[A Case of Bilateral Trigeminal Neuralgia and the Possible Onset Mechanisms Based on the Operative Findings].

Several cases of bilateral trigeminal neuralgia(TN)have been reported;however, the possible onset mechanism has rarely been discussed. We encountered a case of bilateral TN occurring in two stages. A 64-year-old woman presented with left TN. Magnetic resonance imaging showed the transverse pontine vein adhering to the left trigeminal root and superior cerebellar artery adhering to the right trigeminal root;however, no symptoms were noted. Immediately after microvascular decompression(MVD)on the left side, TN disappeared completely. However, 2 years postoperatively, the patient presented with right TN. The second MVD surgery revealed that the right cerebellar surface severely adhered to the dura mater, particularly under the surface of the tentorium. The arachnoid membrane at the cerebellopontine angle was slightly adhered. The patient was completely free from pain after the second MVD. The intraoperative findings suggested that the brain stem may have shifted and the cerebellopontine cistern may have narrowed because of cerebellar adhesion to the surrounding structures and arachnoid adhesion. We speculate that such structural changes in the posterior fossa after the first operation may have caused the asymptomatic vascular adhesion to change into the symptomatic offending adhesion over time.