Chronology of labyrinthitis ossificans induced by Streptococcus pneumoniae meningitis

Pneumococcal Meningitis Induces Hearing Loss and Cochlear Ossification Modulated by Chemokine Receptors CX3CR1 and CCR2

PURPOSE

Pneumococcal meningitis is a major cause of hearing loss and permanent neurological impairment despite widely available antimicrobial therapies to control infection. Methods to improve hearing outcomes for those who survive bacterial meningitis remains elusive. We used a mouse model of pneumococcal meningitis to evaluate the impact of mononuclear phagocytes on hearing outcomes and cochlear ossification by altering the expression of CX3CR1 and CCR2 in these infected mice.

METHODS

We induced pneumococcal meningitis in approximately 500 C57Bl6 adult mice using live Streptococcus pneumoniae (serotype 3, 1 × 105 colony forming units (cfu) in 10 µl) injected directly into the cisterna magna of anesthetized mice and treated these mice with ceftriaxone daily until recovered. We evaluated hearing thresholds over time, characterized the cochlear inflammatory response, and quantified the amount of new bone formation during meningitis recovery. We used microcomputed tomography (microCT) scans to quantify cochlear volume loss caused by neo-ossification. We also performed perilymph sampling in live mice to assess the integrity of the blood-perilymph barrier during various time intervals after meningitis. We then evaluated the effect of CX3CR1 or CCR2 deletion in meningitis symptoms, hearing loss, macrophage/monocyte recruitment, neo-ossification, and blood labyrinth barrier function.

RESULTS

Sixty percent of mice with pneumococcal meningitis developed hearing loss. Cochlear fibrosis could be detected within 4 days of infection, and neo-ossification by 14 days. Loss of spiral ganglion neurons was common, and inner ear anatomy was distorted by scarring caused by new soft tissue and bone deposited within the scalae. The blood-perilymph barrier was disrupted at 3 days post infection (DPI) and was restored by seven DPI. Both CCR2 and CX3CR1 monocytes and macrophages were present in the cochlea in large numbers after infection. Neither chemokine receptor was necessary for the induction of hearing loss, cochlear fibrosis, ossification, or disruption of the blood-perilymph barrier. CCR2 knockout (KO) mice suffered the most severe hearing loss. CX3CR1 KO mice demonstrated an intermediate phenotype with greater susceptibility to hearing loss compared to control mice. Elimination of CX3CR1 mononuclear phagocytes during the first 2 weeks after meningitis in CX3CR1-DTR transgenic mice did not protect mice from any of the systemic or hearing sequelae of pneumococcal meningitis.

CONCLUSIONS

Pneumococcal meningitis can have devastating effects on cochlear structure and function, although not all mice experienced hearing loss or cochlear damage. Meningitis can result in rapid progression of hearing loss with fibrosis starting at four DPI and ossification within 2 weeks of infection detectable by light microscopy. The inflammatory response to bacterial meningitis is robust and can affect all three scalae. Our results suggest that CCR2 may assist in controlling infection and maintaining cochlear patency, as CCR2 knockout mice experienced more severe disease, more rapid hearing loss, and more advanced cochlear ossification after pneumococcal meningitis. CX3CR1 also may play an important role in the maintenance of cochlear patency.

Protocol for Evaluation and Management of Hearing Loss After Meningitis

Bacterial meningitis is the most common cause of post-natal acquired hearing loss in children. Although cochlear implantation helps in improving the hearing in these patients, the fibrosis and ossification of the cochlear lumen that occurs as a result of bacterial meningitis, limits the chances of successful implantation. In developing countries like India, the reduced awareness, limited resources, and financial constraints warrant judicial use of radiological and audiological tests to increase the rate of successful cochlear implantation. The present paper is a review of the literature and a proposed protocol for follow-up of post-meningitis patients to help clinicians diagnose and hence, intervene early when profound hearing loss occurs. Every patient who has had an episode of bacterial meningitis must be followed up for atleast 2 years for possible hearing loss with frequent audiological and radiological evaluation, as required. Cochlear implantation must be done as early as possible when profound hearing loss is detected.

Cochlear implantation for post-meningitis deafness with cochlear ossification: diagnosis and surgical strategy

BACKGROUND

Cochlear ossification (CO) after meningitis can cause profound sensorineural hearing loss (SNHL). Cochlear implantation (CI) is the ideal treatment strategy for CO.

AIMS

To explore the strategy for CI in patients with CO after meningitis.

MATERIALS AND METHODS

In this retrospective study, the medical records of patients diagnosed with profound SNHL due to CO after meningitis and who underwent CI in our department between September 2010 and September 2021 were collected and reviewed. Their imaging and surgical findings were analyzed.

RESULTS

The data of 26 patients with unilateral CI were reviewed. All patients underwent preoperative temporal high-resolution computed tomography (HRCT) and 22 patients magnetic resonance imaging (MRI). The sensitivity of HRCT was 61.5% (10/26), whereas that of MRI was 81.8% (18/22). Combined HRCT and MRI achieved a detection rate of 92.3% (24/26). Twenty-two and four patients underwent complete and partial electrode implantations, respectively.

