Electrical impedance myography in healthy volunteers.

INTRODUCTION/AIMS: Electrical impedance myography (EIM) is a noninvasive technique being used in clinical studies to characterize muscle by phase, reactance, and resistance after application of a low-intensity current. The aim of this study was to obtain 50-kHz EIM data from healthy volunteers (HVs) for use in future clinical and research studies, perform reliability tests on EIM outcome measures, and compare findings with muscle ultrasound variables. METHODS: Four arm and four leg muscles of HVs were evaluated using an EIM device with two sensors, P/N 20-0045 and P/N 014-009. Muscles were evaluated individually and eight-muscle average (8MU), four-muscle upper extremity average, and four-muscle lower extremity average. An intraclass correlation coefficient (ICC) was applied to assess interrater, intrarater, and intersensor reliability using a subset of HVs. Ultrasound studies on muscle thickness and elastography were also performed on a subset of HVs. RESULTS: For the P/N 20-0045 sensor, the 8MU EIM mean and standard deviation (n = 41) was 14.54 ± 3.31 for phase, 7.04 ± 1.22 for reactance, and 28.91 ± 7.63 for resistance. Reliability for 8MU phase (n = 22) was good to excellent for both interrater (n = 22, ICC = 0.920, 95% CI 0.820 to 0.966) and intrarater (n = 22, ICC = 0.950, 95% CI 0.778 to 0.983). The P/N 014-009 sensor had similar reliability findings. Correlation analyses showed no association between EIM and muscle thickness. DISCUSSION: EIM is a reproducible measure of muscle physiology. Obtaining EIM values from HVs allows us to gain a better understanding how EIM may be altered in diseased muscle.

Adenosine A2A antagonists and Parkinson's disease.

Although there is no cure for Parkinson's disease (PD), there are several classes of medications with various mechanisms of action that can help improve the functionality of someone with PD. Dopamine derivatives are first line therapies for PD, hence dopamine receptor agonists (DAs) have been shown to improve functionality of symptoms in PD patients. The two main formulations of dopamine agonist medications in PD therapy are ergoline and non-ergoline derivatives. Additionally, it has been shown that PD can involve irregularities in other neurotransmitters, such as acetylcholine, norepinephrine, and serotonin, hence why non-dopaminergic medications are also vital in PD management. Examples include NMDA receptor antagonists, dopamine antagonists (i.e. neuroleptics), acetylcholine receptor antagonists, serotonin receptor 2A agonists, and adenosine A2 antagonists. In general, dopaminergic medications are the most effective in improving motor involvement with PD, whereas non-dopaminergic medications tend to focus on the non-motor involvement of PD. In this chapter, we will focus on the chemistry and medication background on dopaminergic vs non-dopaminergic therapy, with a focus of adenosine A2 antagonists at the end.

Electrical impedance myography (EIM) in a natural history study of C9ORF72 mutation carriers.

Objective: Electrical Impedance Myography (EIM) was used to evaluate disease progression in subjects with C9ORF72 expansion mutations and to assess correlations with Medical Research Council (MRC) Scale and revised ALS Functional Rating Scale (ALSFRS-R) measurements. Four types of clinical presentations were assessed; Amyotrophic Lateral Sclerosis (ALS), Frontotemporal dementia (FTD) or other dementia, ALS-FTD, and asymptomatic (ASYMP). Methods: Subjects were divided into an ALS Group (ALS/ALS-FTD) and non-ALS Group (FTD/ASYMP) based on initial visit and evaluated at 0, 6, 18, and 30 months with EIM of 4 arm and 4 leg muscles, ALSFRS-R, and MRC scales. The change in EIM from baseline and correlation with the functional scale and strength testing were analyzed. Results: EIM 50kHz phase values significantly declined over time in the ALS group (n = 31) compared to the non-ALS group (FTD/ASYMP) (n = 19). In the ALS group, the decline in EIM was correlated with decline in the ALSFRS-R and MRC scores using within-subject correlations. Conclusion: In clinical trials with small populations of genetically associated ALS such as C9ORF-related ALS, EIM may be a useful quantitative biomarker. We did not detect decline in asymptomatic subjects, but longer term studies may detect early changes in this group.