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Electron microscopic temporal bone histopathology in experimental pneumococcal meningitis
J M Rappaport1, S M Bhatt, R S Kimura
1Department of Otolaryngology, Massachusetts Eye and Ear Infirmary, Harvard Medical School, Boston, USA.
Abstract:
Bacterial meningitis is one of the most common causes of acquired profound sensorineural deafness in children. Measurement of hearing and examination of the cochlea is limited in patients suffering from acute meningitis. A rabbit model of pneumococcal meningitis was developed to identify the temporal bone histopathologic changes that occur in meningogenic labyrinthitis caused by Streptococcus pneumoniae. Light microscopy was previously performed on temporal bones from acutely meningitic rabbits with profound hearing loss as determined electrophysiologically. Extensive inflammation of the cochlea with endolymphatic hydrops was observed. The organ of Corti, however, showed preserved architecture in the majority of these animals. In order to further investigate these findings, a protocol was used to create meningitic rabbits with hearing loss ranging from early high-frequency loss to profound deafness. The temporal bones from 7 rabbits were examined by transmission electron microscopy. In cases of mild hearing loss, partial degeneration of the inner row of outer hair cells, as well as edema of efferent cochlear nerve endings and marginal cells of the stria vascularis, was seen. With increasing degrees of hearing loss, the remainder of the organ of Corti and intermediate cells of the stria showed ultrastructural abnormalities. Spiral ganglion cells and basal cells of the stria vascularis remained intact in all subjects. This study provides unique information regarding the histology and pathophysiology of meningogenic deafness. The clinical implications of these findings are discussed, with an emphasis on potentially reversible changes and therapeutic intervention.
Insights
Bacterial meningitis can cause hearing loss in children. This study reveals early cochlear changes in a rabbit model, suggesting potential for reversible damage and therapeutic intervention.
Area of Science:
- Otolaryngology
- Neurology
- Pathology
Background:
- Bacterial meningitis is a leading cause of acquired sensorineural deafness in children.
- Assessing cochlear damage during acute meningitis is challenging.
- Streptococcus pneumoniae meningitis can lead to meningogenic labyrinthitis.
Purpose of the Study:
- To investigate temporal bone histopathology in a rabbit model of pneumococcal meningitis.
- To correlate hearing loss severity with cochlear ultrastructural changes.
- To explore potential for reversible damage and therapeutic strategies.
Main Methods:
- Developed a rabbit model of Streptococcus pneumoniae meningitis.
- Utilized electrophysiology to assess hearing loss.
- Examined temporal bones using light and transmission electron microscopy.
Main Results:
- Mild hearing loss showed outer hair cell degeneration and edema in cochlear nerve endings and stria vascularis.
- Severe hearing loss correlated with ultrastructural abnormalities in the organ of Corti and stria vascularis.
- Spiral ganglion cells and basal stria vascularis cells remained intact.
Conclusions:
- Early cochlear damage in bacterial meningitis involves specific cellular and ultrastructural changes.
- Findings suggest that some pathological changes may be reversible.
- This research provides insights into the pathophysiology of meningogenic deafness and potential therapeutic targets.