Effects of one year of near-normoglycemia on peripheral nerve function in type 1 (insulin-dependent) diabetic patients.

Ninety poorly controlled C-peptide negative type 1 (insulin-dependent) diabetic patients with chronic complications were allocated to intensified insulin treatment with either continuous subcutaneous insulin infusion or multiple insulin injections; 83 were studied over 1 year (seven patients dropped out of the study). Peripheral nerve function was assessed by clinical examination, malleolar vibration perception threshold, and motor and sensory nerve conduction velocities (MNCV; SNCV) in the median, ulnar, peroneal, and sural nerves. In order to assess the effect of metabolic control on peripheral nerve function, the results in patients with normal mean HbA1 levels during months 3-12 of the study less than 8.6% (tight control (tc); n = 50) were compared with those with abnormal mean HbA1 greater than or equal to 8.6% (poor control (pc); n = 33). Mean blood glucose was significantly higher in pc than in tc at months 2-9 and 11 (P less than 0.05). In pc median and ulnar SNCV were significantly lower at 6 and 12 months, and ulnar and peroneal MNCV at 12 months than in tc (P less than 0.05). No significant differences between the groups were observed for median MNCV, sural SNCV, and vibration sensation. Further analysis revealed that in well-controlled patients who showed abnormal peripheral nerve tests at baseline, median, and ulnar MNCV and SNCV but not peroneal MNCV, sural SNCV, and vibration sensation were significantly improved after 12 months as compared with poorly controlled patients with initially abnormal tests (P less than 0.05). There were no differences in nerve function between well- and poorly-controlled patients who had normal nerve tests at baseline.(ABSTRACT TRUNCATED AT 250 WORDS)