The MCA divides approximately 10 to 12 mm from its origin. The postbifurcation trunks fo the M1 segment follow a nearly parallel course, diverging only minimally prior to reaching the MCA genu.
In the majority of cases, the MCA divides proximal to the genu.
The main MCA trunk is variable:
Source : Diagnostic Cerebral Angiography - Anne G. Osborn