


Full Text

 Introduction



Anterior cerebral artery (ACA) is an often encountered structure in common neurosurgical cases, and it is important for a surgeon to be well versed with the demographically prevalent variations in its anatomy. We analyzed the structural variations in ACA anatomy in North-West Indian regions.

 Materials and Methods



Fifteen formalin fixed adult cadaveric human brains were studied from the internal carotid artery bifurcation, proximal ACA, to distal anterior cerebral artery (DACA) with their branches.

 Results



Details of A1 segment of ACA are given in [Table 1]. Disproportionately developed A1 segment: Diameter, length, and number of perforators are shown in [Table 2]. Some of the anomalies observed in A1 anatomy are shown in [Figure 1] and [Figure 2]. A1 segment perforators: All, but one perforator arose from the posterosuperior surface of A1, one perforator from the inferior surface in the proximal part, and none from the anterior.{Figure 1}{Figure 2}{Table 1}{Table 2}

Anterior communicating artery (ACoA) was above the chiasma in all the cadavers, was horizontal in 2 and oblique in 13 specimens. Length of ACoA was between 3 mm and 4 mm and diameter varied between 1 mm and 2 mm. One or both ACoA of a duplicate or fenestrated ACoA were equal to or larger than the smaller A1 segment in 40% of the brains examined. There was no correlation between the difference in size of the right and left A1 segments, and the size of the ACoA was found. The ACoA diameter was 1.8 mm when the difference in diameter between the right and left A1 segments was 0.5 mm or less; it was 1.6 mm if the difference was greater than 0.5 mm. The ACoA had fenestration in 1 and duplication in 5 and rudimentary in 1 and was normal in remainder. Better formed duplication of the ACoA gave origin to a perforator in one and third A2 in other. ACoA perforators were 3-5 in number, with 0.1-0.8 mm diameter. Arising from the posterosuperior surface of the ACoA they coursed superiorly to the optic chiasm and suprachiasmatic area. In 50% of brains with unequal A1s, they arose ipsilateral to the dominant A1 and in 80% of brains with equal A1s they arose from the central portion of ACoA.

Recurrent artery of Heubner (RAH) arose from A2 to ACoA junction in 12, A1-ACoA junction in 2 and A1 segment in 1 cadaver. It arose as a common origin with the medial orbitofrontal branch in one from A1 [Figure 3]. The point of origin was between 5 mm proximally in one cadaver to 0.3 mm distal to ACoA and was symmetrical in 80% cadavers. Two separate RAH, or a common branch giving rise to two RAH were present in eight hemispheres, five on the right and three on the left. Three RAH were present in one hemisphere. In all instances of doubling, the vessel caliber was similar. [Table 3] gives the details of RAH anatomy three types of course of this vessel were observed. The type I or superior course was seen in 60%. The type II or anterior course was seen in 30%. The type III or posterior course was seen in 10% arteries.{Figure 3}{Table 3}

DACA segment, the horizontal segment coursed predominantly in the sulcus of the corpus callosum, in 90% of hemispheres and 10% ran above it medial to the cingulate gyrus. The A2 diameter (pre-callosomarginal) ranged from 1.5 mm to 3 mm. Both the A2 were of equal diameter in 12. In one case, third A2 was seen to arise from the posterosuperior surface of the ACoA [Figure 4]. One case had a bihemispheric A2 [Figure 5], the right pericallosal artery ended in the cingulate sulcus just beyond the level of the genu of the corpus callosum.{Figure 4}{Figure 5}

Callosomarginal artery (CMA) was in the sulcus above the cingulate gyrus and followed a course roughly parallel to that of the pericallosal artery in 80% of cadavers. The size of the pericallosal artery distal to the CMA varied inversely with the size of the CMA. Immediately past the origin of CMA, the pericallosal and CMA were equal in diameter in 33.3% of cases; the pericallosal was larger in 40%, and the CMA was larger in 22.7%. The origin varied from first distal to ACom to genu.

Of the cortical branches, the smallest cortical branch was the orbitofrontal artery (OFA) and the largest was the posterior internal frontal artery. The frontopolar artery (FPA) and orbitofrontal were the most consistent vessels, and the least frequent branch the inferior parietal (13.3%). Of the major cortical branches, internal frontal and paracentral artery arose most frequently from the CMA. The cortical branch that arose most frequently from the CMA was the middle internal frontal artery. Of the CMA present, 43.3% gave origin to 2 major cortical branches 43.3% gave three, and 6.6% gave four branches. The origin, its frequency, and diameter are described in [Table 4]. The OFA originated 4-8 mm and FPA about 4-15 mm distal to ACoA. Inferior parietal artery was the least frequent branch [Table 4].{Table 4}

Subcortical branches-callosal branches: The corpus callosum was most commonly supplied by the perforating branches (short callosal arteries). These branches were present in 80% of hemispheres and numbered from 10 to 12. In 6.6% of cadavers, well-formed longer branches (long callosal artery) arose from pericallosal artery and coursed parallel to pericallosal artery. DACA terminated inferior to the most vertical portion of the splenium of the corpus callosum in 20% hemispheres.

