A Preligamentous Variant of the Thenar Motor Branch of the Median Nerve.

We report a rare variant of the thenar motor branch (TMB) of the median nerve. A preligamentous TMB was discovered during revision carpal tunnel release in a 49-year-old man. The prevalence and characteristics of TMB variations are discussed. The literature describing iatrogenic injury to the TMB variants, surgical treatment, and preoperative screening tools is reviewed. Recognition of anatomic variants of the TMB is essential considering notable consequences of iatrogenic injury.