Post-activation depression of the soleus H-reflex in stroke patients

Purpose: We examined post-activation depression in 35 stroke patients and 10 healthy subjects, and investigated whether their clinical symptoms were correlated to post-activation depression. Methods: Post-activation depression of the soleus H-reflex evoked by electrical stimulation of the common peroneal nerve with supramaximal intensity of motor response on the tibialis anterior muscle. Results: Post-activation depression was decreased on the affected side of the stroke patients. There was a significant difference between the affected and unaffected sides of the patients with post-activation depression, but no difference between the unaffected sides of the patients and healthy subjects. The presence of ankle clonus and the decrease in post-activation depression were correlated. Conclusion: Decreased post-activation depression in stroke patients suggests that a mechanism other than postsynaptic inhibition, such as reciprocal Ia inhibition and Ib inhibition, and presynaptic inhibition, may contribute to the exaggerated stretch reflexes, in particular, the manifestation of clonus.