Imaging findings of the developing temporal bone in fetal specimens.

PURPOSE: To trace the development of the normal fetal temporal bone by means of plain radiography, MR, and CT. METHODS: Eighteen formalin-fixed fetal specimens, 13.5 to 24.4 weeks' gestational age, were examined with a mammographic plain film technique, CT, and MR imaging at 1.5 T. Temporal bone development and ossification were assessed. RESULTS: The membranous labyrinth grows with amazing rapidity and attains adult size by the middle of the gestation period. The cochlea, vestibule, and semicircular canals are very prominent and easily recognized on MR images. The otic capsule develops from a cartilage model. Ossification of the otic capsule proceeds rapidly between 18 and 24 weeks from multiple ossification centers that replace the cartilaginous framework. The mastoid, internal auditory canal, vestibular aqueduct, and external auditory canal continue to grow after birth. CONCLUSION: The study of fetal developmental anatomy may lead to a better understanding of congenital disorders of the ear. Faster MR scanning techniques may provide a method for in utero evaluation of the fetal temporal bone.

Postnatal development of the vestibular aqueduct in relation to the internal auditory canal. Computer-aided three-dimensional reconstruction and measurement study.

To investigate a possible developmental relationship between the internal auditory canal (IAC) and the vestibular aqueduct (VA), we made the following measurements in 10 normal temporal bones from individuals 4 months to 70 years of age at death, using a computer-aided three-dimensional reconstruction and measurement method: the volume of the VA, the length of the IAC, and the distance between the IAC and the external aperture of the VA. The degree of periaqueductal pneumatization was also assessed qualitatively by means of a light microscope. The three parameters increased postnatally in parallel with the development of the periaqueductal air cells, and all pairwise comparisons of these parameters showed a statistically significant correlation. Our results indicate that the IAC and VA develop synchronously and in parallel with the development of the periaqueductal air cells. We believe that an understanding of this relationship will be of help during surgery involving the IAC and VA, and may shed some light on the morphological features of Meniere's disease.

Dimensional anatomy of the vestibular aqueduct and the endolymphatic sac (rugose portion) in human temporal bones. Statistical analysis of 79 bones.

The purpose of this study was to investigate the anatomy of the vestibular aqueduct (VA) and rugose portion (RP) of the endolymphatic sac. Serial horizontal sections of 79 normal temporal bones of individuals aged 20 to 102 years were used. Medial view graphic reconstruction of the VA was performed for each specimen to determine the area, length, angle and position of the VA. The relationship between the width of the VA and the area of the VA, and the relationship between the degree of development of the VA and the degree of development of the temporal bone (periaqueductal pneumatization and the otic capsule in the periaqueductal region) were also investigated. Measurements of the RP were also made and further histological study of the RP was performed on 30 selected specimens. We found that 1) the VA in adult temporal bone varies in size and can be classified as hypoplastic, normoplastic, or hyperplastic; 2) many of the VAs in each group have similar sizes, although they vary in length, angle, or position; 3) all or most of the RP was located within the VA in all but one specimen, which had a hypoplastic VA (in this specimen more than half of the entire RP extended into the posterior cranial fossa); 4) the histology of the RP was characteristic in each type of VA; and 5) the degree of development of the VA seems to correlate with the degree of development of the otic capsule in the periaqueductal region.

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.

[Computed tomographic findings of the development of the bone around the vestibular aqueduct in Meniere's disease].

OBJECTIVE: To study the development of the bone around the vestibular aqueduct (VA) in Meniere's disease (MD) by CT. METHOD: The experiment consisted of three groups; normal ear group, non-MD vertigo group and MD group. VA in each group was examined by CT, and the minimum distance between the posterior semicircular canal and the posterior petrous surface where contain the endolymphatic sac. RESULT: VA visualization rate in MD was low, P-P distance in MD group was shorter than that of normal ear group and non-MD vertigo group. CONCLUSION: It is the fundamental pathological anatomy in MD that VA and the bone around VA are maldeveloped.