Objective: To summarize the literature on the electrophysiology of Cavanagh Syndrome (CS), to present a clinical application and to propose an updated electrophysiologic protocol. Methods:A systematic literature search for CS was carried out and a clinical application is presented.Results: CS is characterized by congenital thenar hypoplasia and can be associated with other regional muscular and vascular anomalies. The main electrophysiologic abnormality in patients with CS is a reduced amplitude median compound muscle action potential (CMAP) to the thenar eminence, which is also seen in CTS. Radiographic, and electrodiagnostic findings of a patient with co-morbid CS and CTS is presented. Evaluating the median CMAP to the first lumbrical may assist with the diagnosis of CTS in patients with CS. Conclusions:As CTS and CS can present with thenar atrophy and low amplitude CMAPs, electromyographers should be aware of the clinical and radiographic characteristics of CS and consider electrophysiologic evaluation of the first lumbrical.