The effect of subthalamic nucleus stimulation on autogenic inhibition in Parkinson disease

BACKGROUND: Recent animal experiments suggest an important role of descending input from basal ganglia to brainstem and via the reticulospinal tract (RST) to spinal cord in the genesis of motor symptoms in Parkinson disease (PD). In humans, a marker for RST activity is Ib mediated autogenic inhibition, which is reduced in PD patients. The authors investigated the effect of high frequency stimulation of the subthalamic nucleus (STN-HFS) on autogenic inhibition in PD.

METHODS: In 10 controls and 10 PD patients with chronically implanted STN electrodes, the soleus H-reflex conditioned by gastrocnemius nerve stimulation (interstimulus interval 2 to 10 msec) was used to examine the effect of STN-HFS on the activity of Ib spinal interneurons.

RESULTS: STN-HFS was able to restore the abnormally reduced autogenic inhibition. The H-reflex changes during STN-HFS significantly correlated with the clinical improvement of gait and posture.

CONCLUSIONS: Observed changes in spinal autogenic inhibition may allow measurement of the contribution of subcortical routes to the STN-HFS induced motor benefit in PD.