Early detection of diabetic neuropathy: a neurophysiological study on 100 patients

As a long-term complication of diabetes mellitus, autonomic neuropathy has received considerable attention in the last few years since a tripled 5-year-mortality of patients with diabetic neuropathy including autonomic disturbances has been observed. In a total of 100 diabetics with clinical manifest neuropathy of different stages (N0 = 8, N1 = 15, N2a = 24, N2b = 28, N3 = 25), 26 of whom were insulin-dependent and 74 non-insulin-dependent, the validity of different neurophysiologic and autonomic function test procedures proposed in literature was assessed. Apart from clinical examination, nerve conduction velocity measurement of five nerves as well as amplitude measurement of evoked sensory and motor actin potentials, electromyography of at least four muscles of the lower limbs, and measurement of sympathetic skin response on hands and feet were performed. Furthermore, heart rate variation at deep periodical breathing (E/I-ratio), during Valsalva's manoeuver and after standing up (30/15-ratio) was determined. In addition, the drop in systolic blood pressure to standing up was measured. The further developed the clinical picture of neuropathy, the more pathological were the results obtained in different tests. The results suggest that most changes leading to pathological values of nerve conduction velocity and heart rate variation measurement take place in a clinical stage, in which no or only very slight clinical signs give evidence of diabetic neuropathy (N0-N1). Therefore, especially these examinations should be performed on diabetics with no or only slight clinical signs of neuropathy in order to reveal those with beginning neuropathic disturbances. EMG examination is preferable in later stages of the disease.