CONCLUSIONS AND SIGNIFICANCE

Preoperative temporal bone HRCT and MRI are essential for determining whether a patient is suitable for CI and surgical planning. A false-negative diagnosis is possible when diagnosing CO, but combined HRCT and MRI can improve the positive rate of preoperative diagnosis of CO post meningitis. Early CI is recommended.

Cochlear implantation after deafness from Pasteurella multocida meningitis

A woman in her late 40s who works as a veterinary technician represented to the emergency department with increasing headache, confusion, neck stiffness, subjective fevers and distorted hearing 2 days after diagnosis of viral infection at an outside emergency department.Diagnosis of Pasteurella multocida was made from blood cultures and lumbar puncture. Intravenous ceftriaxone was administered for 21 days. By the time of resolution of acute meningitis, she had become completely deaf bilaterally. MRI revealed faint early ossification/possible labyrinthitis ossificans of the basal cochlea, which was confirmed on surgical exploration during the placement of cochlear implants bilaterally 42 days later. We discuss how the atypical features of this infection lead to diagnostic delay and high morbidity, the unique imaging/surgical findings resulting from the infection, and the clinical utility of early and bilateral cochlear implantation in this and similar cases.

Revision cochlear implantation using a double array device in the post-meningitis ossified cochlea

PURPOSE

To describe the surgical technique and outcome in a series of patients who underwent revision cochlear implantation using a double array or split electrode device. All patients developed ossified cochleae due to meningitis and were functioning poorly with the previous implant.

METHODS

Four patients between the ages of 4-15 years underwent revision with five double-array cochlear implant devices. One patient underwent bilateral revision surgery. All patients had previous meningitis with CT and MRI imaging studies that demonstrated completely ossified cochleae. The time interval range between the disease and the initial cochlear implantation and was 4 months to 3 years. The patient's data were retrospectively analyzed with emphasis on the surgical technique, the number of electrodes inserted, and the number of active electrodes at follow-up. In addition, pre and post-revision surgery function was compared.

RESULTS

The revision surgery was carried out 2-11 years after the initial surgery. Two tunnels, basal and apical, were drilled in the ossified cochlea. In each of the tunnels, 5 to 11 electrodes were inserted. While the number of active electrodes before revision was 0-5, after revision with the double array, it was increased to 8-12, resulting in improved auditory and speech function.

CONCLUSION

Revision cochlear implantation with a double array implant using the two tunnel technique can increase the number of active electrodes. This leads to a better outcome in post-meningitis children with completely ossified cochleae and a poor functioning previous device.

Histopathological changes to the peripheral vestibular system following meningitic labyrinthitis

OBJECTIVE

While cochlear ossification is a common sequalae of meningitic labyrinthitis, less is known about the effects of meningitis on peripheral vestibular end organs. Herein, we investigate histopathologic changes in the peripheral vestibular system and cochlea in patients with a history of meningitic labyrinthitis.

METHODS

Temporal bone (TB) specimens from patients with a history of meningitis were evaluated and compared to age-matched controls. Specimens were evaluated by light microscopy and assessed for qualitative changes, including the presence of vestibular and/or cochlear endolymphatic hydrops, presence and location of inflammatory cells, new bone formation, and labyrinthitis ossificans; and quantitative changes, including Scarpa's ganglion neuron (ScGN) and spiral ganglion neuron (SGN) counts.

RESULTS

Fifteen TB from 10 individuals met inclusion and exclusion criteria. Presence of inflammatory cells and fibrous tissue was found in 5 TB. Of these, evidence of labyrinthitis ossificans was found in 2 TB. In the peripheral vestibular system, mild to severe degeneration of the vestibular membranous labyrinth was identified in 60% of cases (n = 9 TBs). There was a 21.2% decrease (range, 3%-64%) in the mean total count of ScGN in patients with meningitis, compared to age-matched controls. In the cochlea, there was a 45% decrease (range, 25.3%-80.9%) in the mean total count of SGN compared to age-matched controls (n = 14 TBs).

CONCLUSIONS

Otopathologic analysis of TB from patients with a history of meningitic labyrinthitis demonstrated distinct peripheral vestibular changes. Future research may help to delineate potential mechanisms for the observed otopathologic changes following meningitis.

LEVEL OF EVIDENCE

N/A.

Terrible Twos or Early Signs of Psychopathology? Developmental Patterns in Early Identified Preschoolers With Cochlear Implants Compared With Hearing Controls

OBJECTIVE

Cochlear implants (CIs) have dramatically improved the lives of children who are deaf or hard of hearing; however, little is known about its implications for preventing the development of psychiatric symptoms in this at-risk population. This is the first longitudinal study to examine the early manifestation of emotional and behavioral disorders and associated risk and protective factors in early identified preschoolers with CIs compared with hearing peers.

