Electrical impedance myography in the evaluation of the tongue musculature in amyotrophic lateral sclerosis

Abstract

Introduction Electrical impedance myography (EIM) quantifies muscle health and is used as a biomarker of muscle abnormalities in neurogenic and myopathic diseases. EIM has yet to be evaluated in the tongue musculature in people with amyotrophic lateral sclerosis (ALS), who often show clinical bulbar signs. Methods The lingual musculature of 19 subjects with motor neuron disease and 21 of normal participants were assessed using EIM, strength and endurance testing, and clinical observation. Results Tongue musculature in the ALS group was characterized by significantly smaller phase (Ph) and larger resistance (R) when compared to the healthy cohort. Ph and tongue endurance were correlated in the ALS group. Discussion EIM of tongue musculature could distinguish people with ALS from healthy controls. The demonstrated relationship between tongue function and Ph supports further testing of EIM of the tongue as a potential biomarker in ALS.

An improved electrical impedance myography (EIM) tongue array for use in clinical trials

“…The average EIM phase value was significantly lower in patients than in healthy volunteers, consistent with the results from the pilot tongue EIM study (Shellikeri et al, 2015). This reduction in phase is also observed when taking appendicular measurements in patients with both primary myopathic and denervating diseases such as ALS (Rutkove et al, 2014; Tarulli et al, 2005).…”

“…The tongue EIM ICCs are at least on par with the ICCs for test–retest reliability obtained using the Iowa Oral Performance Instrument, a standard measure of anterior tongue strength (Adams et al, 2014, 2015). Perhaps surprisingly, the tongue EIM repeatability data attained with the small array are also comparable to those previously reported for the larger tongue depressor EIM array (Shellikeri et al, 2015). EIM electrical current penetrates more deeply into tissue as the distance between electrodes on an array widens (Rutkove, 2009); therefore, larger EIM arrays are theoretically favored over smaller arrays.…”

“…The lingual EIM 50 kHz phase values of ALS patients were significantly lower than those of healthy volunteers, and correlated with another standard measure of tongue endurance (Shellikeri et al, 2015). However, the tongue depressor electrode array used in the study induced gag reflexes in many ALS patients.…”

Tongue electrical impedance in amyotrophic lateral sclerosis modeled using the finite element method

“…The farther apart the electrodes are spaced, the greater the current penetration and likely the greater the impact of tongue thickness. The length of our electrode array was intentionally short to minimize the likelihood of eliciting a gag reflex, which was a problem with the first-generation tongue array (Shellikeri et al, 2015). The resulting short electrode distance may have also have fortuitously reduced the impact of tongue atrophy on the measurements.…”

“…EIM has been shown to be sensitive to disease progression in appendicular muscles in ALS, in both human patients (Rutkove et al, 2012) and animal models (Wang et al, 2011b; Li et al, 2013b). More recently, a pilot study of tongue EIM was also completed (Shellikeri et al, 2015), in which an EIM electrode array was created by affixing four electrodes to a plastic tongue depressor wired directly to an impedance-measuring device. Significant differences could be detected between healthy individuals and those with ALS.…”