[Predictive value of MRI for detecting and characterizing vascular compression in cranial nerve hyperactivity syndromes (trigeminal and facial nerves)].

MRI detects vascular compression of the cranial nerve in the majority of the cases. High-resolution 3D-T1 and 3D-T2 MRI gives detailed images, particularly the 3D-T2 MRI sequences, with good contrast between cerebrospinal fluid and vascular and nerve structures. TOF-AMR (native sequence and vertebrobasilar reconstruction) shows the vascular structures in hypersignal and therefore differentiates the vessels from the cranial nerves. The 3D-T1 sequence with gadolinium reinforces the signal of the venous structures. Thus, preoperative MRI makes it possible to predict the existence of a vascular compression. The correlation study between imaging data and intraoperaitive anatomical findings showed a sensitivity of MRI of 97% and a specificity of 100%. In addition, it can specify the type and the degree of the compression. This information may help in selecting the most appropriate surgical method.