Imaging investigations of meningiomas of optic nerve sheath

Abstract

Objective To investigate CT and MR imaging findings of meningiomas of optic nerve sheath, and to evaluate the “tram-track” sign and its clinical significance. Methods CT and MR imaging findings of thirty-five patients with meningiomas of optic nerve sheath confirmed by histopathology were analyzed retrospectively. The age of the patients was from 6 to 71 years (mean age 41.63 years). There were 20 females and 15 males. CT scanning was performed in 28 patients with contrast scanning in 25, and MR imaging was performed in 27 patients with contrast scanning in 25. Results Of the 35 cases with meningiomas of optic nerve sheath, fusiform thickening mass was found on CT and/or MR imaging in (12 cases,) diffuse tubular enlargement mass in 7, ovoid mass in 1, localized eccentric expansion in 8, and large diffuse irregular mass within the orbit in 7. Enlargement of intraorbital segment of the optic nerve was seen in all 35 cases, enlargement of intracanalicular segment simultaneously in 22, enlargement of intracranial segment simultaneously in 13, mass of optic chiasm simultaneously in 4, and enlargement of optic tract simultaneously in 1. CT scanning performed in 28 patients showed iso-density mass in 20 and mass containing calcification in 8. Enhancement of the tumor was observed on post-contrast CT in all 25, and the “tram-track” sign was clearly seen in 6. MR imaging performed in 27 patients displayed hypointense mass on T_1- and T_2-weighted images in 16, isointense mass on T_1- and T_2-weighted images in 8, and long T_1 and long T_2 signal intensity mass in 3. After contrast, marked enhancement of the mass was seen in all (25 cases), and the “tram-track” sign was clearly demonstrated in 17. By way of statistical analysis, MR imaging was superior to CT in demonstrating the “tram-track” sign (P=0.001). Conclusion CT and MR imaging could demonstrate the site, configuration, and characteristics of the tumor. MR imaging was superior to CT in the diagnosis of meningiomas of optic nerve sheath.