An Improved Electrical Impedance Myography (EIM) Tongue Array for Use in Clinical Trials

Objectives: Electrical impedance myography (EIM) measurements of the tongue could provide valuable information about bulbar dysfunction in amyotrophic lateral sclerosis (ALS). A prototype tongue depressor EIM array produced gag reflexes. The objectives of this study were to determine the reliability, mean phase values, and tolerability of tongue EIM measurements using a smaller electrode array.

Methods: Tongue EIM measurements were performed in a total of 31 healthy individuals and four neuromuscular patients with lingual abnormalities. Reliability was assessed by calculating the intraclass correlation coefficient (ICC) and percent difference in addition to performing Bland-Altman analyses. Standard descriptive statistics, including results of a Mann-Whitney test, were also determined.

Results: At the 50 kHz frequency, the ICCs for intra- and inter-rater reliability were 0.76 with 5.17% difference and 0.78 with 5.34% difference respectively. The mean EIM phase values of healthy participants (11.61° ± 1.00°) and patients (9.87° ± 1.28°) were significantly different (p=0.0051). None of the participants experienced gag reflexes or discomfort.

Conclusions: The small tongue array provided good inter- and intra-rater reliability, could preliminarily distinguish between healthy and diseased muscle, and was well-tolerated.

Significance: Biomarker information about tongue health could be more comfortably obtained with a smaller EIM array.