Studies on induced exacerbation of Parkinsonian rigidity: The effect of contralateral voluntary activity.

Recent increasing interest in surgery of the basal ganglia for tremor and rigidity in Parkinsonism would seem to warrant more critical measures for evaluating these symptoms, not only for the purpose of assessing surgical results but also to elucidate the underlying neurological mechanisms. Parkinsonian symptoms, especially rigidity and tremor, are frequently unstable and may vary with the patient's environment, emotion, stress, and many other factors. Consequently, a clinical evaluation of these symptoms should be made with a method which can yield relatively reliable values as well as reveal the variability of the symptom in each patient. In our clinic Parkinsonian patients have been examined routinely with different methods of reinforcement to induce accentuation of rigidity and tremor or other symptoms. It was empirically concluded that active movement of the contralateral limbs is a simple and revealing method to elicit or exaggerate Parkinsonian rigidity. The purpose of this paper is to report a clinical and electromyographic study of Parkinsonian rigidity thus augmented.