We conducted a retrospective study to measure laryngeal descent in human infants and to determine if there is any correlation between the associated anatomic changes and the timing of the peak incidence of sudden infant death syndrome (SIDS), which is 2 to 4 months of age. We performed a computerized search of hospital records at our institution to identify magnetic resonance imaging (MRI) scans of the head and neck and plain radiographs of the lateral neck in patients younger than 1 year of age (range: 1 to 357 days). After unusable images were excluded, 79 head and neck MRI scans and 111 lateral neck x-rays were suitable for study. Two measurements were taken from each image: one from the tip of the epiglottis to the uvula and one from the tip of the epiglottis to the center of the sella turcica. These measurements were then graphed against the subject's age. SPSS statistical software was used to determine growth curves of the various measurements. The first derivative of these curves was calculated to determine the rate of laryngeal descent at a given age. We found that most subjects did not have an overlapping epiglottis and uvula during the first few months of life. The rate of laryngeal descent, based on measurements of the distance between the epiglottis and uvula, gradually increased in a near-linear fashion from as low as 0.005726 mm/day at day 1 of life to as high as 0.028366 mm/day at 300 days of age. We found no sharp increase in the rate of descent at 2 to 4 months of age, and thus no support for our hypothesis that there might be a correlation between anatomic changes and the peak incidence of SIDS.
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