Later stages of development of the periotic duct and its adjacent area in the human fetus

Abstract

The later stages of development (16–40 weeks in utero) of the periotic duct and its adjacent areas in the human fetus indicate that the critical stages of development occur in four specific time related stages over a six‐week period (20–26 weeks). First, the petrous apex ossifies to separate the inferior cochlear vein into the canal of Cotugno and forms the medial wall of the cochlear aqueduct (22 weeks); second, the canalicular otic capsule fuses with the cochlear otic capsule to obliterate Hyrtl fissure and forms the lateral wall of the cochlear aqueduct (24 weeks); third, progressive bone deposition to the medial surface of the membranous labyrinth and cochlea at the petrous apex elongates the periotic duct and cochlear aqueduct (32 weeks in utero); and fourth, active arachnoid tissue ingrowth into the periotic duct occurs at 20–24 weeks and 34–40 weeks in utero. The terminal event is widening of the CNS opening of the periotic duct at 32 weeks in utero. The periotic duct and cochlear aqueduct length increase with gestation from 26 weeks until term. The periotic duct width remains the same throughout the gestation. The cochlear aqueduct width diminishes with gestational age. The periotic duct remains patent throughout 16‐40 weeks in utero.

The cochlear aqueduct in pediatric temporal bones

“…There was some variability seen, but unfortunately gestational ages were not reported. Our measurements fill in the informational gap between the lengths of the cochlear aqueduct in the fetus as measured by Spector et al [24] and measurements in adults by Rask-Andersen et al…”

“…At first the cochlear aqueduct is straight, but with progressive ossification and expansion of the otic capsule, it elongates and becomes curved. Spector et al [24] found that from 32 weeks of gestational age to 1 day postpartum there was an increase in the diameter of the external und internal aperture of the aqueduct with development of a funnel-shaped appearance. We also observed this change in our material.…”

“…Early pathologists such as Retzius [21] and later Karlefors [9] studied the patency of the aqueduct by injecting dye, but these techniques were relatively unphysiological. In eight previously reported histopathological studies the cochlear aqueduct was measured in fetuses, infants and adults [2,9,12,13,15,17,18,20,22,24].…”

“…In a histological study of the later stages of development in the human fetus, Spector et al [24] found a progressive deposition of bone on the medial surface of the labyrinth which resulted in elongation and narrowing of the cochlear aqueduct. This lengthening seemed to continue with postnatal growth.…”

“…A P level below 0.05 was considered to be significant. All results were compared to previously reported measurements of the human cochlear aqueduct [2,9,12,13,15,17,18,20,22,24].…”