BACKGROUND: Carpal tunnel syndrome (CTS) is the most common type of peripheral 
nerve entrapment and is a significant cause of morbidity. Carpal tunnel syndrome 
(CTS) has more incidences in diabetic patients. It has been suggested that 
insulin has an effect on nerve regeneration similar to that of nerve growth 
factor (NGF). Therefore, we aimed to evaluate the effectiveness of local insulin 
injection on the median nerve in patients with non-insulin-dependent diabetes 
mellitus (NIDDM) who have mild-to-moderate carpal tunnel syndrome (CTS).
MATERIALS AND METHODS: We carried out a prospective, randomized, single-blind, 
case-controlled study in these patients. We randomly selected 50 patients, 20 of 
whom had bilateral mild-moderate CTS. Therefore we had 70 hands and categorized 
them into two groups. At the baseline we injected NPH insulin (10U) directly 
into the carpal tunnel in group 1, and performed physiotherapy for the other 
group (group 2). Two weeks later, NPH insulin (10U) was injected into the carpal 
tunnel again and we continued physiotherapy for group 2. Electrodiagnostic study 
was performed for these two groups before treatment and 4 weeks after the last 
injection and physiotherapy. The patients were followed up for 6 weeks.
RESULTS: In both groups decrement of distal motor latency (DML) of the median 
nerves statistically was significant. In both groups, the increment of the 
sensory nerve conduction velocity was statistically significant. Also the 
decrement of pain, paresthesia, numbness, weakness/clumsiness and nocturnal 
awaking was statistically significant in both groups. But there was no 
significant difference between the two groups.
CONCLUSION: Local insulin injection is an effective and safe treatment for 
carpal tunnel syndrome in NIDDM patients as physiotherapy