Intratumoral microhemorrhages on T2*-weighted gradient-echo imaging helps differentiate vestibular schwannoma from meningioma

BACKGROUND AND PURPOSE: Vestibular schwannomas (VS) may be difficult to differentiate from cerebellopontine angle (CPA) meningiomas. Demonstration of microhemorrhages in VS on T2*-weighted gradient-echo (GRE) sequences may have potential value to differentiate VS from CPA meningiomas.Materials and METHODS: In this prospective study of 20 patients, MR imaging was performed with T2*-weighted GRE in addition to all basic sequences. Histopathologic examination was performed after surgery. Intratumoral hemosiderin was confirmed by pigment staining.RESULTS: There were 15 patients in the VS group with 16 VS and 5 in the meningioma group with 5 posterior fossa meningiomas. Fourteen of the 16 VS and all 5 meningiomas were treated surgically and were confirmed on histopathologic examination. T2*-weighted GRE identified microhemorrhages on T2*-weighted sequence in 15 (93.75%) of the 16 VS. CT excluded calcification in all VS. T2-weighted turbo spin-echo (TSE) and fluid-attenuated inversion recovery (FLAIR) images recognized microhemorrhages in 2 cases. Pigment staining confirmed hemosiderin in all 14 surgically treated VS, and none of the meningiomas showed microhemorrhages on MR imaging. For the detection of microhemorrhages, T2*-weighted GRE showed a sensitivity of 93.8%, specificity of 100%, positive predictive value of 100%, and negative predictive value of 83.3%. The sensitivity of T2 TSE and FLAIR for microhemorrhage was 12.5%. The Fisher exact test showed a statistically significant difference in the differentiation of VS from meningioma on the basis of detection of microhemorrhages (P < .01).CONCLUSION: Most VS demonstrate microhemorrhages on T2*-weighted GRE. This finding is useful to differentiate VS from CPA meningiomas. T2*-weighted GRE should be used as a basic sequence to evaluate CPA tumors. Identification of microhemorrhages may have the potential to assess the aggressive biologic behavior of VS.

Vestibular schwannomas (VS) and meningiomas comprise most cerebellopontine angle (CPA) tumors. VS constitute 80% to 90% and meningiomas 10% to 15% of CPA tumors.¹ It is essential to distinguish these 2 lesions accurately before surgery because the outcome with preservation of hearing is better with meningiomas.¹ MR imaging is considered the imaging method of choice to assess CPA tumors and to distinguish VS from meningiomas. A tumor in the internal auditory canal (IAC) with dilation of the canal is highly suggestive of VS. Signs such as the presence of hyperostosis, calcification, broad base of the tumor against the tentorium, and a dural tail may favor the diagnosis of a meningioma.² However, both VS and meningioma may show similar imaging features, and hence it is not surprising that approximately 25% of CPA meningiomas are mistaken for VS.³ Identification of microhemorrhages may be of interest to assess its relationship to the development of cystic changes in VS and to identify cases at risk of developing clinically significant intratumoral bleed. To our knowledge, no previous study has been done with T2*-weighted gradient-echo (GRE) sequence to assess the presence of intratumoral microhemorrhages and its diagnostic potential in identifying VS.