Example of evoked potential monitoring for a neurogenic tumor positioned high in the mediastinum.

Excision of a neurogenic tumor of the brachial plexus positioned high in the mediastinal space could potentially result in a functional disorder of the arm. We report on a case in which we performed evoked potential monitoring on a tumor located high in the mediastinum. We found large potential changes in the median and ulnar nerve areas and had a concern that the excision might injure the brachial plexus. We did a biopsy and intraoperative rapid histological diagnosis, which promptly revealed that the tumor was not malignant. Thus, we decided not to excise the tumor because the procedure could possibly injure nerves in the arm.