T32. A follow-up study of F Wave in 26 Type 2 Diabetes patients

Introduction We previously showed ( Pan et al., 2014 ) that an increased F-wave latency identified a subclinical diabetic polyneuropathy (DPN) in 23 of 64 (36%) asymptomatic patients at the onset of type 2 diabetes mellitus (DM). We have now conducted a follow up study in the remaining initially asymptomatic 41 patients to further analyze the time course of DPN and characterize early development of clinical and electrophysiological abnormalities. Methods Of 41 DM patients initially identified as normal clinically and electrophysiologically, 26 participated in the current study conducted during the 4–5th year after the onset of DM. The study consisted of neurological examination looking for symptoms and signs of neuropathy and electrodiagnostic evaluations, which comprised minimal (Fmin), maximal (Fmax) and mean F-wave latencies (Fmean), and motor and sensory nerve conduction study (MNCS and SNCS). We calculated the rate of abnormalities for clinical and electrophysiological findings, and compared the initial and follow up studies for Fmin, Fmean and Fmax, analyzing all 26 patients as a group. Results Of the 26 patients (15 men) under consideration, 4 had clinical symptom of foot numbness and pain, associated with normal electrophysiological study in 1, increased tibial nerve F-wave latency in 1 and combined abnormalities of tibial nerve F-wave and sural nerve SCNS in the other 2. Of the remaining 22 patients without clinical symptoms and signs, 4 showed a prolonged tibial nerve F-wave latency, and 18 had a normal electrodiagnostic study. Thus, 7 of 26 (27%) patients showed an increased tibial nerve Fmin latency 3 (11%) without Fmean or Fmax abnormalities, 2 (8%) with increased Fmean, and the other 2 (8%) with increased Fmean and Fmax. In contrast, only 2 of 26 (8%) patients had SNCS abnormalities of sural nerve. Analyzing all 26 patients as a group, comparison between initial and follow-up data, showed a significant difference for Fmin (45.3 ± 2.7 vs 47.9 ± 3.8 ms, t  = −4.873, P  = 0.000), Fmean (46.8 ± 3.0 vs 49.0 ± 3.8 ms, t  = −4.744, P  = 0.000) and Fmax (48.1 ± 3.2 vs 50.4 ± 3.9 ms, t  = −4.134, P  = 0.000). Conclusion The tibial nerve F-wave latencies rank the first to detect subclinical neuropathy in patients with type 2 diabetes during early stages. In particular, a study of Fmin latency yields better than SNCS of sural nerve, which also provides a sensitive measure of sensory abnormalities in this neuropathy.