Background: There exits some similarity between symptoms of carpal tunnel syndrome (CTS) and myofascial pain related to trigger points (TPs) in the infraspinatus muscle.
Aim: The aim was to examine what proportion of patients referred with a clinical suspicion of CTS had myofascial pain in the infraspinatus muscles and how their occurrence was related to the outcome of nerve conduction studies (NCS).
Methods: We examined the occurrence of CTS and of TPs in infraspinatus muscles in a cohort of patients suspected for CTS and referred to the Department of Clinical Neurophysiology, Aarhus University Hospital from October 2003 to February 2004. Patients underwent electrodiagnostic studies of the median and ulnar nerves. Additional tests were performed if necessary. Patients were examined for TPs by a blinded examiner immediately after NCS.
Results: We included 335 patients (202 females; 133 males, mean age 46). Two hundred one patients (60%) had abnormal NCS indicating CTS. Fifteen patients (4%) had other electrodiagnostic abnormalities. One hundred nineteen patients (36%) had normal NCS. Forty nine percent (58 out of 119) of the subjects with normal NCS had TPs in the infraspinatus muscles whereas only 26% (53 out of 201) of the patients with abnormal NCS indicating CTS had TPs. Likewise, 26% (4 out of 15) of the patients with other electrodiagnostic abnormalities had TPs.
Conclusions: Approximately one third of patients referred with a clinical suspicion of CTS had TPs in the infraspinatus muscles. This occurrence was higher in the group with normal NCS than in the group with abnormal NCS indicating CTS. When CTS is suspected clinically, physicians must be aware of TPs in the infraspinatus muscles as a possible cause of the symptoms; thus, NCS are important in these patients.