T34. Diagnosing patients with carpal tunnel syndrome: Do you need needle EMG?

Abstract

Introduction Carpal tunnel syndrome (CTS) is a common diagnosis that requires a thorough clinical history and examination. Electrodiagnostic (EDX) evaluation with nerve conduction studies (NCS) is frequently performed to assist the ordering physician when considering additional therapies or surgical intervention. It is a sensitive tool to examine median nerve dysfunction and aids in distinguishing CTS from cervical radiculopathy (CR) by identifying selective slowing of the conduction of median nerve fibers across the carpal tunnel. Some argue that if the NCS shows evidence of CTS, then needle EMG is not necessary. Current practice guidelines consider needle EMG to be an optional test better suited to exclude concurrent causes (cervical radiculopathy) of the patient’s symptoms for improving diagnostic sensitivity. We set out to determine the number of suspected CTS patients with evidence of CTS on NCS who also have concurrent needle EMG evidence of cervical radiculopathy. We aimed to further explore whether clinical examination performed by physicians ordering EDX could distinguish between the diagnoses of CTS and CR before testing is performed. Methods A retrospective chart review of 606 cases of CTS and CR in the Mayo Clinic Arizona EMG Laboratory from January 2015 to January 2016 was performed. Clinical notes of referring physicians for EMG/NCS and final EMG/NCS reports were reviewed for referring diagnoses, clinical history, physical exam and EMG diagnoses. Results Out of 472 patients diagnosed with CTS, 19.1% also had a concurrent diagnosis of CR confirmed by needle EMG ( n  = 90). 17.2% of suspected CTS based on clinical assessment were not confirmed after electrodiagnostic testing ( n  = 104). 29.0% of suspected CR patients were not confirmed after electrodiagnostic testing ( n  = 176). 12 clinical assessment data points (clinical history and physical exam findings) felt to represent a common evaluation of diagnoses of CTS were compiled. These included cervicogenic pain, radicular pain, hand paresthesias, nocturnal pain, symptoms worse with activity, symptoms relieved by shaking out hands (“flick” sign), myotomal weakness, dermatomal sensory abnormalities, hyporeflexia, loss of sensation in the median nerve distribution, thenar atrophy, and hand weakness. The only clinical finding found to have a clinically significant association with both CTS and CR was hand paresthesias ( p  = 0.001). Conclusion This series demonstrated that 19% of patients seen with CTS have an associated cervical radiculopathy. Without needle electromyography, these concurrent diagnoses would be missed, which can affect subsequent management and therapy. Clinical assessment alone may not be enough to distinguish between CTS and CR, as has been demonstrated in previous studies. Even though practice guidelines allude to optional needle EMG, this data provides a strong argument in favor of performing both NCS and needle EMG in patients with suspected CTS.