Suprameatal Tubercle: Its Implication in Microvascular Decompression for Trigeminal Neuralgia

초록

Purpose: The suprameatal tubercle (SMT) is a prominence in the superior lip of the porus of the internal acoustic meatus Large SMT blocks access to the trigeminal nerve and the prepontine cistern medial to the trigeminal nerve and the prepontine cistern medial to the trigeminal nerve. Meterial and Method: We evaluated the degree of prominence of the SMT on preoperative MRI and CT and the extent of hindrance by SMT during operation in 57 patients with trigeminal neuralgia (TN) who underwent microvascular decompression (MVD) Result: Of 57 MVD for TN, there were 2 cases with large SMT enough to cause difficulty in evaluating the offending site and mobilizing the offending vessel. The cause of TN was lateral compression by petrosal vein in one patient and medial compression by superior cerebellar artery in the other patent. SMT was so large that access to the offending site was difficult and undue retraction of trigeminal nerve was necessary to mobilize the offending vessel and place Teflon felt in both patients. Transient sensory hypoesthesia in V2 dermatome developed in one patient due to excessive manipulation of trigeminal nerve. Conclusion: Large SMT can cause trouble in MVD for TN. Its presence should be evaluated on preoperative MRI and/or CT. In case of large SMT, we can select one of two options depending on situation’ to manipulate trigeminal nerve more than usual taking risks of trigeminal nerve injury or to drill off the SMT to minimize manipulation of trigeminal nerve.