Nerve conduction studies in diabetics presymptomatic and symptomatic for diabetic polyneuropathy.

Objective: We performed nerve conduction studies (NCS) on diabetics with and without symptoms of diabetic polyneuropathy (DPN) and evaluated correlations with glycaemic control and clinical features.

Methods: Consecutive patients were recruited in three groups: "normals" (nondiabetics without peripheral nerve disease); "presymptomatic diabetics" (diabetes without DPN); and "symptomatic diabetics". Clinical questionnaire and neurological examination were administered, and NCS were performed using standard techniques.

Results: 153 patients were recruited (51 normals, 50 presymptomatic diabetics, 52 symptomatic). Glycosylated haemoglobin and duration of DM were higher in symptomatic diabetics, with symptoms present for 1-60 months (mean 14.5). Alterations in NCS included prolonged latencies, lowered amplitudes and slowed conduction velocities, following a pattern of initially reduced sensory amplitudes and slowed motor velocities, with later reduced motor and sensory amplitudes and prolonged motor latencies. Neuropathic pain, clinical signs and glycosylated haemoglobin correlated with these changes.

Conclusions: Even in asymptomatic patients, NCS show diffuse changes, in a predictable pattern. Electrophysiological parameters correlate with neuropathic pain, physical findings and glycosylated haemoglobin levels.

Significance: We demonstrate that NCS changes in DPN follow a predictable pattern, correlating with clinical features and long-term glycaemic control.