Analysis of parkinsonian tremor and rigidity relying on peripheral and central intensifying mechanisms through thalamic activities

Abstract

AbstractBackground and AimPassive and active muscle manipulations modify parkinsonian tremor and rigidity. We hypothesized that these outer maneuvers provoke thalamic 3 to 7‐Hz (τ‐range) and 13 to 27‐Hz (β‐band) activities, which in turn act to develop and maintain the symptoms. To test the hypothesis, we examined the temporal and quantitative relationships of the thalamic activities with the symptoms in conditions under the outer maneuvers.MethodsIn thalamotomy for 20 patients with Parkinson's disease, we monitored thalamic local field potentials and multiple unit spikes with surface electromyograms of neck and limb muscles.ResultsTremor is intensified in postural and kinetic modes with higher amplitude and faster frequency than the resting state, and in tremor rhythms on the cogwheel rigidity with accelerated muscle tone. Exaggerated thalamic τ‐range activities always led to tremor of those intensified modes. The τ‐range activities developed and maintained tremor in keeping a quantitative relationship in amplitude. Both the passive and active muscle manipulations transiently abolished the β‐band activities, and then made them relapse to lead to rigidity in a waning and waxing fashion. Because of these changes of β‐band activities, the patient's active effort to move or hold postures caused a state in conflict between voluntary and involuntary contractions.ConclusionTogether, the results suggest that passively activated peripheral kinesthetic afferents, and actively triggered central motor initiatives act to develop and maintain tremor and rigidity through the thalamic motor nuclei as the crucial relay stations.