New aspects in the histopathology of the cochlear aqueduct in children

Abstract

Objective: To study the histoanatomy and pattern of growth of the cochlear aqueduct in children of different ages.

Background: Since Du Verney described the cochlear aqueduct in 1684, its form, pattern of growth, patency, and function have been controversial. As most of the previous studies of the aqueduct were performed on adults, none had looked at its pattern of growth from the neonate to 9 years of age. In addition, previous histologic studies had suggested an age-dependent patency, but recent investigations had not statistically correlated patency with age.

Method: Histologic sections of 137 temporal bones from 79 infants and children were studied by light microscopy. From this group, we selected 32 temporal bones from 18 infants, newborn to 9 years (average age 9.1 months, median 0.5 months), in whom the entire length of the cochlear aqueduct was visible on one histologic section. We measured the width of the orifices at the scala tympani (external aperture) and the subarachnoid space (internal aperture) and the length of the aqueduct, and noted the contents of the lumen.

Results: The measurements of the cochlear aqueduct were: length 4.19 mm (range 1.7-10.7 mm), width of the external aperture 435 microm (range 225-869 microm), width of the internal aperture 1,323 microm (range 699-2344 microm), mean diameter of the narrowest part (isthmus) 138 microm (range 68-244 microm), intraluminal mononucleated cells 6%, and erythrocytes 15%.

Conclusions: Our findings demonstrate that, in the newborn, the cochlear aqueduct is short and patent. After birth, the duct lengthens significantly primarily by growth of the medial periosteal portion. There was no statistically significant change in the diameter of the external and internal apertures and the isthmus with age. With one exception, the cochlear aqueduct was always present and patent.