Embryological development and large vestibular aqueduct syndrome

Objectives/Hypothesis: Large vestibular aqueduct syndrome (LVAS) is a signi ficant cause of hearing loss in early childhood. Many theories on the origi ns and causes of LVAS have been proposed, including arrest or maldevelopmen t of the vestibular labyrinth in embryonic life, Prior studies have describ ed postnatal and adult vestibular aqueduct anatomy, but none has analyzed a queduct growth throughout embryonic life. This study was undertaken to char acterize the growth of the developing vestibular aqueduct to gain a better understanding of the possible origins of LVAS, Study Design: Basic science, temporal bone histopathological study, Methods: Serial sections from 48 te mporal bones from human embryos ranging in age from 5 weeks' gestation to f ull term were studied with computer image analysis. Measurements of vestibu lar aqueduct internal and external aperture, midportion diameter, and lengt h were analyzed to obtain a growth model of development. Results: The vesti bular aqueduct grows in a nonlinear fashion throughout embryonic Life, All parameters fit a similar growth curve and never reached a maximum or began narrowing during development, Growth in one parameter correlated well with growth of another. There was good side-to-side correlation with all but the external aperture. Conclusions: Most of the membranous labyrinth reaches a dult size by 20 weeks' gestation, but the vestibular aqueduct grows through out embryonic Life. The measurements and growth model obtained in this stud y are not consistent with the theory that LVAS results from an arrest in de velopment early in fetal life, The data suggest that LVAS may result from p ostnatal and early childhood maldevelopment.