Ratio of motor nerve conduction velocity to F-wave conduction velocity in diabetic neuropathy.

OBJECTIVE To investigate the usefulness of a new parameter, the ratio of motor nerve conduction velocity to F-wave conduction velocity (M/F ratio), for the differential diagnosis of diabetic neuropathy. RESEARCH DESIGN AND METHODS Nerve conduction studies were conducted in 95 patients with diabetic neuropathy, 44 nondiabetic patients with peripheral neuropathy, and 24 normal control subjects. Nondiabetic patients with neuropathy were grouped by clinical diagnosis as follows: segmental demyelination (n = 15), axonal neuropathy (n = 11), alcoholic polyneuropathy (n = 4), and other polyneuropathy (n = 14). Motor nerve conduction velocity (MCV) of post-tibial nerves, sensory nerve conduction velocity (SCV) of sural nerves, and F-wave conduction velocity (FWCV) of post-tibial nerves were measured by standardized techniques. The M/F ratio was calculated from these measurements. RESULTS The MCV and SCV of diabetic patients were significantly slower and the M/F ratio was significantly lower than those of normal subjects: MCV, 43.7 +/- 5.4 vs. 47.1 +/- 2.9 m/s, P < 0.001; SCV, 44.7 +/- 11.1 vs. 48.3 +/- 5.7 m/s, P < 0.05; M/F ratio, 0.84 +/- 0.09 vs. 0.90 +/- 0.06, P < 0.001. The FWCV of nondiabetic patients with neuropathy was significantly slower (40.0 +/- 6.3 vs. 48.3 +/- 4.0 m/s, P < 0.001) and the M/F ratio was significantly higher (1.04 +/- 0.12, P < 0.001) than that of normal subjects, respectively. Although MCV, SCV, and FWCV were correlated with age in normal control subjects, the M/F ratio was independent of age in the diabetic as well as the nondiabetic patients with neuropathy. CONCLUSIONS Results suggest that the M/F ratio, which is influenced by the neuronal damages in the distal segment of peripheral nerves, is useful in the differential diagnosis of diabetic neuropathy.