Development of the orohypopharyngeal cavity in normal infants and young children.

OBJECTIVE: To study the growth of the oropharynx and hypopharynx in infants and young children by measuring the lengths of the segments between nasopharyngeal valve and tongue base, tongue base and arytenoids, and arytenoids and upper esophageal sphincter. These measurements will be used as references for developing manofluoroscopy to study deglutition in infants and young children. PATIENTS AND METHODS: Twenty-three children (14 boys, 9 girls) between birth and 4 years of age were prospectively studied. All children had near normal growth parameters and were free of medical illnesses or other major medical conditions that are known to influence the pharyngeal cavity. Lateral videofluoroscopy was used to assess the pharyngeal structures during breathing. All images were digitally recorded and analyzed using a computer program designed specifically for this study. RESULTS AND CONCLUSIONS: Statistically significant correlations were found between the age or height of the patient and the distance from velopharyngeal valve to tongue base and the distance from tongue base to arytenoids, showing a linear increase of the length of the oro- and hypopharynx with age and patient height. There was no significant difference in the pharyngeal distances between boys and girls. On the basis of these results, a linear regression comparison could be established to define the length of each pharyngeal segment for any age until 4 years and for the 50th percentile of height.

Androgen stimulation and laryngeal development.

Androgen-induced changes in laryngeal growth patterns were studied using a sheep animal model. Forty-eight lambs were divided into eight treatment groups. Lambs in seven of the groups were castrated at birth, while lambs in the eighth group served as an intact (noncastrated) control. Six groups were then treated with varying doses of testosterone and dihydrotestosterone, while the seventh served as a castrated, nontreated control. All animals were killed and gross dissections of the larynges were performed. Thirty-four linear and angular measurements were obtained from each larynx. The mean superior thyroid horn separation showed the most dramatic androgen-induced effect (p = 0.023). Laryngeal anterior-posterior diameter, superior thyroid horn height, posterior thyroid cartilage width, thyroid cartilage angle, and vocal process to arytenoid base distances all demonstrated positive dose-response relationships. Hypoandrogenic levels appeared to have an inhibitory effect upon laryngeal growth when compared to castrated controls.