Diagnostic Usefullness of Current Perception Threshold Test in Carpal Tunnel Syndrome

Background: Carpal tunnel syndrome (CTS) is the most commonly reported nerve entrapment syndrome. When performing routine nerve conduction studies (NCS) in clinically diagnosed CTS, we sometimes confronted with patients who have no definite electrophysiological evidence of CTS. Current perception threshold (CPT) test can evaluate the functioning of all major subpopulations of sensory nerve. The purpose of this study is to determine clinically usefulness of the CPT test in idiopathic CTS. Methods: We prospectively studied 60 patients (90 hands) who were clinically diagnosed as CTS. Involved hands were grouped into three clinical grades (mild, moderate and severe). NCS was done using a standard technique and equipment. CPT test was measured at the distal interphalangeal joint of second, third and fifth fingers with electrical current of 5 Hz, 250 Hz and 2,000 Hz in frequency. Results: Of 60 patients (90 hands), 8 (13.1%) were men and 52 (86.9%) were women. Mean age at evaluation was 56.00±8.94 years old. Positive rate of NCS and CPT was 0.80 (0.72, 0.88) and 0.61 (0.51, 0.71), respectively. Sensitive and specificity of CPT test was 0.49 and 0.57. As the clinical severity of CTS deteriorate, CPT test showed abnormality in low frequency stimulation. Conclusions: CPT test is an effective and relatively simple procedure for measuring perception in CTS. But CTS test is difficulty and subjectively at interpretation. We suggested that the usefullness of CPT test is lower than NC