S63 Etiology of clinically established trigeminal neuralgia: Role of MRI

Abstract

Objectives Neurovascular compression (NVC) is the commonest cause of trigeminal neuralgia (TN). The use of MRI for diagnosis and presurgical assessment is problematic, because NVC is commonly reported in asymptomatic subjects or affecting asymptomatic nerves TN patients. We reviewed the literature to evaluate the role of MRI in the diagnostics of TN. Methods Medline and Scopus were searched to identify papers on 3-D reconstruction MRI in unoperated patients with unilateral TN. Only papers with 20 patients or more with typical TN were included. Assessment had to be done by two independent radiologists blinded to the side of the pain and the clinical status of the subjects. Results 10 publications fulfilled the criteria. Neurovascular compression/contact was judged to affect 332/385 (86%) of symptomatic and 216/477 (45%) of asymptomatic nerves. Nerve atrophy was assessed in 6 studies (201 symptomatic and 275 asymptomatic nerves in total) showing consistent reduction of volume (12–24%) and cross sectional area (12–18%) in the symptomatic nerve ( p 0.01 ).Based on 7 studies, severe compression (indentation, nerve displacement) was significantly more common in symptomatic than asymptomatic nerves ( P 0.05 ). Discussion The high prevalence of ‘innocuous’ NVC of asymptomatic nerves is confirmed. NVC is more likely to be the cause of TN when nerve atrophy is present and/or the compression is severe (and is at the root entry zone). No exact cutoff values can yet be presented however. Conclusion NVC is clinically relevant for TN only if associated with evidence of anatomical changes in the symptomatic nerve. Significance The role of MRI in assessment of patient with TN clarified.