Influence of dopaminergic treatment on resting elbow joint angle control mechanisms in patients with Parkinson’s disease – a preliminary report

Heightened tonic stretch reflex contributes to increased muscle tone and a more-flexed resting elbow joint angle (EJA) in patients with Parkinson’s disease (PD). Dopaminergic medication restores central nervous system (CNS) functioning and decreases resting muscle electrical and mechanical activities. This study aimed to evaluate the effects of dopaminergic medication on parkinsonian rigidity, resting EJA, resting electrical activity (electromyography, EMG) and mechanical properties (myotonometry, MYO) of elbow flexor muscles and the associations of EJA with these muscles resting electrical activity and mechanical properties in PD patients. We also evaluated a relationship between dopaminergic treatment dose and these outcome measures values. Methods: Ten PD patients (age 68 ± 10.1 years; body mass 70 ± 16.8 kg; height 162 ± 6.6 cm; illness duration 9 ± 4.5 years) were tested during medication on- and off-phases. Resting EJA, myotonometric muscle stiffness (S-MYO) and root mean square electromyogram amplitude (RMS-EMG) were recorded from relaxed biceps brachii and brachioradialis muscles. Based on the above parameters, we also calculated the EJA/S-MYO ratio and EJA/RMS-EMG ratio. Parkinsonian rigidity was assessed using the motor section of the Unified Parkinson’s Disease Rating Scale. Results: EJA, EJA/S-MYO ratio, and EJA/RMS-EMG ratio were increased and S-MYO, RMS-EMG, and parkinsonian rigidity were decreased during the medication on-phase compared with the off-phase. In addition, the dopaminergic treatment dose was negatively correlated with S-MYO and RMS-EMG, and positively correlated with EJA/SMYO and EJA/RMS-EMG ratios. Conclusions: We conclude that dopaminergic medication-induced improvements in resting elbow joint angle in tested patients with PD are related to changes in their muscle electrical and mechanical properties

Demographic and clinical data of the cancer-related fatigue group.

<p>¹ F - female, M- male</p><p>² R - right, L - left</p><p>³ BMI  =  Body Mass Index</p><p>⁴ ECOG  =  Eastern Cooperative Oncology Group Score is used to assess how a patient's disease is progressing and how the disease affects the daily living abilities of the patient (0–5). A score of 0 is considered fully active, able to carry on all pre-disease performance without restriction and 5 is considered dead.</p

An illustration of raw EMG and force recordings from a control and CRF patient.

<p>The EMG increased gradually in all 3 muscles (biceps brachii - BB, brachioradialis - BR, and triceps brachii - TB) during and the force was maintained on target throughout the sustained contraction for both the control and CRF subjects.</p

Group results of EMG mean power frequency (MPF) in biceps brachii (BB), brachioradialis (BR), and triceps brachii (TB) muscles at stages of minimal, moderate and severe fatigue.

<p>CRF group showed a lower degree of MPF reductions at moderate and severe fatigue stages especially for all 3 muscles, suggesting less muscle fatigue. MPF in CRF patients at minimal fatigue was similar to MPF at severe fatigue in controls. (A) The EMG mean power frequency in biceps brachii. (B) The EMG mean power frequency in brachioradialis. (C) The EMG mean power frequency in triceps brachii. * - Significant differences between fatigue stages, <i>P<0.05</i>; # - Significant differences between CRF patients and healthy controls <i>P<0.05</i>.</p

Group results of EMG amplitude (RMS in µV) in biceps brachii (BB), brachioradialis (BR), and triceps brachii (TB) muscles at stages of minimal, moderate and severe fatigue.

<p>CRF group showed smaller increases in EMG amplitude at moderate and severe fatigue stages especially for the BB (biceps brachii) and TB (triceps brachii) muscles, indicating a lower level of muscle fatigue. (A) The EMG amplitude in biceps brachii. (B) The EMG amplitude in brachioradialis. (C) The EMG amplitude in triceps brachii. * - Significant differences between fatigue stages, <i>P<0.05</i>.</p