Magnetic resonance imaging contribution for diagnosing symptomatic neurovascular contact in classical trigeminal neuralgia: a blinded case-control study and meta-analysis

Although classical trigeminal neuralgia (CTN) is frequently caused by neurovascular contact (NVC) at the trigeminal root entry zone (REZ), both anatomical and MRI studies have shown that NVC of the trigeminal nerve frequently occurs in individuals without CTN. To assess the accuracy of MRI in distinguishing symptomatic from asymptomatic trigeminal NVC, we submitted to high-definition MRI the series of CTN patients referred to our outpatient service between June 2011 and January 2013 (n=24), and a similar number of age-matched healthy controls. Two neuroradiologists, blinded to the clinical data, evaluated whether the trigeminal nerve displayed NVC in the REZ or non-REZ, whether it was dislocated by the vessel or displayed atrophy at the contact site, and whether the offending vessel was an artery or a vein. Our data were meta-analyzed with those of all similar studies published from January 1970 to June 2013. In our sample, REZ contact, nerve dislocation and nerve atrophy were independently associated with CTN (P=.027; P=.005; P=.035 respectively). Compared to a rather low sensitivity of each of these items (alone or in combination), their specificity was high. When REZ contact and nerve atrophy coexisted, both specificity and positive predictive value rose to 100%. Meta-analysis showed that REZ NVC was detected in 76% of symptomatic and 17% of asymptomatic nerves (P<.0001), whereas anatomical changes were detected in 52% of symptomatic and 9% of asymptomatic nerves (P<.0001). In conclusion, trigeminal REZ NVC, as detected by MRI, is highly likely to be symptomatic when it is associated with anatomical nerve changes.