Sensitivity and specificity of MRA in the diagnosis of neurovascular compression in patients with trigeminal neuralgia

The published rates of operatively confirmed neurovascular compression as the cause for trigeminal neuralgia range from 10 % to nearly 100 %. High-definition magnetic resonance angiography (MRA) was performed in 27 consecutive patients (in 6 cases with 3D reconstructions) to show neurovascular compression preoperatively. The MRA findings were compared with the relationship between the Vth nerve and the surrounding vessels at surgery. In 23 patients MRA showed present neurovascular compression in accordance with surgical findings (18/27 in complete accordance of type and side of vessel, site and direction of compression). One woman had no neurovascular compression either on MRA or intraoperatively. One MRA prediction of neurovascular compression was false, and two results were false negative. The sensitivity of MRA was therefore 88.5 % but the specificity only 50 %, if surgical findings are the reference. In one patient with right trigeminal neuralgia MRA revealed bilateral neurovascular compression of the Vth nerves. Therefore, the overall specificity of MRA might be below 50 %. In one patient with multiple sclerosis, the decision to operate was markedly influenced by the clear finding of neurovascular compression on MRA. The patient has been free from trigeminal pain for 149 weeks after microvascular decompression. In 6 patients, 3D reconstructions of the MRA data were performed. The images helped in 3D visualisation of the operation, but did not yield new information about the nature of the vessels revealed, or the site, direction or side of the neurovascular compression. Received: 15 May 1997 Accepted: 18 June 1997