DESIGN

Participants were 74 children with CIs and 190 hearing controls between ages 1 and 5 years (mean age, 3.8 years). Hearing loss was detected using the Newborn Hearing Screening in The Netherlands and Flanders. Parents completed the Early Childhood Inventory-4, a well-validated measure, to evaluate the symptoms of DSM-IV-defined psychiatric disorders, during three consecutive years. Language scores were derived from each child's medical notes.

RESULTS

Children with CIs and hearing controls evidenced comparable levels of disruptive behavior and anxiety/depression (which increased with age in both groups). Greater proficiency in language skills was associated with lower levels of psychopathology. Early CI and longer duration of CI use resulted in better language development. In turn, higher early language skills served as a protective factor against the development of disruptive behavior symptoms.

CONCLUSIONS

This longitudinal study uniquely shows that improvement in language skills mitigates the development of early signs of psychopathology. Early identification of hearing loss and CIs help children improve their language skills.

Labyrinthitis Ossificans in a Cynomolgus Macaque (Macaca fascicularis)

Labyrinthitis is inflammation of the membranous and bony labyrinth of the inner ear. Typical portals of entry includehematogenous spread from the cochlear vasculature, passage of otitis media pathogens through the round window, and mostcommonly, meningogenic spread from the subarachnoid space. The sequela of chronic inner ear inflammation is labyrinthitisossificans, in which inner ear structures are replaced by fibrous and osseous tissues. Labyrinthitis in humans has been reportedconcurrently with infection due to various viruses (for example, varicella-zoster, measles, mumps) and bacteria (for example,Treponema pallidum, Streptococcus pneumoniae) and may be associated with vertebrobasilar ischemia and meningitis. Profoundsensorineural hearing loss is a common, serious complication of this disease. Here, we report a case of labyrinthitisossificans in a cynomolgus macaque (Macaca fascicularis) with a potential infectious etiology. Historically, this animal hadan indwelling femoral intravenous catheter for more than 4 y. He presented with a right-sided head tilt and incoordinationof 2 mo duration. The macaque was treated with NSAID and antibiotics, which corrected the incoordination but not the headtilt. MRI revealed right-sided labyrinthitis, and euthanasia was elected due to clinical signs that were refractory to treatment.Gross pathology was unremarkable, but histopathology revealed chronic labyrinthitis ossificans with local fibroplasia andvestibuloauditory neuritis. We describe here the clinical features, imaging, and histologic lesions of labyrinthitis in a macaque.

Deterioration of Vestibular Cells in Labyrinthitis

OBJECTIVE

To quantitatively assess the effect of serous labyrinthitis, suppurative labyrinthitis, and labyrinthitis ossificans on vestibular hair cells, dark cells, and transitional cells.

METHODS

We examined human temporal bone specimens with serous labyrinthitis, suppurative labyrinthitis, and labyrinthitis ossificans, then compared them with age-matched control groups without labyrinthitis. We evaluated the density of type I and II vestibular hair cells, dark cells, and transitional cells in the peripheral sensorial organs.

RESULTS

The mean density of type I vestibular hair cells in the maculae of the saccule significantly differed between the serous labyrinthitis group and its control group. The loss of type I and II vestibular hair cells in all of the peripheral sensorial organs was significantly higher in the suppurative labyrinthitis group than in its control group. The mean density of dark cells in the lateral and posterior semicircular canals was significantly lower in the suppurative labyrinthitis group than in its control group. The mean density of type I and II vestibular hair cells, dark cells, and transitional cells was significantly lower in the labyrinthitis ossificans group than in its control group.

CONCLUSION

The loss of vestibular hair cells and degenerative changes in dark cells and transitional cells could affect vestibular function in patients with labyrinthitis.

Inhibition of Post-Meningitic Cochlear Injury with Cerebrospinal Fluid Irrigation

OBJECTIVE: Labyrinthitis ossificans, the pathologic ossification of the otic capsule associated with profound deafness and loss of vestibular function occurs frequently as a sequella of bacterial meningitis and subsequent purulent labyrinthitis. Experimentally, in Streptococcus pneumoniae meningitis, it has been shown that a vigorous inflammatory response to teichoic acids in the bacterial cell wall contributes to cochlear damage and subsequent fibrosis and ossification. The hypothesis of this study is that a dilution of concentration of inflammatory mediators through cerebrospinal fluid (CSF) irrigation will lead to a reduction in both inner ear pathology and permanent hearing loss.

STUDY DESIGN AND SETTING: Auditory brainstem response testing was used to determine baseline hearing thresholds in 20 Mongolian gerbils (12 irrigated, 8 sham irrigated animals) at 32 kHz, 16 kHz, 8 kHz, and 4 kHz frequencies. Their thresholds at 14 days and 120 days post-procedure were also obtained. Streptococcus pneumoniae meningitis was induced in both groups of animals by intrathecal (i.t.) injection of bacteria. Both groups received penicillin treatment. Forty-eight hours after inoculation, both groups were implanted with i.t. inflow and outflow catheters. The irrigated group was infused continuously with artificial CSF over 36 hr at a rate of 70 μL/hr and the outflow sampled. The tubing in the sham irrigated group was clamped (without sampling). They were sacrificed at 120 days post-procedure and histomorphometric analysis carried out. The concentration of interleukin 1β (IL-1β) for the CSF samples from the irrigated group were compared to samples collected from an additional control group of 8 non-irrigated meningitic gerbils. IL-1β was chosen to study because it is a potent pro-inflammatory cytokines in bacterial meningitis that is unaffected by the neurosurgical trauma of the experimental protocol.

