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Electrical Impedance Myography (EIM)
Electrical Impedance Myography (EIM)
| Availability |
More information available here: Electrical Impedance Myography
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| Classification |
Exploratory: Facioscapulohumeral Muscular Dystrophy (FSHD) and Congenital Muscular Dystrophy (CMD)
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| Short Description of Instrument |
Electrical impedance myography (EIM) is a non-invasive technique for the evaluation of neuromuscular disease that relies upon the application and measurement of high-frequency, low-intensity electrical current. EIM assesses disease-induced changes to muscle's normal composition and architecture, including myocyte atrophy and loss, edema, reinnervation, and the deposition of endomysial connective tissue and fat. With application of single-frequency electrical current, EIM can be used to help grade the severity of neuromuscular disease. Assessing electrical impedance across a spectrum of applied frequencies and with current flow at multiple orientations relative to the major muscle fiber direction can provide a more complete picture of muscle condition. EIM does not focus on measuring the inherent electrical activity of the tissues. Like diagnostic ultrasound, measurements are made over a small area of interest, with energy being applied to the body and the resultant surface patterns analyzed.
Methodology:
EIM measures the impedance of skeletal muscle over a frequency range between 1 kHz and 10 MHz. The impedance is measured at each frequency by applying low-intensity electrical current (<1 mA) via surface electrodes, and measuring the resulting voltage signals using a second set of surface electrodes, converting them into 2 impedance parameters, the resistance (R) and the reactance (X). The resistance and reactance can be used to calculate the phase angle.
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| References |
EIM in clinical research (General):
Rutkove SB. Electrical impedance myography: Background, current state, and future directions. Muscle Nerve. 2009; 40(6): 936-946.
Esper GJ, Shiffman CA, Aaron R, Lee KS, Rutkove SB. Assessing neuromuscular disease with multifrequency electrical impedance myography. Muscle Nerve. 2006;34(5):595-602.
Rutkove SB, Sanchez B. Electrical Impedance Methods in Neuromuscular Assessment: An Overview. Cold Spring Harb Perspect Med. 2019;9(10):a034405.
Sanchez B, Rutkove SB. Present Uses, Future Applications, and Technical Underpinnings of Electrical Impedance Myography. Curr Neurol Neurosci Rep. 2017;17(11):86.
Sanchez B, Rutkove SB. Electrical Impedance Myography and Its Applications in Neuromuscular Disorders. Neurotherapeutics. 2017;14(1):107-118.
Disease-specific recommendations:
EIM in ALS:
Rutkove SB, Caress JB, Cartwright MS, Burns TM, Warder J, David WS, Goyal N, Maragakis NJ, Benatar M, Sharma KR, Narayanaswami P, Raynor EM, Watson ML, Shefner JM. Electrical impedance myography correlates with standard measures of ALS severity. Muscle Nerve. 2014;49(3):441-443.
Rutkove SB, Caress JB, Cartwright MS, Burns TM, Warder J, David WS, Goyal N, Maragakis NJ, Clawson L, Benatar M, Usher S, Sharma KR, Gautam S, Narayanaswami P, Raynor EM, Watson ML, Shefner JM. Electrical impedance myography as a biomarker to assess ALS progression. Amyotroph Lateral Scler. 2012;13(5):439-445.
EIM: in CMD:
Schwartz DP, Dastgir J, Salman A, Lear B, BÖnnemann CG, Lehky TJ. Electrical impedance myography discriminates congenital muscular dystrophy from controls. Muscle Nerve. 2016;53(3):402-406.
EIM in Duchenne Muscular Dystrophy:
Schwartz S, Geisbush TR, Mijailovic A, Pasternak A, Darras BT, Rutkove SB. Optimizing electrical impedance myography measurements by using a multifrequency ratio: a study in Duchenne muscular dystrophy. Clin Neurophysiol. 2015;126(1):202-208.
EIM in FSHD:
Statland JM, Heatwole C, Eichinger K, Dilek N, Martens WB, Tawil R. Electrical impedance myography in facioscapulohumeral muscular dystrophy. Muscle Nerve. 2016;54(4):696-701.
Mul K, Heatwole C, Eichinger K, Dilek N, Martens WB, Van Engelen BGM, Tawil R, Statland JM. Electrical impedance myography in facioscapulohumeral muscular dystrophy: A 1-year follow-up study. Muscle Nerve. 2018;58(2):213-218.
EIM in SMA:
Rutkove SB, Shefner JM, Gregas M, Butler H, Caracciolo J, Lin C, Fogerson PM, Mongiovi P, Darras BT. Characterizing spinal muscular atrophy with electrical impedance myography. Muscle Nerve. 2010;42(6):915-921.
Description of Portable EIM system:
Ogunnika OT, Rutkove SB, Ma H, Fogerson PM, Scharfstein M, Cooper RC, Dawson JL. A portable system for the assessment of neuromuscular diseases with electrical impedance myography. J Med Eng Technol. 2010;34(7-8):377-385.
Document last updated July 2021
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