Methods of H-reflex evaluation in the early stages of Parkinson's disease.

Differentiating the early stages of Parkinson's disease from the normal consequences of aging or from other common neurologic conditions can be diagnostically problematic. The purpose of this study was to compare methodologies for measuring motor neuron excitability of Parkinson's disease patients with a control group. H-reflexes were monitored in 16 patients diagnosed in the early stages of Parkinson's disease (Hoehn & Yahr stages I and II) compared with 30 subjects who were disease free. Methods of measurement included H-reflex latencies, the relative values of maximum H-reflexes to maximum direct motor responses (H-to-M ratio), the relative values of H-reflex amplitudes during vibration compared with control H-reflex amplitudes (Hv-to-Hc ratio), and double-stimulation H-reflex recovery curves using different interstimulus interval parameters. No significant differences were observed for the H-to-M or Hv-to-Hc ratios, or for the H-reflex latencies. The H-reflex recovery curves for the patients with Parkinson's disease demonstrated significantly greater ratio amplitudes than the control group during the double-stimulus responses between the 150-msec and 700-msec interstimulus intervals. Although comparisons of simple H-reflexes and H-reflexes during vibration did not differentiate the patients in the early stages of Parkinson's disease from the control group, the double-stimulation paradigm was a sensitive method for detecting early diagnoses of this disease.

The H-reflex modulation in lying and a semi-reclining (sitting) position.

OBJECTIVE: The purpose of this study was to compare motor pool excitability as measured by the H-reflex during lying prone and sitting in a semi-reclining position. DESIGN AND METHOD: Twelve volunteer subjects were measured for maximum M-wave and H-wave during sitting and prone lying to determine an H/M ratio. Latency of each H-reflex was also measured. H-reflex responses were recorded during a control and a vibration condition in the two positions. A double-stimuli H-reflex recovery curve was also plotted for each subject in each relaxed position of sitting and lying. RESULTS: No significant differences were observed between the prone lying and sitting positions for the any of the variables measured. CONCLUSIONS: The present results showed no difference in H-reflex responses between sitting or lying and it is suggested that the subject/patient should be tested in a position which is most comfortable.