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Progression of hearing loss in experimental pneumococcal meningitis: correlation with cerebrospinal fluid
S M Bhatt1, A Lauretano, C Cabellos
1Department of Otology, Harvard Medical School, Massachusetts Eye & Ear Infirmary, Boston 02114.
Abstract:
The development of hearing loss and concomitant cerebrospinal fluid (CSF) cytochemical changes in a model of pneumococcal meningitis were examined. Rabbits were injected intracisternally with 10(5) pneumococci. Auditory evoked potentials to clicks and to 10- and 1-kHz tone bursts were recorded hourly; CSF was analyzed every 4 h. Sensorineural hearing loss developed in all animals beginning 12 h after infection and progressed to severe deafness. The onset of hearing loss was preceded by a CSF leukocytosis of > 2000 cells/microL and elevation of CSF protein and lactate concentrations to > or = 1 mg/mL. Temporal bone histopathology showed pneumococci and leukocytes extending from the CSF to the perilymph via the cochlear aqueduct. Hearing loss can develop early in the course of meningitis and is preceded by the abrupt onset of inflammatory changes in CSF. Progression of hearing loss is rapid and proceeds from cochlear base to apex in parallel with the degree of inflammation.
Insights
Pneumococcal meningitis rapidly causes severe sensorineural hearing loss in rabbits. This hearing impairment is linked to early cerebrospinal fluid (CSF) inflammation, including increased white blood cells and protein.
Area of Science:
- Otorhinolaryngology
- Neurology
- Infectious Diseases
Background:
- Pneumococcal meningitis is a serious infection that can lead to severe complications.
- Hearing loss is a known but poorly understood complication of meningitis.
Purpose of the Study:
- To investigate the development of hearing loss and associated cerebrospinal fluid (CSF) changes in a rabbit model of pneumococcal meningitis.
- To correlate auditory evoked potentials and CSF cytochemical alterations with histopathological findings.
Main Methods:
- Rabbits were intracisternally inoculated with Streptococcus pneumoniae.
- Auditory evoked potentials were recorded hourly, and CSF was analyzed every 4 hours.
- Temporal bone histopathology was performed to examine cochlear and CSF pathways.
Main Results:
- All rabbits developed sensorineural hearing loss starting 12 hours post-infection, progressing to severe deafness.
- The onset of hearing loss preceded by CSF leukocytosis (>2000 cells/µL), elevated protein, and lactate.
- Histopathology revealed pathogen and leukocyte migration from CSF to perilymph via the cochlear aqueduct.
Conclusions:
- Hearing loss can occur early in pneumococcal meningitis, preceding detectable auditory changes.
- Rapid inflammatory changes in CSF, including leukocytosis and increased protein/lactate, precede and correlate with hearing loss.
- Inflammation progression along the cochlear aqueduct contributes to the rapid, base-to-apex hearing loss observed.