Etiologic exploration of magnetic resonance tomographic angiography negative trigeminal neuralgia.

Our objective was to explore the etiologic factors involved in trigeminal neuralgia with negative magnetic resonance tomographic angiography (MRTA) results. Clinical data from 341 patients with idiopathic trigeminal neuralgia who were treated with neurovascular decompression between March 2003 and December 2011 were retrospectively analyzed. The etiologic causes of preoperative MRTA-negative trigeminal neuralgia were categorized based on comparisons between preoperative MRTA and intraoperative endoscopic images. MRTA was highly sensitive (92.4%, 291/315) to neurovascular compression, whereas its specificity was 65.4% (17/26). Among the 24 false-negative cases, there were nine patients with petrosal vein compression, 12 with superior cerebellar artery compression, two with superior cerebellar arterial branch compression, and one patient with anterior inferior cerebellar artery compression. Among the 17 true-negative cases, three patients had arachnoid adhesions, one had a protruding temporal eminence, five had micro-cholesteatomas, and eight patients exhibited no compression. The factors responsible for the MRTA-negative results included small-diameter arterial vessels, veins with slow blood flow, arachnoid adhesions, protruding temporal eminences, micro-cholesteatomas, and other pathologies such as multiple sclerosis. Preoperative diagnoses of MRTA-negative patients need to integrate the MRI results from multiple sequences to discriminate between arteriolar compression, venous compression, and small compressive lesions. When narrow cerebellopontine angles are shown in MRTA, arachnoid adhesion and temporal eminence compression should be considered.