New York Medical College (New York)
Anam Salman1,2, Barbara Lear2, Tanya Lehky, M.D.2
1New York Medical College, Valhalla, NY and
2National Institute of Neurological Disorders and Stroke, NIH, Bethesda, MD
Electrodiagnostic techniques are currently used to study neuromuscular disorders. In degenerative disease, muscle fibers are lost and replaced by fibrous tissue which alters the electrical properties of muscle tissue. Changes in the composition and architecture of the tissue via atrophy and loss of muscle fibers will affect the impedance values, therefore allowing the ability to monitor disease progression. Current limitations of electrodiagnostic techniques include the inability to monitor disease progression and invasive testing procedures. Electrical impedance myography is an emerging electrodiagnostic techniques which measures bioimpedance. High frequency, low intensity electrical current is applied to a muscle and the resulting voltage is measured. Resistance, reactance and phase angle of the muscle are then calculated. EIM was tested on ten muscles of 10 healthy adult volunteers to collect normative values. Preliminary analysis demonstrates that EIM is a reproducible test between sessions and between raters. EIM was also tested on the muscles of 37 pediatric patients with congenital muscular disorder. The resultant values were compared to the EIM normative controls obtained from healthy adult volunteers. Preliminary analysis demonstrates there is a significant difference in the resistance of all muscles and phase angle of most muscles tested between these two populations. This can be attributed to the atrophy of diseased muscle or to a difference between the properties of adult versus pediatric muscle. However, more normative values for healthy adults and pediatrics still need to be collected before conclusions can be drawn. EIM remains to be a quick, non invasive, painless, and easy to perform test, which has the potential to be used as a biomarker in clinical trials to follow the progression of neuromuscular disease.
Last updated November 25, 2013