SOLEUS H-REFLEX TESTS AND CLINICAL SIGNS OF THE UPPER MOTOR-NEURON SYNDROME

Soleus H-reflex tests are used for elucidating pathophysiological mech anisms in motor control. The cumulative vibratory inhibition of the so leus H-reflex, the ratio of the reflex to direct muscle potential (H t o M ratio) and the recovery curve of the soleus H-reflex were studied in 38 patients with varying signs of the upper motor neuron syndrome f or a possible relation with clinical features. The results were compar ed with those obtained from a group of healthy volunteers. The magnitu de of vibratory inhibition decreased with increase of hypertonia. The H to M ratio increased as the activity of the tendon reflex was enhanc ed and correlated to a lesser degree with muscle tone. Both the H to M ratio and late facilitation of the soleus H-reflex recovery curve wer e elevated in clonus. The findings suggest that alterations in the res ults of soleus H-reflex tests relate to specific clinical features of the upper motor neuron syndrome. Possible pathophysiological implicati ons are discussed.