Postnatal development of the vestibular aqueduct and endolymphatic sac.

The purpose of this study was to gain basic information about the postnatal development of the vestibular aqueduct (VA) and the endolymphatic sac (ES). For this study, serial horizontal sections of 31 normal temporal bones of individuals whose ages ranged from 0 to 13 years were used. Medial view graphic reconstruction of the VA and rugose portion (RP) of the ES was performed in every case for analysis of the VA and RP. The findings of this study revealed the following new information about the postnatal development of the VA and ES. 1) The VA and RP undergo significant growth postnatally up to age 3 years. 2) In the newborn, individual variations in the VA and RP already exist and at age 3 years significantly wide individual variations which can be classified into three groups (hypoplastic, normoplastic, hyperplastic) may be recognized. 3) Hypoplastic VAs are of two types: one is fairly elongated and tubelike while the other is short and funnel-shaped. The tubelike VA seems to be the prenatal form. 4) The changes that occur with development postnatally in the area of the VA are more closely related to the changes that occur in the length of the external aperture of the VA than they are to the changes that occur in the length of the VA. 5) Development of the area of the VA is closely correlated with development of the area of the RP.