Figure 5. Fascicular torsion of median nerve motor fascicles as rare cause of anterior interosseous nerve syndrome.

Monofocal T2 lesion on high-resolution magnetic resonance (MR) neurography of patient 1 guided targeted surgical epineurotomy of the median nerve trunk at upper arm level. The fascicular lesion focus (MR neurography fascicular T2 lesion) was at 9.2 cm proximal to the humeroradial joint space (left, red circle). Surgical exploration precisely at this level revealed subtle increase in median nerve trunk caliber before dissection of its epineurium (before epineurotomy, middle). Fascicular torsion of the anterior interosseous fascicles within the median nerve trunk was found after epineurotomy (asterisk, right). This constriction was carefully mobilized so that eventual detorsion could be performed, followed by satisfactory clinical recovery. Intraoperative images provided by Dr. Thomas Dombert, Dossenheim-Heidelberg, Germany.