Insular branch resembling lenticulostriate artery from M2 inferior trunk of middle cerebral artery: cadaver anatomic study.

Whether the lenticulostriate artery (LSA) can branch from the M2 inferior trunk of the middle cerebral artery (MCA) remains unclear. However, although rare, some branches from the M2 inferior trunk have been observed to run along the LSA from the MCA M1 segment or M2 superior trunk. In addition, these branches could be clinical problems by running across the MCA bifurcation. Therefore, we investigated whether these branches were truly LSAs using cadaveric heads, and assessed their clinical significance. We examined 32 hemispheres of 16 cadaveric heads using microscopy to evaluate the branches from the M2 inferior trunk and their relationships with other arteries, including the M1 segment, M2 branches, and LSAs. Among the 32 hemispheres, four exhibited branches from the M2 inferior trunk running along the LSA. However, these branches terminated at the limen insulae and did not run in the Sylvian cistern and did not reach the anterior perforated substance. Therefore, they were not truly LSAs. We defined these branches from the M2 inferior trunk as "insular branches from the M2 inferior trunk resembling LSA". In some clinical cases, such as "MCA bifurcation aneurysm" and "insular glioma", these branches could be surgical problems by running across the MCA bifurcation. Moreover, in these four hemispheres, the LSAs were observed to branch from the M2 superior trunk. Although this variation is infrequent, awareness of this variation would be useful for the safer operations, particularly in cases that the LSAs branch from the M2 superior trunk.