Otopathologic Analysis of Patterns of Postmeningitis Labyrinthitis Ossificans.

OBJECTIVE: Labyrinthitis ossificans (LO) may occur following meningitis and, in cases where cochlear implantation is indicated, complicate electrode insertion. LO is critical to identify for successful cochlear implantation, and histopathology is more sensitive than imaging for identification of LO. Herein we utilize otopathologic techniques to study the timing and location of intracochlear tissue formation following meningitic labyrinthitis (ML). STUDY DESIGN: Retrospective review. SETTING: Academic institution. METHODS: Temporal bone specimens with a history of bacterial ML were histologically evaluated. The location and extent of intracochlear tissue formation within the scala tympani (ST) and scala vestibuli (SV) were graded, and spiral ganglion neurons were counted. RESULTS: Fifty-one temporal bones were identified: 32 with no intracochlear tissue formation, 9 with fibrosis alone, and 10 with LO. Fibrosis was identified as early as 1.5 weeks after ML, while ossification was found only in specimens that survived multiple years after ML. All LO cases showed ossification of the ST at the round window membrane (RWM) with continuous extension throughout the basal turn. Extent of SV ossification correlated with that in the ST but showed frequent isolated distal involvement of the cochlea. Spiral ganglion neuron counts were lower than those in age-matched controls. CONCLUSION: In this human temporal bone study, we found that postmeningitic LO results in ossification at the RWM with continuous extension into the ST of the basal turn and variable involvement of the SV. Identification of a patent basal turn beyond RWM ossification of the ST should permit full electrode insertion. LEVEL OF EVIDENCE: Retrospective review.

Ototoxicity resulting from intracochlear perfusion of Streptococcus pneumoniae in the guinea pig is modified by cefotaxime or amoxycillin pretreatment.

Acute changes in the electrophysiology and ultrastructure of the organ of Corti were studied after microperfusion of c. 5 x 10(6) CFU of serotype 2 Streptococcus pneumoniae D39 or Escherichia coli K-12 directly into the scala tympani of guinea pigs. Hearing loss was assessed by recording the auditory nerve compound action potential response to a 10 kHz tone pip. Mean hearing loss 3 h after pneumococcal perfusion (n = 4) was 44 dB, compared to 6 dB after E. coli perfusion (n = 4) (P<0.001). After pneumococcal perfusion, scanning electron microscopy revealed damage to hair cell stereocilia and cratering of the apical surface of supporting cells. Intraperitoneal injection of 100 mg/kg cefotaxime (n = 4) or 100 mg/kg amoxycillin (n = 4) 30 min before perfusion of pneumococci significantly reduced mean hearing loss to 23 dB (P=0.01) or 20 dB (P=0.01), respectively, and diminished ultrastructural damage. The data suggest that if pneumococci invade the inner ear during meningitis, cochlear deafness may rapidly ensue.

Acute measles infection in the hamster cochlea.

Measles virus has been implicated in sudden sensorineural hearing loss (SNHL) in adults as well as in children. Furthermore, sensorineural hearing loss following live measles virus vaccination has been reported. As of yet, however, there has been only few reports on human temporal bone pathology due to measles, and on experimental animal models of measles infection. This study was undertaken to examine acute measles infection in adult hamster cochlea morphologically and immunohistochemically for precise understanding of this viral infection. Atrophy of the stria vascularis, loss of the organ of Corti, "rolled-up" tectorial membrane, and cell infiltration with a positive immunofluorescent reaction primarily within the scale media indicating endolymphatic labyrinthitis were the principal findings. These results were generally consistent with previous ones on human temporal bone pathology not only due to measles but also to SNHL. We consider measles virus to be one of the possible pathogens, even if low in frequency, causing profound and irreversible hearing loss, including SNHL. Completion of measles vaccination without complication and selective or mass revaccination may be necessary to prevent such hearing loss.

Spiral modiolar vein: its importance in viral load of the inner ear.

Guinea pig-specific cytomegalovirus and Sendai virus were inoculated into the cochleas of seronegative guinea pigs to study the route of entry of cells participating in inner ear inflammation. Inflammatory cells accumulated around the spiral modiolar vein and appeared to be streaming from this vein into the scala tympani via a collecting venule. Inactivated virus inoculated into the cochlea and normal control cochlea failed to show inflammatory cell infiltrates. The spiral modiolar vein appears to play an important role in the movement of cells from the systemic circulation into the inner ear as part of the host's normal defense against invading pathogens such as viruses.