RESULTS: Twenty animals survived the meningitis (6 irrigation, 6 sham irrigation, 8 non-irrigation meningitic controls). At Days 14 and 120 post-infection, the irrigated animals manifested significantly less hearing loss with a mean loss of 28.82 dB compared to the sham irrigation group mean loss of 40.76 dB ( P < 0.03). The degree of hearing loss in both groups was frequency-dependent with greater loss at higher frequencies (mean loss = 22.4 dB at 32 kHz, 23.0 dB at 16 kHz, 18.6 dB at 8 kHz, and 12.5 dB at 4 kHz). Histomorphometric analysis demonstrated a marked reduction in degeneration of the spiral ligament, spiral ganglion cells, and stria vascularis in experimental animals as compared to controls. Immunohistochemistry showed a significant reduction in IL-β1 concentrations in the irrigated animals compared to the non-irrigated, infected controls ( P < 0.03).

CONCLUSIONS: Irrigation of CSF resulted in a significant reduction in post-meningitic cochlear injury when compared to controls. This model for continuous cerebrospinal fluid irrigation provides a means to evaluate the effects of a dilution of inflammatory mediators on hearing loss and labyrinthitis ossificans after bacterial meningitis.

SIGNIFICANCE: Despite advances in the prevention of meningitis and improved antibiotic treatment, bacterial meningitis continues to have significant associated morbidity. This study provides insight into some of the mechanisms responsible for post-meningitic hearing loss and labyrinthitis ossificans and presents a novel approach to reduce these complications.

EBM rating: C-4

Bacterial invasion of the inner ear in association with pneumococcal meningitis

OBJECTIVE

To examine the pathways of bacterial invasion and subsequent spreading in the inner ear during pneumococcal meningitis.

STUDY DESIGN

A well-established adult rat model of Streptococcus pneumoniae meningitis was used.

METHODS

Thirty rats were inoculated intrathecally with S. pneumoniae serotype 1, 3 or 9 V and received no additional treatment. The rats were sacrificed when reaching terminal illness or on Day 7 and then prepared for serial sectioning and PAS-Alcian blue staining for light microscopy.

RESULTS

During the first few days after inoculation, bacteria invade the inner ear through the cochlear aqueduct, into the scala tympani of the cochlea (perilymphatic space). From here, bacteria spreads apically toward the helicotrema and subsequently basally through the scala vestibuli, toward the vestibule and the vestibular system. When the bacteria after 5 to 6 days had reached scala vestibuli of the basal turn of the cochlea, hematogenous spreading occurred to the spiral ligament and into the cochlear endolymph, subsequently to the vestibular endolymph. We found no evidence of alternative routes for bacterial invasion in the inner ear. Several internal barriers to bacterial spreading were found within the inner ear. Bacterial elimination was evidenced by engulfment by macrophages within the inner ear.

CONCLUSION

From the meninges, pneumococci invade the inner ear through the cochlear aqueduct during the first days of infection, whereas hematogenous invasion via the spiral ligament capillary bed occur at later stages. Although internal barriers exist within the inner ear, the spreading of bacteria occurs via the natural pathways of the fluid compartments. Bacterial elimination occurs by local macrophage engulfment.

Our experience with split electrode array implant for obliterated cochlea

To study the outcomes of split electrode array cochlear implantation in ossified cochlea using the CAP scoring system. Retrospective case study. Tertiary referral center. Six cochleae in three adult and three pediatric patients with ossification.

INTERVENTION(S)

All Patients underwent cochlear implantation with a split electrode array system. Major outcome parameter(s): Number of electrodes inserted during surgery, number of functioning electrodes on follow-up and auditory performance evaluation using the CAP score-Category of Auditory Perception [TSC Revised Version, based on Nottingham CI Program, 1995]. Six patients (three children and three adults) had insertion of split electrode array system. The mean number of electrodes inserted were 18.3 (range 15-21) and functioning electrodes at follow-up were mean of 14.3 (range 7-21). Auditory performance was measured using CAP score at 1 year post implant follow up, mean score in children was six and that in adult was eight. One pt had facial nerve twitching which was corrected by switching off the concerned electrode. No complications in sort of facial palsy or vestibular disorder were observed. Patients of ossified cochlea having profound deafness do well with split electrode array cochlear implantation as evaluated with CAP scoring system. The split electrode array results in more number of electrodes within the cochlear lumen. Retro graded apical array insertion has less chances of facial nerve stimulation as it is placed away from the nerve.

