DEMONSTRATION OF NEUROVASCULAR COMPRESSION IN TRIGEMINAL NEURALGIA WITH MAGNETIC-RESONANCE-IMAGING - COMPARISON WITH SURGICAL FINDINGS IN 52 CONSECUTIVE OPERATIVE CASES

Until recently, the inability to demonstrate neurovascular compression of the trigeminal nerve preoperatively resulted in surgery being offe red only in cases of severe trigeminal neuralgia (TGN), frequently aft er a prolonged trial of medical treatment and following less invasive procedures, despite the fact that posterior fossa microvascular decomp ression gives long-term pain relief in 80% to 90% of cases. To assess whether vascular compression of the nerve could be demonstrated preope ratively, high definition magnetic resonance tomographic angiography ( MRTA) was performed in 50 consecutive patients, five of whom had bilat eral TGN, prior to posterior fossa surgery. The imaging results were c ompared with the operative findings in all patients, including two pat ients who underwent bilateral exploration. Vascular compression of the trigeminal nerve was identified in 42 of 45 patients with unilateral symptoms and on both sides in four patients with bilateral TGN. In the last patient with bilateral TGN, neurovascular compression was identi fied on one side, and on the other side the compressing superior cereb ellar artery was separated from the nerve by a sponge placed during pr evious surgery. There was full agreement regarding the presence or abs ence of neurovascular compression demonstrated by MRTA in 50 of 52 exp lorations, but MRTA misclassified four vessels compressing the trigemi nal nerve as arteries rather than veins. In two cases, there was disag reement between the surgical and MRTA findings. In the first of these cases, surgery revealed distortion of the nerve at the pens by a vein that MRTA had predicted to lie 6 mm remote from this point. In the sec ond patient. venous compression was missed; however, this patient was investigated early in the series and did not have gadolinium-enhanced imaging. In nine cases, MRTA correctly identified neurovascular compre ssion of the trigeminal nerve by two arteries. Moreover, MRTA successf ully guided surgical reexploration in one patient in whom a compressin g vessel was missed during earlier surgery and also prompted explorati on of the posterior fossa in two patients with multiple sclerosis and one patient with Charcot-Marie-Tooth syndrome, in whom neurovascular c ompression was identified preoperatively. It is concluded that MRTA is an extremely sensitive and specific method for demonstrating vascular compression in TGN. As a result, open surgical procedures can be reco mmended with confidence, and microvascular decompression is now the tr eatment of choice for TGN at the authors' unit. They propose MRTA as t he definitive investigation in such patients in whom surgery is contem plated.