Abstract: Objective: To study the morphology of middle cerebral artery (MCA) M1 segment. Methods: We selected the MRA data of 794 MCA (400 of the left side and 394 of the right side) from January 1, 2011 to June 30, 2011 consecutively and analyzed the morphology of the MCA M1 segment in axial, anteroposterior and lateral view, measured the length of the M1 segment, and analyzed the similarity of the left and right side M1 segment morphology. Results: In axial, anteroposterior and lateral view, the MCA M1 segment showed C-shape > L-shape > S-shape. In axial view, it was about 373 (47%) M1 segment performance for the C-shape, of which 340 (42.8%) M1 segments showed bowing to the dorsal side, only 33 (4.2%) M1 segments showed bowing to the ventral side. In anteroposterior view, it was about 322 (40.6%) M1 segments of the performance of the C-shape, of which 262(33.0%) M1 segments showed a bowing to the superior, 60 (7.6%) showed bowing to the inferior. The similarity of the left and right MCA M1 segments was 27.2% (114/419) in axial view and 42.7% (179/419) in anteroposterior view. It was more similar in anteroposterior view than in axial view. Along with the increase of age, in the axial view, L-shape converted to C-shape very obviously, but only mildly elevated in S-shape. In anteroposterior view, the L-shape converted to the C-shape or S-shape along with the increase of age. Conclusion: The different morphology of MCA M1 segment in axial and anteroposterior view may be involved in the development of intracranial atherosclerosis.

Key words: Middle cerebral artery, Anatomy, Magnetic resonance angiography