Clinical and Electrodiagnostic Testing of Carpal Tunnel Syndrome: A Narrative Review

Abstract

Carpal Tunnel Syndrome (CTS) is a pressure-induced neuropathy that causes sensorimotor disturbances of the median nerve, which impair functional ability. A clear history that elicits relevant personal and work exposures and the nature of symptoms can lead to a high probability of a correct diagnosis. Hand diagrams and diagnostic questionnaires are available to provide structure to this process. A variety of provocative tests have been described and have variable accuracy. The Phalen's wrist flexion and the carpal compression tests have the highest overall accuracy, while Tinel's nerve percussion test is more specific to axonal damage that may occur as a result of moderate to severe CTS. Sensory evaluation of light touch, vibration, or current perception thresholds can detect early sensory changes, whereas 2-point discrimination changes and thenar atrophy indicate loss of nerve fibers occurring with more severe disease. Electrodiagnosis can encompass a variety of tests and is commonly used to assess the presence/severity of neuropathic changes and to preclude alternative diagnoses that overlap with CTS in presentation. The pathophysiologic changes occurring with different stages of nerve compression must be considered when interpreting diagnostic test results and predicting response to physical therapy management.

Relationship Between Interpretation and Accuracy of the Upper Limb Neurodynamic Test 1 in Carpal Tunnel Syndrome

“…8 As a consequence, no single clinical test has been accepted as sufficient to identify this disorder. 9,10 A frequently adopted tension test is the Upper Limb Neurodynamic Test 1 (ULNT1), which emphasizes tension on the median nerve, as reported by anatomical studies. [11][12][13][14][15] Butler 16 suggests to perform the test as follows: while preventing elevation of the shoulder girdle, the shoulder is abducted and the wrist is extended; supination of the forearm is followed by lateral rotation of the shoulder, elbow extension, and cervical lateral flexion, first away from the tested extremity and then toward the tested extremity.…”

Median versus ulnar medial thenar motor recording in diagnosis of carpal tunnel syndrome

“…There is a diversity of electrophysiological techniques that are utilized to assess median nerve conduction across carpal tunnel. Slowing of the median nerve across the carpal tunnel is the electrophysiological confirmation of clinical CTS [20]. These electrophysiological tests are the routine median motor and sensory conduction studies.…”

The consequences of stimulus intensity on sensory nerve action potentials

“…In contrast, however, most researchers use supramaximal stimulation when conducting sensory nerve conduction studies, whether it is to investigate pathologies such as Carpal Tunnel Syndrome (MacDermid and Doherty, 2004;Stevens, 1997), diabetic neuropathy (Dyck et al, 1985) or to develop normative data sets (Jablecki et al, 1993). Other researchers fail to report what level of stimulation that was used to generate SNAPs in their studies (Aydin et al, 2004;Rathakrishnan et al, 2007).…”