Detection of middle cerebral artery stenosis using 3D-CTA and MRA

The usefulness of magnetic resonance angiography (MRA) and three-dimensional computed tomography angiography (3D-CTA) for detecting middle cerebral artery (MCA) stenosis was evaluated by comparison with digital subtraction angiography (DSA) in 37 patients with 40 stenotic lesions of the MCA. The maximum intensity projection (MIP) of 3D-CTA was also performed for 25 of the 40 lesions. MRA showed the same degree of stenosis as DSA in 6 of the 40 lesions (15%) and overestimated stenosis in 34 (85%). 3D-CTA demonstrated the same degree of stenosis in 19 of the 40 lesions (48%), overestimated stenosis in 19, and underestimated stenosis in 2. The MIP of 3D-CTA showed the same degree of stenosis in 21 of the 25 lesions (84%), overestimated stenosis in 3, and underestimated stenosis in 1. Different degree of stenosis were found on the anteroposterior and axial projections in 2 of the 40 lesions on MRA, 7 of the 40 lesions on 3D-CTA, and 10 of the 25 lesions on the MIP of 3D-CTA. MIP may solve the difficulty in investigating the degree of stenosis of MCA using the axial projection of DSA. MRA should be performed first to screen for stenotic lesions because of less invasiveness, absence of complications due to contrast medium, no radiation damage, and fewer false negative findings. Uncertain cases should be examined using the MIP of 3D-CTA to achieve the correct diagnosis. This combination of screening tests prevents the performance of unnecessary angiography, and provides a less invasive and correct identification of craniocervical vascular lesions in older patients in whom angiography is difficult to perform. (author)