STRETCH REFLEXES OF INDIVIDUAL PARKINSONIAN-PATIENTS STUDIED DURING CHANGES IN CLINICAL RIGIDITY FOLLOWING MEDICATION

Stretch reflexes were elicited in flexor carpi radialis (FCR) of healt hy subjects and patients with Parkinson's disease by forcible ramp and hold extensions of the wrist joint. Individual patients were studied Off treatment when rigidity was detected clinically at the joint and t hroughout the clinical response to anti-parkinsonian medication that a bolished or reduced their rigidity. In this way the possible effects o f inter-subject variability upon the relationship between reflex behav iour and rigidity were eliminated. The long-latency (M2) stretch refle xes of the patient group were increased on average compared to those o f healthy subjects. However, in the large majority of individual patie nts there were no significant correlations between the amplitudes of t heir M2 or total (short-latency (M1)+ M2) reflex activities, recorded off and on treatment, and the accompanying changes in clinically asses sed rigidity. These results suggest that parkinsonian rigidity cannot be uniquely attributed to the increased reflex responsiveness measured by the present laboratory techniques. However, the techniques used to test reflex function in our study differed in several respects (e.g., background activity, stretching wave form) from those employed during clinical assessment of rigidity so that the balance of reflex mechani sms may have varied in the two situations. Therefore, these results ca nnot be taken as definitive evidence against a reflex origin of rigidi ty.