Electrical Impedance Myography in Neuromuscular Disorders

Electrical impedance myography (EIM) is a non-invasive electrophysiological technique that evaluates the bioelectrical properties of skeletal muscle through the application of multi-frequency alternating currents. By measuring the resistance and reactance of muscle tissue and deriving the phase angle, EIM offers a quantitative biomarker of muscle composition, membrane integrity and extracellular fluid distribution. Its rapid acquisition and minimal discomfort make it attractive for longitudinal monitoring of neuromuscular disorders, including amyotrophic lateral sclerosis, muscular dystrophies, sarcopenia and post-stroke paresis. Advances in electrode configuration, computational modelling and finite element analysis have improved signal reproducibility and depth resolution, while integration with imaging and machine-learning approaches holds promise for predictive diagnostics. Across both human and animal studies, EIM has demonstrated sensitivity to subtle morphofunctional changes, offering objective endpoints for clinical trials and potential for early diagnosis, treatment monitoring and assessment of therapeutic response.

Research from Nature Portfolio

Recent studies in animal models have established EIM as a sensitive tool for detecting age-related muscle atrophy. In adult zebrafish, reductions in phase angle and reactance at low frequencies corresponded closely with histological measures of muscle cross-sectional area and correlated with swimming performance metrics, underscoring EIM’s utility as a rapid biomarker of sarcopenia. Complementing this, novel multipolar needle methods have been developed to measure the complex permittivity of anisotropic skeletal muscle in situ, halving the number of insertions required and providing multi-depth impedance profiling that could inform needle-based assessments in clinical neuromuscular disease. Foundational guidelines on electrode positioning have also been articulated, quantifying the precision necessary to achieve reproducible resistance and reactance measurements in human and animal studies and thereby standardising EIM as a reliable biomarker across research centres.

Electrical Impedance Myography in Neuromuscular Disorders publication trend

The graph below shows the total number of articles in electrical impedance myography in neuromuscular disorders across all publications each year (not limited to Nature Index journals).

Technical terms

Electrical Impedance Myography (EIM): A technique that applies alternating current through muscle to measure its resistance and reactance, yielding quantitative biomarkers of tissue health.

Phase angle: The angular difference between current and voltage in impedance measurements, reflecting cell membrane integrity and tissue composition.

Resistance: The component of impedance denoting opposition to current flow through intra- and extracellular fluids.

Reactance: The frequency-dependent component of impedance associated with capacitive effects of cell membranes.

Permittivity: A measure of how a tissue stores and dissipates electrical energy, influencing both reactance and overall impedance.

References

1. Electrical impedance myography detects age-related skeletal muscle atrophy in adult zebrafish. Scientific Reports (2023).
2. New electrical impedance methods for the in situ measurement of the complex permittivity of anisotropic skeletal muscle using multipolar needles. Scientific Reports (2019).
3. Guidelines to electrode positioning for human and animal electrical impedance myography research. Scientific Reports (2016).
4. An Approach to Using Electrical Impedance Myography Signal Sensors to Assess Morphofunctional Changes in Tissue during Muscle Contraction. Biosensors (2024).
5. Electrical impedance myography combined with quantitative assessment techniques in paretic muscle of stroke survivors: Insights and challenges. Frontiers in Aging Neuroscience (2023).
6. A Technique for Performing Electrical Impedance Myography in the Mouse Hind Limb: Data in Normal and ALS SOD1 G93A Animals. PLOS ONE (2012).