Testing of the refractory period in sensory nerve fibres is the most sensitive method to assess beginning polyneuropathy in diabetics.
BACKGROUND
In patients with diabetes mellitus (DM) without any clinical signs of polyneuropathy neurophysiological examinations intend to find early involvement of peripheral nerves. Conventionally, nerve conduction velocity (NCV) measurements of sensory nerves are performed. The purpose of this study is to investigate wether refractory period measurements may be more sensitive.


METHODS
We compared 30 IDDM/NIDDM diabetics without clinical signs of neuropathy (25 male, 5 female, age 45-73 years, mean 64.3 years) with age-matched controls. Sensible nerve conduction velocity (NCV) of radialis and suralis nerves were performed at 37 degrees C as well as double stimulations. The interstimulus interval were decreased stepwise by 0.2 ms beginning with 4.6 ms to determine the end of the relative refractory period.


RESULTS
Statistically significant differences of NCV and refractory period were found. The most profound differences between diabetics and normals were seen in refractory period of n. suralis. Regarding the 95% percentile as cut-off value of the normal range, pathological NCV of N. suralis were found in 4 patients. Pathological refractory period, however, were found in 9 patients.


CONCLUSIONS
Refractory period measurements of N. suralis are more sensitive than conventional NCV assessment in detection of beginning dysfunction in peripheral nerves of patients with diabetes mellitus without clinical signs of polyneuropathy.
Braune
H J
HJ
Dept. of Neurology, University Hospital, Germany. brauneh@mailer.uni-marburg.de
D000328:Adult; D000368:Aged; D003922:Diabetes Mellitus, Type 1 / Q000175:diagnosis / Q000503:physiopathology; D003924:Diabetes Mellitus, Type 2 / Q000175:diagnosis / Q000503:physiopathology; D003929:Diabetic Neuropathies / Q000175:diagnosis* / Q000503:physiopathology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009412:Nerve Fibers / Q000502:physiology*; D012032:Refractory Period, Electrophysiological / Q000502:physiology*; D012680:Sensitivity and Specificity; D011984:Sensory Receptor Cells / Q000502:physiology*; D009435:Synaptic Transmission / Q000502:physiology