 Discussion



Normal course of the ACA has been well described. [1] Fischer, subdivided ACA into five segments. [2] An Indian study by Pai et al. [3] on A1-ACom and DACA observed that the variations were more common in the distal segments. However, they have not studied DACA beyond the origin of CMA. The variation in length and diameter of A1 was similar to that described by Perlmutter and Rhoton. [4] In our study 33.3% of A1 segments were symmetrical. The shorter A1 segments were stretched tightly over the chiasm; the longer ones passed anteriorly over the optic nerves. Hypoplastic A1 (<1.5 mm) was seen in 6.6% in our study and 10% in the study by Perlmutter and Rhotons. [4] Both duplication and aplasia of A1 has been described. [4],[5],[6] In this study, only one duplication was noted and the average number, length of perforators and site of origin (more laterally) were similar to observations in the other studies. [4],[7] These observations suggest that during surgery, the temporary clip should be placed as medially as possible to avoid perforator ischemia.

Similar to reported observations literature, RAH originated from proximal A2, A1-A2 junction as a single trunk with OFA. [8],[9] Multiple (double, triple or quadruple) RAH have been described unilaterally or bilaterally to arise as common trunks or separate origins, [10],[11] and these were associated with other vascular variations or malformations. Symmetrical origin of RAH varied from 30 to 80% in various studies. [8],[9],[10],[11] The diameter of the artery and length (due to multiple loops) varies highly, and similar results were observed in this study. [8],[9],[12] Owing to multiple loops, the length of the RAH varied significantly, [13] we found the length of RAH to vary from 16 mm to 28 mm. RAH in relation to the A1 trunk had superior course, anterior course or posterior course. [10],[11] Occlusion or iatrogenic damage of this vessel, close to A1 segment at its origin, causes a mediobasal striatum infarct leading to symptoms such as faciobrachial hemiparesis and aphasia on the dominant hemisphere. [8],[11] with emotional and motivational symptoms. [4],[12]

In this study, a normal ACoA connecting two A1 segments of equal diameter was observed in 33.3% of cases while it was 41.5% in other study [14] The average length of ACoA in this study was 3.3 mm (3-4 mm) compared to 2.6 mm to other studies. [4] Anomalous ACoA was observed to be 40% as compared to 59% in other study. [13] The number and diameter of the perforator observed in this study were similar to those reported in other studies. [15],[16] Perforators arose mostly from the superior and posterior aspect and rarely from the anterior or inferior surfaces. The origin of perforators had no proximity with dominant A1 unlike that described in the literature. OFA and the FPA could be identified in all the hemispheres similar to the observation in the other studies. However, we observed the origin of FPA from A3 unlike the observations by others, in those studies it arose from A2. [17],[18]

Hemispheres with typical CMAs (23.3%) had relatively longer course of the CMA entering the cingulate sulcus, running parallel to the pericallosal with no significant differences between the diameters of the two. The internal frontal arteries are the most variable branches of the distal ACA and arise from the A3 segment of the pericallosal or CMA. [19] In five hemispheres, they arose in groups of two from the other cortical branches or individually from the A2 segment. The cortical branches arose from the pericallosal more frequently than they did from the CMA. With the exception of the internal frontal especially, MIF and paracentral arteries arose most frequently from the CMA. When the area supplied by the paracentral artery as well as its origin and course are considered, it would not be wrong to describe it as the most regular branch of the distal ACA with the least number of variations. In the absence of CMA [Figure 6], all cortical branches (similar diameter) arose from the peri callosal at a right angle, at almost identical distance directly reached the cortex they supplied and were observed in two (6.6%) of the hemispheres in this study akin to those described by Moscow et al. [19] FPA and AIFA arose in these hemispheres from a location proximal to the CMA in a single or thick trunk. If no regression occurs during the embryological development, the posterior pericallosal artery courses around the splenium as a posterosuperior choroidal artery (7% in the 3 series).{Figure 6}

The frequency of occurrence of the "azygos pericallosal artery" or ACA azygos varies from 0 to 5%. [20],[21] In this study, no cadaver had this patter. If only one of the two A2 segments is underdeveloped, its territory may be vascularized either by the median artery of the corpus callosum or the contralateral pericallosal artery. We did not observe the former variation in any of our series. The latter variation corresponds to the bihemispheric pericallosal artery (4-13.3%), [15],[22] We did observe a bihemispheric DACA.

This study and review of the literature suggest that neurosurgeons should be aware of the microanatomy and variations of the distal ACA so that confident surgical and endovascular interventions can be performed.

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