Inflammatory Pseudotumor of the Trigeminal Nerve: A Neoplastic Mimic You Do Not Want to Miss

A 24-year-old woman with left-sided headache and facial numbness. A, Unenhanced axial CT scan in a bone algorithm shows remodeling and destruction of bone at the left base of skull (arrows). Also note mild sclerosis of the left clivus (asterisk). B, Unenhanced axial CT scan in a bone algorithm shows marked expansion of the left foramen ovale (asterisk) and expansion of the left foramen rotundum (R). C, Axial fast spin-echo T2-weighted MR image demonstrates the mass in the foramen rotundum (R), along the course of the left fifth nerve including Meckel cave (arrow) and along the nerve in the prepontine cistern (asterisk). Note the normal right Meckel cave (M). D, Enhanced axial T1-weighted MR image shows the avidly enhancing soft-tissue mass along the left fifth nerve involving Meckel cave and the cisternal portion of the trigeminal nerve. E, Enhanced coronal T1-weighted MR image shows the mass involving the infratemporal fossa (IT) and foramen ovale (asterisk) along the fifth nerve to Meckel cave and the intracranial compartment. Note the normal right Meckel cave (M). F and G, Postoperative axial (F) and coronal (G) enhanced T1-weighted images obtained 8 weeks following surgery while the patient was on steroid therapy show marked interval reduction in the abnormal soft tissue within the left infratemporal fossa and along the fifth cranial nerve extending to the intracranial compartment.