Surgical Nuances and Predictors of Requirement for Suprameatal Tubercle Removal in Microvascular Decompression for Trigeminal Neuralgia.

Suprameatal tubercle (SMT), a bony prominence located above the internal acoustic meatus, is reported to impede the microscopic view during microvascular decompression (MVD) for trigeminal neuralgia (TN). For an enlarged SMT, removal of the SMT may be required in addition to the routine MVD to precisely localize the offending vessels. The objective of this study is to investigate the predictive factors influencing the requirement of SMT removal during trigeminal MVD.  We retrospectively reviewed 197 patients who underwent MVD for TN, and analyzed the correlation of the SMT height and other clinicosurgical data with the necessity to remove the SMT during MVD. The parameters evaluated in the statistical analyses included maximum SMT height, patient's clinical characteristics, surgical data including the type and number of offending vessels, and surgical outcomes.  SMT removal was required for 20 patients among a total of enrolled 197 patients. In the univariate analysis, maximum SMT height, patient's age, and number (≥ 2) of offending vessels were associated with the requirement for SMT removal. Multivariate analysis with binary logistic regression revealed that the maximum SMT height and number (≥ 2) of offending vessels were significant factors influencing the necessity for SMT removal. A receiver operating characteristic curve analysis revealed that an SMT height ≥ 4.8 mm was the optimal cutoff value for predicting the need for SMT removal.  Large SMTs and the presence of multiple offending vessels are helpful in predicting the technical difficulty of trigeminal MVD associated with the necessity of SMT removal.