Motor and sensory neuroconduction in patients with carpal tunnel syndrome and diabetic polyneuropathy

Introduction. The combination of carpal tunnel syndrome and diabetic polyneuropathy is common, and it is important to establish the correct diagnosis since carpal tunnel syndrome can be successfully treated by surgery, even in diabetic patients. Both conditions have similar clinical features and the usual neurophysiological investigations show very similar results. Objective. To determine the differential diagnosis between carpal tunnel syndrome and diabetic polyneuropathyP. Patients and methods. Sensory and motor neuro-conduction studies were done on the median and ulnar nerves of a group of 30 healthy persons (group A), 30 patients with a history of carpal tunnel syndrome (group B) and 30 patients with diabetes mellitus type I or type II (group C) with diabetic polyneuropathy. The physiological variables in which the greatest differences were seen in the three groups were: the speed of sensory conduction in the palm-third finger segment of the median nerve, distal latency obtained on stimulation of the fourth finger, distal motor latency of the median nerve and distal latency of the sensory potentials obtained by stimulation at the wrist and recorded at the fourth finger. Results and conclusions. With these variables for prediction, carpal tunnel syndrome was detected in 30% of the patients classified initially on clinical grounds as having diabetic polyneuropathy, and 60% of the patients were correctly reclassified after being initially classified on clinical grounds as having carpal tunnel syndrome [REV NEUROL 1999; 28: 1147-52].