Parkinson's disease rigidity

Abstract

We studied the EMG potentials evoked in the bilateral first dorsal interosseus muscle by electromagnetic stimulation of the corticomotoneuronal descending system in 10 Parkinson's disease patients and in 10 age- and sex-matched normal controls. We selected patients who did not have tremor but had predominant rigidity with asymmetric body involvement. On the rigid side of the PD patients, the threshold to cortical stimulation was lower than on the contralateral side or than normal values. On average, patients had normal central conduction times, but their motor evoked potentials (MEPs) on the rigid side were larger than those of controls when the cortical stimulus was at rest or during slight tonic contraction of the target muscle. In the latter condition, a silent period shorter than that of controls followed MEPs, whereas the peripheral silent period following ulnar nerve stimulation at the wrist was prolonged. Alpha motor neuron excitability, tested by the F-wave method, was enhanced on the rigid side at rest. In rigidity, spinal motor nuclei may be more responsive than normal to descending inputs from motor cortex, or the entire corticomotoneuron system may prove hyperexcitable under given conditions.

Role of hyperactive cerebellum and motor cortex in Parkinson's disease

“…For example, TMS studies have shown that there is defective cortico-cortical inhibition in motor cortex excitability (Kleine et al, 2001;Pierantozzi et al, 2001;Ridding et al, 1995). This causes a diffused and increased response in the motor cortex that possibly underlies rigidity (Cantello et al, 1991). In the current study, all of our patients had rigidity in the right upper limb ─ UPDRS scores from 1 to 3.…”

The Effect of Exercise Training in Improving Motor Performance and Corticomotor Excitability in People With Early Parkinson's Disease

“…Studies have shown a loss of cortical excitation and inhibition balance in PD with higher motor system excitability in patients with PD at rest compared with controls most likely the result of reduced intracortical inhibition. 14,15,44 Under tonic muscle contraction, shortened CSP in PD also suggests an enhanced excitability. 14 Inhibition as measured through CSP may be important for suppressing competing motor networks thereby facilitating cortical-basal ganglia loops specified for an intended motor action.…”

“…44 CSP durations are usually shorter in PD patients compared with controls and, within PD patients, are shorter on the more affected side compared with the less affected side. 14,45 Both CSP durations and parkinsonian symptoms are sensitive to dopaminergic medication. Similar to the observed effects of high-intensity exercise, CSP durations are prolonged in PD patients after taking levodopa, [45][46][47] apomorphine, 48 and pergolide, 19,49 drugs known to provide effective symptomatic relief of motor symptoms.…”

“…In general, these abnormalities reflect higher corticomotor excitability in PD compared with controls. [14][15][16][17] As CSP represents inhibitory influences on corticomotor excitability; higher excitability would be evident as a shortened CSP duration. In fact, shortened CSP durations are among the most consistent and widely reproduced TMS finding among PD patients.…”

Non-invasive brain stimulation for Parkinson’s disease: Current concepts and outlook 2015

“…These changes depend on the state of activation, whether tested at rest or during voluntary or involuntary motor activity. Cortical excitability is increased during rest and decreased during voluntary activity corresponding to reduced facilitation (Cantello et al, 1991;Valls-Sole et al, 1994). This concept is inferred from the motor evoked potential (MEP), which is subject to methodological limitations such as phase cancellation (Magistris, Rosler, Truffert, & Myers, 1998).…”