Background: Carpal tunnel syndrome (CTS) is well-known. Less familiar are proximal median nerve entrapments such as the lacertus syndrome. Lacertus syndrome symptoms are very similar to CTS, but often unknowledged.
Case description: A 37 year old male with persistent tingling of the median nerve area after 3 CTS releases on both wrists. The diagnosis CTS was confirmed with EMG and ultrasound. In our outpatient clinic we saw weakness of the tip pinch (FPL, FDP2). Loss of sensibility in the proximal thenar and digits 1-3 and a positive scratch collapse test. We suspected the patient has lacertus syndrome and performed a lacertus release. All symptoms dissolved afterwards.
Conclusion: If symptoms do not resolve after CTS-release proximal median nerve compressions should be considered. Tip pinch strength and sensibility of the thenar can differentiate between the various locations of median nerve entrapment. Redo CTS-release lead to unnecessary treatment and costs, because of the wrong diagnosis.