Median and ulnar ring flnger sensory conduction velocity in mild carpal tunnel syndrome

Objective To find a sensitive electrodiagnostic method for patients with mild carpal tunnel syndrome (CTS). Methods 29 hands with recent onset symptoms and signs of CTS but with normal median distal motor latency, and 23 sex and age-matched normal controls (25 hands) were studied and the sensory conduction velocity ( SCV ) was recorded from the fourth digit ( D4 ) and the third digit ( D3 ) . Results D4 ulnar nerve (UN) SCV 45. 2 m/s, median nerve (MN) SCV 44. 1 m/s, and (or) the median and ulnar sensory conduction velocity difference 8. 1 m/s were considered to be confirmed with the diagnosis of CTS. While the abnormal rate from MN D3 was 66% , and MN D4, 76% , with a SCV different rate between D4 MN and UN being 93%. There appeared a double-peak potential measured over the median nerve with CTS after D4 stimulation (8/14 hand) but not found in control hands. Conclusion Comparison of median and ulnar D4 SCV should be a very sensitive method for detecting mild CTS. The median and ulnar sensory conduction velocity difference 8. 1 m/s and (or) double peak potential recorded over the median nerve allows immediate dignosis of CTS. The ring finger technique should be recorded for the early diagnosis of CTS.