25-year-old male with history of neurofibromatosis type I status post excision of right upper arm lesion. A vitamin E marker was placed on the medial skin surface of the arm approximately 10 cm above the elbow joint. There is band-like low signal intensity and foci of signal void in the underlying soft tissues indicating scarring and metallic susceptibility artifact from prior surgery at this site. An enhancing nerve sheath tumor along the ulnar nerve just above the medial epicondyle seen on the prior study has been intervally resected.There is enlargement of the ulnar nerve along its course associated with multiple nerve sheath tumors. The enlarged ulnar nerve is perched upon the posterior margin of the medial epicondyle, which may reflect interval release. In the area of the surgical resection, there is now an elongated subcutaneous mass that is inseparable from the ulnar nerve. This particular mass measures approximately 2.5 x 1.5 cm in transverse dimension and 4.5 cm in craniocaudal dimension. The mass is mostly isointense to skeletal muscle on T1-weighted images, but heterogeneous on T2-weighted images with areas of both low and high signal intensity. There is minimal enhancement of this mass after gadolinium administration. Nerve sheath tumors are also noted along the courses of the medial and radial nerves with additional innumerable cutaneous, subcutaneous, and intramuscular nerve sheath tumors.Bone marrow signal intensity is normal.
1. Innumerable nerve sheath tumors compatible with stated diagnosis of neurofibromatosis type I.2. Postsurgical changes of a nerve sheath tumor resection along the course of the ulnar nerve above the medial epicondyle of the distal humerus.3. New mass in the area of the resection that is inseparable from the enlarged ulnar nerve. Its signal characteristics are atypical for a nerve sheath tumor with relatively low signal intensity on T2-weighted images suggesting the possibility of a postsurgical neuroma.