Bupivacaine injection to lateral rectus in abducens nerve palsy

A 49-year-old female presented with bilateral abducens nerve palsies. She had 75 prism diopter esotropia. The extraocular movement of the lateral rectus was -1 limitation for the right eye and -4 limitations for the left. After performing orbital magnetic resonance imaging (MRI), 2 mL of bupivacain (5 mg/mL) was injected into the left lateral rectus (LR). One month after injection, a further orbital MRI was performed. Subsequently, recession of both medial rectus (6 mm) and resection of the left LR (9 mm) were performed. After one month, bupivacaine had no hypertrophic effects. There was little change in angle of deviation. The orbital MRI scan showed a 1.91% increase in volume compared to the muscle prior to the injection. Histological findings showed no muscle fibers of the left LR muscle, only the fiber nucleus and the collagen that replaced the fibers. We report on the changes in stiffness and muscle volume and on the histology of the muscle one month after injecting bupivacaine into the paralyzed left LR muscle combined with standard surgical treatment.