Lesions Mimicking Small Vestibular Schwannomas

Objective Most tumors of the internal auditory canal and cerebellopontine angle (CPA) are vestibular schwannomas (VSs). Preoperative diagnosis is based on typical clinical symptoms and radiological findings. In rare cases, histopathology can, however, show different results. Design This is a retrospective chart and database review. Setting The study was conducted at a tertiary skull base referral center at a university hospital. Participants A total of 207 consecutive cases of VS surgery via the middle cranial fossa approach performed between December 2005 and January 2015 were reviewed. Main Outcome Measures The main outcome measures were definitive histologic findings in 198 specimens, analysis of preoperative magnetic resonance imaging (MRI) and computed tomography. Results Histopathology revealed three meningiomas and two cases of lipochoristomas. Clinical presentation was typical for VS in all five cases. In preoperative MRI, all tumors were suspected to be VSs. Retrospective analysis of the preoperative imaging did not lead to a modification of the diagnosis. Intraoperative findings showed increased adherence of the tumor to the adjacent tissue in two of the five cases. Conclusion CPA lesions other than VSs are unusual but have to be taken into account. In very small tumors, imaging still remains difficult.