Optimizing electrical impedance myography of the tongue in amyotrophic lateral sclerosis.

Abstract

Electrical impedance myography (EIM) can quantify muscle health at a range of frequencies, including that most commonly employed, 50 kHz. However, disease-related changes in EIM data suggest the distinction between normal and patient EIM values could be more apparent at frequencies of >50 kHz. We investigated at what other selected frequencies tongue EIM may differentiate healthy individuals and amyotrophic lateral sclerosis (ALS) patients, remain reliable, and correlate with a standard metric of bulbar function. Tongue EIM phase data from 30 volunteers and 11 ALS patients were analyzed at 6 discrete frequencies from 50 to 500 kHz. Of the frequencies assessed, EIM demonstrated maximal separation and reliability at 100 kHz, where phase value was also significantly correlated with the bulbar subscore on the revised version of the ALS Functional Rating Scale. One hundred kilohertz could serve as an optimal frequency at which to measure EIM phase values of the tongue in ALS. Muscle Nerve 55: 539-543, 2017.