Left C1 schwannoma

Noncontrast CT (A) shows well-circumscribed osteolysis (arrows) of the anterior arch of C1. Pre- (B) and postcontrast (C) T1-weighted MRI shows an enhancing intradural and extramedullary mass (thick arrows) that extends laterally through the left C1 neural foramina. Sagittal postcontrast T1-weighted image (D) shows the extent of enhancing tumor in the neural foramen and paraspinal soft tissues.