Acute median nerve compression at the distal forearm caused by a thrombosed aneurysm of an epineural vessel: case report.

The case of a patient with a 2-day history of symptoms suggesting acute carpal tunnel syndrome is presented. However, an urgent electroneurographic examination revealed median nerve compression at the forearm and magnetic resonance imaging confirmed compression by a mass proximal to the carpal tunnel. Surgical exploration showed a recently thrombosed aneurysm of an epineural vessel. Histological and, later, general and angiological investigations could not reveal the underlying cause of this aneurysm. Preoperative electrodiagnostic examination is recommended in acute peripheral nerve compression to prevent decompression at an incorrect site. If atypical nerve compression is suspected, magnetic resonance imaging may be indicated to detect localized nerve compression and its underlying cause.