Restorative-neurological study for central motor disorders using spinal reflex

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1.Inappropriate cortical motor control in Parkinson's disease (PD) : We examined conditioning effects of transcranial magnetic stimulation (TMS) on the soleus H-reflex. Short latency subthreshold TMS stimulation at an intensity that kept -5% of the motor threshold in each situation did not facilitate the soleus H-reflex during tonic plantarflexion (PF) nor at PF onset in the patients with Parkinson's disease, as was the case for normal subjects. In some patients, paradoxical inhibition appeared at PF onset. The facilitation increase at PF onset, as compared to that at rest, was negatively correlated to UPDRS and to the rigidity grade. Pallidotomy improved both this modulation and the clinical scores. Cortical activity for the proper execution of reciprocal control between the agonist and antagonist is disturbed in PD.2.Abnormal α-γ linkage in Parkinson's disease : We examined this as a size of tendon reflex in PD. Soleus H-reflex and T-reflex evoked by tendon tap with a mechanical stimulator were recorded at rest, during tonic PF, and at the onset of PF. The maximal H-reflex (Hmax) at rest was 55% of the maximal M-response and T-reflex (Tmax) 30% in normal subjects, and they were 36 and 31% respectively in PD. The size ratio of Tmax and Hmax (Tmax/Hmax) at rest in PD was larger than normal, which was correlated with the grade of rigidity, bradykinesia, Hoehn & Yahr stage, and time for 10m gait. Tmax was correlated with bradykinesia and time for 10m gait. There were no such correlations between Hmax and any clinical findings. In PD, the size of H-reflex increased with TPF as in normal subjects, but T-reflex decreased during TPF that was opposite of normal. These findings indicate that the fusimotor activity might be increased at rest and decreased during TPF in PD, which may reflect inappropriate α-γ linkage in PD.