Analysis of magnetic resonance tomographic angiography false negatives in trigeminal neuralgia before microvascular decompression

Objectives The aim of this study was to clarify the reason for the high rate of false-negative cases for offending vessels determined by magnetic resonance tomographic angiography (MRTA) in trigeminal neuralgia (TN) patients before microvascular decompression (MVD). Methods Preoperative MRTA imaging was performed in 115 patients with TN. The characteristics of the offending vessels were determined by MRTA prior to MVD. The relationships between TN and surrounding vessels were classified into two types, MRTA-positive (contact or compressing) and MRTA-negative (near or distant), and compared with the surgical findings. Results According to the surgical findings in the 100 MRTA-positive patients, vascular compression was found in 90 patients, vascular contact without compression was found in six patients, and no contact between vessels and the root of TN was found in three patients. Bony compression was found in one patient. In the 15 MRTA-negative patients, small artery compression (one with arterial wall stiffening) was found in seven patients, venous compression was found in two patients, arachnoid thickening and adhesion were found in three patients, and no vessel compression was found in three patients. MRTA showed sensitivity of 91.4 % (96/105) and specificity of 60 % (6/10). Conclusions Preoperative MRTA is valuable for determining the offending vessels in TN patients. However, owing to its inability to distinguish offending vessels such as small arteries, small veins, and vessels with wall calcification in addition to abnormal blood flow, the false-negative rate is comparably high.