The branching pattern of the middle cerebral artery: is the intermediate trunk real or not? An anatomical study correlating with simple angiography

Laboratory investigation

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The branching structure of the middle cerebral artery (MCA) remains a debated issue. In this study the authors aimed to describe this branching structure in detail.


Twenty-seven fresh, human brains (54 hemispheres) obtained from routine autopsies were used. The cerebral arteries were first filled with colored latex and contrast agent, followed by fixation with formaldehyde. All dissections were done under a microscope. During examination, the trunk structures of the MCA and their relations with cortical branches were demonstrated. Lateral radiographs of the same hemispheres were then obtained and comparisons were made. Angles between the MCA trunks were measured on 3D CT cerebral angiography images in 25 patients (50 hemispheres), and their correlations with the angles obtained in the cadaver brains were evaluated.


A new classification was made in relation to the terminology of the intermediate trunk, which is still a subject of debate. The intermediate trunk was present in 61% of cadavers and originated from a superior trunk in 55% and from an inferior trunk in 45%. Cortical branches supplying the motor cortex (precentral, central, and postcentral arteries) significantly originated from the intermediate trunk, and the diameter of the intermediate trunk significantly increased when it originated from the superior trunk. In measurements of the angles between the superior and intermediate trunks, it was found that the intermediate trunk had significant dominance in supplying the motor cortex as the angle increased. The intermediate trunk was classified into 3 types based on the angle values and the distance to the bifurcation point as Group A (pseudotrifurcation type), Group B (proximal type), and Group C (distal type). Group A trunks were seemingly closer to the trifurcation structure that has been reported on in the literature and was seen in 15%. Group B trunks were the most common type (55%), and Group C trunks were characterized as the farthest from the bifurcation point. Group C trunks also had the smallest diameter and fewest cortical branches. Similarities were found between the angles in cadaver specimens and on 3D CT cerebral angiography images. Beyond the separation point of the MCA, trunk structures always included the superior trunk and inferior trunk, and sometimes the intermediate trunk.


Interrelations of these vascular structures and their influences on the cortical branches originating from them are clinically important. The information presented in this study will ensure reliable diagnostic approaches and safer surgical interventions, particularly with MCA selective angiography.

Article Information

Address correspondence to: Ayhan Comert, M.D., Department of Anatomy, Ankara University, Faculty of Medicine, 06100 Sihhiye, Ankara, Turkey. email:

Please include this information when citing this paper: published online February 24, 2012; DOI: 10.3171/2012.1.JNS111013.

© AANS, except where prohibited by US copyright law.



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    In a left hemisphere with the parenchyma totally excised, the standard branching structure of the MCA is shown. AA = angular artery; AP = anterior parietal artery; AT = anterior temporal artery; CA = central artery; IntT = intermediate trunk; IT = inferior trunk; LSA = lenticulostriate artery; MT = middle temporal artery; OF = orbitofrontal artery; PF = prefrontal artery; PP = posterior parietal artery; PreCA = precentral artery; PT = posterior temporal artery; ST = superior trunk; TA = temporal artery; TO = temporooccipital artery; TP = temporopolar artery.

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    Photograph showing the distribution of the cortical branches coursing through the sylvian fissure in the left hemisphere at the lateral section of the brain.

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    The temporal lobe was dissected at a point 5 cm proximal to the temporal pole to examine the trunk and cortical branches in the left hemisphere. Upper: Photograph showing the brain before dissection. Lower: Photograph showing the trunk structures and cortical arteries.

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    Types of intermediate trunk based on origination points. A: Group A (pseudotrifurcation type) in the right hemisphere. B: Group B (proximal type) in the left hemisphere. C: Group C (distal type) in the left hemisphere. The X denotes the length of the MCA.

  • View in gallery

    Illustrations showing Group A (pseudotrifurcation type) (A), Group B (proximal type) (B), and Group C (distal type) (C) intermediate trunks originating from the superior trunk in a right hemisphere. ACA = anterior cerebral artery.

  • View in gallery

    Inter-trunk angles and relations with cortical branches in a left hemisphere; superolateral wide view (A), lateral narrow view (B), and lateral radiograph (C). In the presence of an intermediate trunk originating from the superior trunk, the cortical branches supplying the motor cortex are thicker and more dominant when the angle between these 2 trunks increases. F = frontal lobe; T = temporal lobe.

  • View in gallery

    Sagittal conventional CT angiogram (left) and 3D CT cerebral angiogram (right) obtained in a 62-year-old female patient suffering from subarachnoid hemorrhage who presented with severe headache. This case can be classified as Group C (distal type). The angles between the MCA trunks and their relations are demonstrated. In this case, the angle between the superior and intermediate trunks is greater than 90°. According to assessments of the present study, cortical branches supplying the motor cortex may have a marked dominance. EB = early branch.



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