Cochlear ossification in patients with profound hearing loss following bacterial meningitis

CONCLUSION

Cochlear ossification following bacterial meningitis is related to causative pathogen, but not age at disease or time point of evaluation. However, progression may occur over time, especially in case of primary signs of ossification.

OBJECTIVE

To investigate the occurrence and degree of cochlear ossification on CT and MRI in patients with bilateral profound hearing loss following bacterial meningitis, in relation to causative pathogen, age at disease, and time point of evaluation. Progression of ossification in cases that underwent more than one scan was evaluated.

METHODS

In the period 1982-2008, 47 cochlear implantations were performed in 34 consecutive candidates suffering from bilateral profound hearing loss following bacterial meningitis. A retrospective review of patient files and preoperative CT and MR images was performed.

RESULTS

Cochlear ossification was observed in 35% of patients and 26% of ears on CT. The corresponding values for MRI were 44 and 30% (difference not significant). Streptococcus pneumoniae infection caused ossification more frequently than Neisseria meningitidis. No difference was found between pediatric and adult cases, and the occurrence of ossification was not related to the time point of evaluation. Signs of progressive ossification were found in cases with two CT scans, especially if ossification was present at the first scan.

Hearing loss in adults surviving pneumococcal meningitis is associated with otitis and pneumococcal serotype

We assessed the incidence of hearing loss and its relationship with clinical characteristics and pneumococcal serotypes in adults surviving pneumococcal meningitis. We analysed hearing loss in 531 adults surviving pneumococcal meningitis included in two prospective nationwide cohort studies performed from April 1998 through to October 2002 and March 2006 through to January 2009. Hearing loss was evaluated on admission and discharge for all patients. Severe hearing loss was assessed by pure tone average on audiology and corrected for age, or by the combination of hearing loss on discharge and a score on the Glasgow Outcome Scale below 5, which could not be explained by other neurological sequelae. A total of 531 episodes of pneumococcal meningitis with non-lethal outcome were included. Predisposing conditions for pneumococcal meningitis were present in the majority of patients (64%), most commonly otitis (36%). Hearing loss was present at discharge in 116 patients (22%) and was classified as mild in 53% and severe in 47%. Hearing loss was related to otitis (odds ratio [OR], 2.58; 95% confidence interval [CI], 1.66-4.02; p < 0.001) and inversely related to serotype 23 F infection (OR, 0.36; 95% CI, 0.13-0.98; p = 0.025), but not with parameters of disease severity or indicators of cerebrospinal fluid inflammation severity. Meningitis due to pneumococcal serotype 3 was associated with the highest rate of hearing loss. Hearing loss frequently complicates pneumococcal meningitis. Risk factors for hearing loss were infection with pneumococcal serotype 23 F and otitis, but not disease severity. Otitis and resulting perilympathic inflammation contribute to meningitis-associated hearing loss.

Animal model of radiogenic bone damage to study mandibular osteoradionecrosis

OBJECTIVE

The objective of the study was to create an animal model to study mandibular osteoradionecrosis (ORN) using high-dose rate (HDR) brachytherapy.

METHODS

Ten Sprague-Dawley male rats were used in this study. Six rats received a single dose of 30 Gy using an HDR remote afterloading machine via a brachytherapy catheter placed along the left hemimandible. The remaining 4 rats served as controls with catheter placement without radiation (sham). On the day following irradiation or sham, all 3 left mandibular molars were atraumatically extracted. Twenty-eight days after irradiation, mandibles were examined using nondecalcified histology with sequential fluorochrome labeling, decalcified histology, and micro-computed tomography scanning.

RESULTS

Irradiated rats demonstrated exposed bone at the extraction sockets, whereas the control animals had complete mucosalization. Alopecia was also seen in the irradiated group. Both histologic and radiologic analyses of the mandible specimens demonstrated a reduction in bone formation in the radiated mandibles as compared with controls.

CONCLUSIONS

Our HDR brachytherapy model incorporating postradiation dental extractions has successfully demonstrated reproducible radiogenic mandibular bone damage analogous to the clinical ORN. Although clinical criteria continue to be used today in describing ORN, this model can serve as a platform for future studies to define ORN and delineate its pathogenesis.

Ectopic mineralization in the middle ear and chronic otitis media with effusion caused by RPL38 deficiency in the Tail-short (Ts) mouse

Inflammation of the middle ear cavity (otitis media) and the abnormal deposition of bone at the otic capsule are common causes of conductive hearing impairment in children and adults. Although a host of environmental factors can contribute to these conditions, a genetic predisposition has an important role as well. Here, we analyze the Tail-short (Ts) mouse, which harbors a spontaneous semi-dominant mutation that causes skeletal defects and hearing loss. By genetic means, we show that the Ts phenotypes arise from an 18-kb deletion/insertion of the Rpl38 gene, encoding a ribosomal protein of the large subunit. We show that Ts mutants exhibit significantly elevated auditory-brain stem response thresholds and reduced distortion-product otoacoustic emissions, in the presence of normal endocochlear potentials and typical inner ear histology suggestive of a conductive hearing impairment. We locate the cause of the hearing impairment to the middle ear, demonstrating over-ossification at the round window ridge, ectopic deposition of cholesterol crystals in the middle ear cavity, enlarged Eustachian tube, and chronic otitis media with effusion all beginning at around 3 weeks after birth. Using specific antisera, we demonstrate that Rpl38 is an ∼8-kDa protein that is predominantly expressed in mature erythrocytes. Finally, using an Rpl38 cDNA transgene, we rescue the Ts phenotypes. Together, these data present a previously uncharacterized combination of interrelated middle ear pathologies and suggest Rpl38 deficiency as a model to dissect the causative relationships between neo-ossification, cholesterol crystal deposition, and Eustachian tubes in the etiology of otitis media.

