Abnormalities of the Neonatal Ear: Otoscopic Observations, Histologic Observations, and a Model for Contamination of the Middle Ear by Cellular Contents of Amniotic Fluid
Authors: Eavey Roland D. 
Published: February 2017

It is unknown whether childhood ear disease could be present long before symptoms provoke an initial otoscopic examination. A newborn middle ear might or might not start in a pristine, privileged state. The clinician evaluating later infant and childhood ear disease is often unaware of the status of a patient's ear from the neonatal period, the earliest time at which the tympanic membrane can be evaluated. Adding to the physician's handicap, normative otoscopic and histologic data on the neonatal ear are incomplete. In order to test the hypothesis that disease in the neonatal middle ear may be more common than is generally appreciated, the population of critically ill neonates was selected for study since this group can provide both clinical as well as histologic data.

This manuscript is divided into three parts. Clinically, otoscopic observations were analyzed on infants in an intensive care unit. Histologically, neonatal temporal bones were studied for normal anatomy and pathology of the middle ear and antrum. Experimentally, an animal study was performed to evaluate the potential effect of amniotic fluid cellular contents aspirated into the middle ear.

I. Clinical Otoscopic Observations. Daily otoscopic examination was conducted on 44 neonates in an intensive care unit. Specific parameters of the otoscopic examination were evaluated to compare with the normal, translucent tympanic membrane of the older child. The otoscopic appearance was found to be abnormal in 97. 7% of neonatal ears. Of the otoscopic parameters evaluated, right ears averaged 2.6 abnormalities and left ears averaged 2.5 otoscopic abnormalities. The otoscopic appearance of the neonate in the neonatal intensive care unit is nearly universally abnormal.

II. Temporal Bone Histologic Observations. One hundred eleven temporal bones from 56 neonates were collected for histologic study by light microscopy. Mesenchyme filling more than 60% of the middle ear space was found in 13 bones. Amniotic fluid cellular content was detected in 90 bones. Purulent otitis media was detected in 24 bones. Varying amounts of blood were found in the middle ear space of 34 bones. Only 7 of the bones had no significant middle ear abnormality. It is concluded that in the critically ill neonate, the middle ear and antrum usually contain cellular or fluid material, often in significant volume, that would not be considered normal in the older patient.

III. An Animal Model Simulating Contamination of the Middle Ear by Cellular Contents of Amniotic Fluid. In human neonatal ears the histologic residue of refluxed amniotic fluid, keratinized epithelial cells and lanugo hair, initiates a foreign‐body giant‐cell reaction with granulation tissue formation. It was hypothesized that this residue might not be evacuated easily and potentially could persist as an inflammatory nidus. An animal model· was designed to determine if the human findings could be reproduced and to analyze the host reaction over 2 months. An aliquot of autologous, sterilized hair and keratinized epithelial cells was placed into the left hulla of seven gerbils. The contralateral bulla underwent saline instillation as a control. The animals were killed from time 0 to 63 days. By 1 week, the experimental ear with keratin demonstrated not only hair but angioneogenesis with granulation tissue, blood, and proteinaceous precipitate. This pattern persisted so that at 63 days the keratinized cellular elements were still present. In addition, further pathologic changes including osteoneogenesis and cholesterol granuloma were found. Control ears were unremarkable. It is concluded that the foreign‐body reaction provoked by autologous keratin in this model provided histologic findings similar to that seen in the human neonatal temporal bones and that, by 2 months, this material had not been eliminated but was still producing a foreign‐body reaction.

These studies demonstrate that the otoscopic appearance of the critically ill neonate is distinct from the typical tympanic membrane appearance of the older child, that the ear is subject to several significant pathologic conditions, and that such pa· thology might not spontaneously and quickly improve. Therefore, vigilant otologic attention is war· ranted even for the youngest patients.