The interarytenoid spatial relationship: accuracy and interrater reliability for determining sidedness in cases of unilateral adductor paresis

Background/objective: When adductor vocal fold paresis manifests without obvious motion impairment, identifying the paretic side can be challenging. Although increased vocal fold waveform amplitude ("floppiness") on videostroboscopy may be helpful, it has been shown to have low interrater reliability. We have found that the interarytenoid spatial relationship (IASR) can often accurately be used to predict the sidedness of electromyography (EMG)-determined unilateral adductor (thyroarytenoid/lateral cricoarytenoid [TA/LCA]) paresis. The goal of this study was to determine if a series of otolaryngology residents could learn to assess the IASR on videostroboscopy and use the IASR to identify the side of EMG-documented adductor paresis with high accuracy and interrater reliability.

Study design: Otolaryngology resident population surveys.

Methods: Ten residents were given videostroboscopy images on abduction/adduction from 10 consecutive patients with EMG-documented unilateral TA/LCA paresis and asked to identify the paretic side in a pretest. The IASR was then conceptually introduced to the otolaryngology residents in a brief presentation. Posttesting was then performed and used to assess EMG-based accuracy and interrater reliability.

Results: Before the IASR presentation, otolaryngology residents accurately identified the paretic side in 63% (95% confidence interval [CI]: 56-70%) of cases. In the posttest session, the residents accurately identified the paretic side in 93% (95% CI: 87-99%) of cases, and interrater reliability was 0.873.

Conclusions: The IASR may be useful in determining sidedness in cases of unilateral TA/LCA paresis. Further studies are needed to determine the sensitivity and specificity of the IASR for determining sidedness of unilateral TA/LCA paresis with intact mobility.