Nerve conduction velocity is the typical clinical examination of nerves function for people with peripheral neuropathy, but a measure of only a segment of a reflexive arc. H-index, as the time course measurement of the H-reflex, is influenced by the conduction times of both sensory and motor nerves involved, as well as the central delay in the spinal cord. Therefore, H-index would provide a more comprehensive picture of a spinal reflexive arc. However, there is no report in regarding the relationship between nerve conduction velocity and H-index.
PURPOSE: This study was aimed at the understanding of the relationship between H-index, outcomes of H-reflex, and nerve conduction velocity in healthy elderly adults.
METHODS: Six participants (1 male, 5 female) were recruited. Body mass, height and age were recorded. Skin temperature was above 31°C before testing. H-reflex was tested at the soleus muscle (Zhang, Holmes, & Li, 2014); proximal sural nerve conduction velocity was tested to represent sensory nerve conduction velocity (SCV) (Burke, Skuse, & Lethlean, 1974); and tibial nerve conduction velocity was tested as a representation of the motor nerve conduction velocity (MCV) (Buschbacher, 1999). The H-index, Hpeak, Mpeak, H/M ratio (ratio of Hpeak / Mpeak), SCV and MCV were recorded and pooled into Pearson correlation test.
RESULTS: The average age (71 ± 8 years old), height (163 ± 8 cm), body mass (82 ± 25 kg), H-index (76 ± 17), Mpeak (4 ± 2 mv), Hpeak (1.0 ± 0.7 mv), H/M ration (0.3 ± 0.2), SCV (23 ± 3 m/s) and MCV (29 ± 2 m/s) were observed. Significant positive correlations were observed between H-index and SCV (r = .8) as well as Mpeak (r = .8). Significant negative correlation was observed between H-index and H/M ratio (r = -.7). No other significant correlation was observed between H-index and MCV as well as Hpeak.
CONCLUSIONS: Conduction time of sensory nerve is an influential component of H-index. The faster conduction time of the H-reflex loop, the less H/M ratio due to increased Mpeak.
Burke, et al. (1974). J. Neurol Neurosurg Psychiatry, 37(6), 647-52
Buschbacher. (1999). AmJ phys med Rehabil, 78(6), S15-20
Zhang, et al. (2014). IntJ Neurosci (0), 1-17.