Magnetic resonance imaging in patients with meningitis induced hearing loss

The aim of this multicentre study was to compare T1 with T2 weighted MRI scans of the labyrinth after meningitis and to investigate whether waiting with scanning improved the reliability of diagnosing an ongoing process such as cochlear osteogenesis. Forty-five patients were included who suffered from meningitis induced hearing loss (radiological imaging <1 year after meningitis). Twenty-one gadolinium enhanced T1 and 45 T2 weighted MRI scans were scored by two radiologists regarding the condition of the labyrinth. These radiological observations were compared with the condition of the cochlea as described during cochlear implantation. A higher percentage of agreement with surgery was found for T2 (both radiologists 73%) than for T1 weighted MRI scans (radiologist 1: 62%, radiologist 2: 67%), but this difference is not significant. There was no significant difference between early (0–3 months) and late (>3 months) scanning, showing that radiological imaging soon after meningitis allows early diagnosis without suffering from a lower agreement with surgical findings.

Meningitis resulting in hearing loss and labyrinthitis ossificans - does the causative organism matter?

Our aim was to demonstrate whether one causative agent of meningitis is more likely to cause profound hearing loss and labyrinthitis ossificans. We obtained data from the New South Wales health department for cases of meningitis between 1995 and 2005 (1568 cases) and the Sydney Cochlear Implant Centre for cochlear implant patients with hearing loss secondary to meningitis from 1984 to 2005 (70 ears in 59 patients). The aetiological agents were compared with regard to their ability to cause profound hearing loss and cochlear ossification. Neisseria meningitidis resulted in 56.9% of cases of meningitis and 11.4% of the cases of profound hearing loss resulting in cochlear implantation (incidence of profound hearing loss of 0.4%). Streptococcus pneumoniae, however, caused 41.1% of meningitis but 85.7% of cochlear implantation (incidence of 4.6%). Labyrinthitis ossificans was more common after infection with Streptococcus pneumoniae but there was no statistically significant difference between Streptococcus pneumoniae, Haemophilus influenzae or Neisseria meningitidis for labyrinthitis ossificans (p = 0.45, chi-squared test). In conclusion Neisseria meningitidis meningitis carries a very low risk of profound hearing loss but Streptococcus pneumoniae meningitis a significantly higher risk.

Nitrogen and oxygen molecules in meningitis-associated labyrinthitis and hearing impairment. Infection. 2008;36:2-14. [PMID: 18084715 DOI: 10.1007/s15010-007-7153-1]

Pneumococcal meningitis remains a serious disease with a case fatality rate of 15%-25%. Furthermore, long-term residues affect up to 50% of survivors. One of the most frequent sequelae is sensorineural hearing loss, which occurs in 26% of survivors of pneumococcal meningitis. Unfortunately, sufficient treatment regimens are still missing. New insights into the pathology and pathophysiology of meningitis-associated hearing loss have come from animal models of bacterial meningitis. Most likely, bacteria reach the cochlea through the cochlear aquaeduct. Once arrived in the perilymphatic spaces, they induce a severe suppurative labyrinthitis. The blood-labyrinth barrier breaks, hair cells are damaged, and neurons in the spiral ganglion undergo cell death, leading to meningitis-associated hearing loss. Reactive oxygen and nitrogen species, in particular peroxynitrite, seem to be among the crucial mediators of cochlear damage and hearing loss during meningitis. In our rat model of pneumococcal meningitis, adjunctive therapy with the antioxidants and peroxynitrite scavengers Mn(III)tetrakis(4-bencoic acid)-porphyrin (MnTBAP) and N-Acetyl-L-Cystein (NAC) significantly attenuated acute and long-term hearing loss. In several other animal studies of pneumococcal meningitis, adjunctive antioxidant therapy also protected infected animals from intracranial complications. Therefore, the use of antioxidants seems to be a promising future treatment option in pneumococcal meningitis.

Auditory brainstem implantation to rehabilitate profound hearing loss with totally ossified cochleae induced by pneumococcal meningitis

Hearing rehabilitation by cochlear implantation is not always possible in case of total ossification after pneumococcal meningitis. We report 3 cases of postmeningitis profound hearing loss with total cochlear ossification in adults who underwent auditory brainstem implantation (Nucleus 22, Cochlear Inc., Lane Cove, Australia) between 1999 and 2004. The postoperative follow-up period ranged from 1 to 6 years. Eleven to 15 out of 22 electrodes were activated. All patients had significant speech discrimination in the sound-only mode and an enhanced lip-reading performance with the implant. Auditory brainstem implants are an efficient means of auditory rehabilitation and may be considered in selected cases of bilateral profound hearing loss with the impossibility of cochlear implantation.

