Lower / upper extremity F-wave ratio for detecting early diabetic neuropathy.

Background And Purpose: Results of conventional nerve conduction studies may be within normal limits in early diabetic neuropathy. Previous studies demonstrated that F-wave latency should be used to detect this early neuropathic process. The aim of this study is to evaluate the sensitivity of lower/upper extremity F latency ratios in detecting the early neuropathy in patients with diabetic neuropathic pain.

Methods: 44 patients with diabetic neuropathic pain (DNP) and 44 control subjects whose both conventional nerve conduction studies and F-wave latencies were within normal limits were included to the study. We compared the nerve conduction parameters and lower/upper extremity (tibial/ulnar) F latency ratios of the groups.

Results: Tibial F latency was significantly prolonged and tibial/ulnar F latency ratio was significantly higher in DNP group. Our results support that F-waves are useful for detecting early diabetic neuropathy and suggest that comparison with a control group will demonstrate a difference even when the individuals' F-wave latencies are within the normal limits. The difference was significant for tibial but not for ulnar F latency values supporting the length dependent involvement. The tibial/ ulnar F-wave latency ratio was significantly higher in the DNP group, suggesting that it might also be useful to detect early neuropathy and to demonstrate that the underlying process was predominant in lower extremity.

Conclusion: Further studies may provide additional information about the utility of this ratio for detecting early neuropathy even when F-wave latencies are within normal limits.