Soleus H-reflex measures in patients with focal and generalized dystonia.

Objective: The purpose of this study was to examine neurophysiological characteristics of dystonia patients using electromyographic soleus H-reflex methods.

Methods: Thirty normal healthy individuals were compared to 27 patients with focal (cervical) or generalized dystonia. Three H-reflex assessment methods were included: the ratio of maximum H-reflex to direct muscle potential (H/M ratio); vibration inhibition (H(v)/H(c) ratio); and H-reflex recovery curves (HRRC).

Results: Average H/M ratios between groups were not statistically significant. The average H(v)/H(c) ratio for the generalized dystonia group was significantly greater than the focal dystonia and normal groups. Average values of the HRRC showed the generalized dystonia group had significantly greater disinhibition than the focal dystonia and control groups during the early inhibition phase. The HRRC for the focal dystonia group was greater than normal and more similar to the generalized dystonia group during the late phases of the recovery curve. The average value of the localized late facilitation phase for the focal dystonia group was significantly greater than the control group and less than the generalized dystonia group. No differences were observed between groups for the average localized late inhibition phase of the recovery curve.

Conclusions: Soleus H-reflex measures identified neurophysiologic differences between generalized dystonia, cervical dystonia and normal conditions.

Significance: This methodology enables analysis of the underlying characteristics of dystonic pathologies using soleus H-reflex methods rather than upper extremity H-reflex techniques.