Morphological correlates of acute and permanent hearing loss during experimental pneumococcal meningitis

In patients with acute bacterial meningitis, hearing loss can be transient but is often permanent. The mechanisms underlying meningitis-associated hearing loss are not fully understood. Therefore, we investigated the morphological correlates of hearing loss in a rat model of pneumococcal meningitis. Transcutaneous intracisternal injection of Streptococcus pneumoniae resulted in a dose-dependent hearing loss (determined by auditory brainstem response audiometry), which was partially reversible during the acute stage. Nevertheless, a severe permanent hearing loss persisted until 2 weeks after infection. Suppurative labyrinthitis was accompanied by blood-labyrinth barrier disruption (determined by cochlear Evans blue extravasation), which correlated closely with hearing loss during the acute stage but not after recovery. Two weeks after infection, spiral ganglion neuronal density was markedly decreased and correlated with the severity of permanent hearing loss. Neuronal loss can be explained by the new finding of meningitis-associated spiral ganglion neuronal necrosis rather than apoptosis (determined by morphology, TUNEL staining, and immunohistochemistry).

Fine structure histopathology of labyrinthitis ossificans in the gerbil model

Labyrinthitis ossificans (LO) is the pathological deposition of new bone within the lumen of the cochlea and labyrinth. This process occurs most commonly as a result of infection or inflammation affecting the otic capsule. Trauma and vascular compromise can also lead to neo-ossification within the otic capsule. The mechanism that regulates this process remains unestablished. This study details the end-stage histopathology in high-resolution plastic thin sections. Twenty Mongolian gerbils were infected by intrathecal injection of Streptococcus pneumoniae type 3 followed by subcutaneous penicillin G procaine (8 days) and were painlessly sacrificed 3 months later. The cochleas were serially divided and sectioned for light and electron microscopy. Sixteen of 20 animals (27 of 40 cochleas) demonstrated LO. Cochlear damage was most extensive in the vestibule and basal turn and decreased toward the apex, which often appeared normal. The histopathologic findings consisted of 1) new bone, calcospherites, osteoid, and fibrosis without dense connective tissue or osteoblasts extending from the endosteal wall into the lumen of the vestibule and scala tympani; 2) areas of dense connective tissue and osteoid enclosed by epithelial cells conjoined with the organ of Corti, stria vascularis, spiral ligament, and vestibular (Reissner's) membrane; and 3) partial to complete loss of the organ of Corti, spiral ligament cell bodies, stria vascularis, and spiral ganglion cells. Osteoblastic activity was not demonstrated in end-stage ossification in LO in the gerbil model. Neo-ossification appears to occur by calcospherite deposition along collagen-like fibrils within osteoid. The destruction of the organ of Corti, spiral ganglion cells, stria vascularis, and cells of Reissner's membrane and the spiral ligament occurs even in the absence of ossification of the cochlear duct.

Sensorineural hearing loss in children

During the past three to four decades, the incidence of acquired sensorineural hearing loss (SNHL) in children living in more developed countries has fallen, as a result of improved neonatal care and the widespread implementation of immunisation programmes. The overall decrease has been accompanied by a relative increase in the proportion of inherited forms of SNHL. The contribution made by one gene in particular, GJB2, to the genetic load of SNHL has strongly affected the assessment and care of children with hearing loss. These changes in the incidence of SNHL have not been seen in children living in less developed countries, where the prevalence of consanguinity is high in many areas, and both genetic and acquired forms of SNHL are more common, particularly among children who live in poverty. Focused genetic counselling and health education might lead to a decrease in the prevalence of inherited SNHL in these countries. Establishment of vaccination programmes for several vaccine-preventable infectious diseases would reduce rates of acquired SNHL. Although the primary purpose of such programmes is the prevention of serious and in many cases fatal infections, a secondary benefit would be a reduction in disease-related complications such as SNHL that cause permanent disability in survivors.

Location and Timing of Initial Osteoid Deposition in Postmeningitic Labyrinthitis Ossificans Determined by Multiple Fluorescent Labels

OBJECTIVES/HYPOTHESIS

Variable amounts of fibrosis and neo-ossification fill the cochlea following bacterial meningitis. The purpose of the study was to delineate the timing and location of initial ossification following pneumococcal meningitis, as well as subsequent remodeling and resorption, over the 3-month period after infection.

STUDY DESIGN

Randomized, double-blind study.

