Basilar and distal vertebral artery occlusive disease: correlation of MR imaging and MR angiography

The purpose of this study is to evaluate the correlation of brain lesions seen on magnetic resonance imaging with vascular occlusive disease of the basilar and distal vertebral arteries as documented on MR angiography. The clinical findings are also correlated with the findings on MR imaging and MR angiography. The clinical records of twenty-one patients with proven occlusive disease of the distal vertebral and/or basilar arteries were retrospectively reviewed. All the patients were imaged utilizing either the Siemens Magnetom 1.5 T SP 4000 and the Siemens 1.0 T Impact systems. Dual MR angiographic techniques were employed including two-dimensional (2D) and three-dimensional time-of-flight. The 2D sequences utilized fast low angle shot gradient echo sequences. The 3D sequences utilized fast image steady-state precession gradient echo sequences. Gadolinium contrast was utilized for increased angiographic detail in one patient. Magnetization transfer contrast was used in three patients. The individual partitions as well as the maximum intensity pixel projection images were evaluated in each case. The most extensive brain lesions were seen in the group of patients with severe basilar and/or combined vertebrobasilar disease. One-half of these patients showed non-specific scattered foci of T2 lengthening similar to the findings found in a group of patients with noncritical stenosis. MR imaging invariably demonstrated more lesions than were clinically suspected. Even though the brain lesions tended to be more extensive in patients with severe vascular disease, the amount of brain tissue damage was not an adequate parameter to document the degree of vascular narrowing. The degree of vascular narrowing was useful in therapy planning. Such data was obtained by the MR angiograms, but not by MR imaging. MR angiography is a useful complementary examination when lesions in the basilar and distal vertebral vascular territories are diagnosed on MR imaging. MR angiography can differentiate critical from noncritical stenosis and can thus play a key role in the therapeutic decision making process.