Role of ultrasound in the assessment of vocal cord function in infants and children.

The determination of the cause of stridor in the infant and child is an important directive for the otolaryngologist. The limitations of current clinical diagnostic techniques have provided the impetus for pursuing newer, more practical techniques to diagnose vocal cord paralysis in children. The purpose of this paper is to describe a new technique to image the larynx and determine its role in discerning vocal cord paralysis in children. This study began with an animal study (lamb model) demonstrating that computerized ultrasound can accurately delineate laryngeal anatomy and function. The human protocol included 27 patients (age 1 day to 14 years): 15 with normal larynges and 12 with vocal cord paralysis. Recorded ultrasound studies of these subjects were compiled in a randomly ordered videotape and presented twice and viewed in a blinded manner by four expert raters. Statistical analysis of their readings revealed that ultrasound is a highly accurate technique to document vocal cord paralysis, with a high degree of interrater and intrarater reliability. Beyond the accuracy and consistency of computerized ultrasound, there are many other aspects of this technique that make it clinically attractive. Laryngeal ultrasound is noninvasive, painless, and widely accepted. It is relatively safe, with no radiation exposure and no need for sedation or anesthesia. It is well tolerated by patients and their families. The results are easily displayed and recorded and available for hard copy storage. This investigation should not be interpreted as an endorsement for laryngeal ultrasound as a replacement for endoscopy in children. This work does indicate, however, that ultrasound is a technique that can accurately address the special issue of vocal cord mobility in infants and children. At present, this is the primary use for laryngeal ultrasound, although with additional investigation and sophistication it is likely that ultrasound of the larynx may become useful for other purposes.