METHODS

Fluorochromes are compounds that specifically incorporate into ossifying bone. Sequential addition of different colored fluorochromes during osteoneogenesis define the timing and location of osteoid deposition and mineralization. Mongolian gerbils were infected by intrathecal injection of Streptococcus pneumoniae type 3, and control gerbils received saline. Both groups were injected with calcein on postoperative day 3, followed by xylenol orange, oxytetracycline, and alizarin red on days 7, 14, and 28 respectively. Ten experimental gerbils were killed 24 hours after each label, and an additional group at 84 days after infection. Two groups of 10 control gerbils were killed at 29 and 84 days after treatment. The temporal bones and tibias were harvested, embedded in plastic, and sliced with a diamond saw. Wafers at a thickness of 200 microm were mounted in sequence and examined.

RESULTS

Sixteen of 49 experimental animals (33%) were positive for at least one of the fluorescent labels. Fluorescent labeled osteoid was present at all sampling times. Label extended from the endosteal wall into the lumen of the scala tympani between the vestibule and the round window membrane. Discrete sites of fluorescence varied among specimens and were associated with the opening of the cochlear aqueduct, the scala tympani, organ of Corti, and the stria vascularis and spiral ligament in all turns from base to apex.

CONCLUSION

The results indicate that osteoid is deposited and begins mineralization by day 3 after infection, at least, and continues, at least, through the first 28 days after infection. There was no apparent resorption of new bone and remodeling by 84 days after infection.

Meningitis-associated hearing loss: Protection by adjunctive antioxidant therapy

Hearing loss is the most frequent long-term complication of pneumococcal meningitis, affecting up to 40% of survivors. Unfortunately, adjuvant therapy with dexamethasone has failed to satisfactorily reduce its incidence. Therefore, we evaluated the use of antioxidants for the adjunctive therapy of meningitis-associated deafness. Eighteen hours after intracisternal injection of 7.5 x 10(5) colony-forming units of Streptococcus pneumoniae, rats were treated systemically either with ceftriaxone and the antioxidants and peroxynitrite scavengers Mn(III)tetrakis(4-benzoic acid)-porphyrin (MnTBAP) or N-acetyl-L-cysteine (NAC) or placebo (1 ml phosphate-buffered saline) for 4 days. Hearing was assessed by auditory brainstem response audiometry. Adjunctive antioxidant therapy significantly reduced the long-term hearing loss (14 days after infection) for square wave impulses (mean hearing loss +/- SD: ceftriaxone and placebo, 45+/-26 dB; ceftriaxone and MnTBAP, 9+/-23 dB; ceftriaxone and NAC, 19+/-30 dB) as well as 1 kHz (ceftriaxone and placebo, 28+/-19 dB; ceftriaxone and MnTBAP, 10+/-16 dB; ceftriaxone and NAC, 10+/-17 dB), and 10 kHz tone bursts (ceftriaxone and placebo, 62+/-27 dB; ceftriaxone and MnTBAP, 16+/-13 dB; ceftriaxone and NAC, 25+/-26 dB). Furthermore, both antioxidants attenuated the morphological correlates of meningogenic hearing loss, namely, long-term blood-labyrinth barrier disruption, spiral ganglion neuronal loss, and fibrous obliteration of the perilymphatic spaces. Adjuvant antioxidant therapy is highly otoprotective in meningitis and therefore is a promising future treatment option.

Cochlear implants in young children

The past 20 years have seen the cochlear implant evolve from an innovative but radical concept to the standard of care in the management of children with severe to profound hearing loss. All children receiving the cochlear implant achieve substantial benefit; however, performance gains are optimized by a team approach to the evaluation and management of these children. The critical elements of this team include audiologists, speech pathologists, and surgeons with specific interest, expertise, and dedication to the management of children with cochlear implants. Children are not well served by practitioners who delegate follow-up to educational programs not experienced in children with implants. Long-term involvement and dedication on the part of teachers, speech pathologists, audiologists, surgeons, and family are critical to maximizing the benefit the child receives.

Expression of IL-5 alters bone metabolism and induces ossification of the spleen in transgenic mice

We have developed a transgenic mouse line, NJ.1638, which expresses high levels of IL-5 from T cells, with profound hematological consequences. Eosinophils comprise more than 60% of circulating white blood cells in these animals, with the total peripheral white blood cell counts increasing more than 40-fold relative to wild-type littermates. This extraordinary proliferative capacity is sustained by expanded sites of extramedullary hematopoiesis and is accompanied by multifocal, ectopic bone formation in the spleen. Histology of the splenic nodules revealed the presence of osteoid matrices and osteocytes trapped within mineralized trabecular plates. In addition, polarized light microscopy of calcified tissue sections revealed both woven bone and areas of organized lamellar bone. Morphometric assessments demonstrated that both the growth and mineralization of splenic bone occurred at rates nearly an order of magnitude higher than in skeletal bone. Skeletal bone metabolic parameters were also perturbed. We also observed heterotopic ossification of the spleen and perturbation of skeletal bone homeostasis following adoptive engraftment of transgenic marrow to wild-type recipients. These data suggest that IL-5 overexpression mediates bone formation through the mobilization of marrow-derived osteogenic progenitors and/or the inhibition of recruited osteoclasts.