Imaging description

Mediastinal peripheral nerve sheath tumors (schwannoma and neurofibroma) almost always present as a paraspinal soft tissue mass in the posterior mediastinum. They have sharply defined margins and are round or lobulated in shape. Peripheral nerve sheath tumors generally follow the horizontal axis of the nerve. In 50% of cases, they apply pressure to adjacent bony structures leading to widening of the neural foramen or erosion of an adjacent rib or vertebral body (Figures 34.1 and 34.2) [1]. Ten percent extend through the adjacent intervertebral foramen into the spinal canal and form an “hourglass” or “dumbbell” shape (Figure 34.1) [1]. The mass has homogeneous or heterogeneous enhancement with intravenous contrast (Figure 34.1) [1, 2]. Punctate calcification is seen in 10% of schwannomas [3]. MRI findings include low to intermediate signal intensity on T1- and intermediate to high signal intensity on T2-weighted sequences (Figure 34.3) [4]. There is tumor enhancement with intravenous gadolinium (Figures 34.1 and 34.2).