Systemic steroid reduces long-term hearing loss in experimental pneumococcal meningitis

Dexamethasone protects the hearing of Meniere's disease patients after triple semicircular canal plugging

Background: TSCP has shown its efficacy in vertigo control for intractable Meniere's disease. However, hearing impairment remains a problem and hampered the application of the surgery.Aims/objectives: To investigate the effect of dexamethasone on the hearing of Meniere's disease patients after TSCP to determine whether inflammation is involved in this processMaterial and methods: Meniere's disease patients who received TSCP surgeries were treated with or without dexamethasone postoperatively. All patients' hearing function were evaluated during a follow up of 2 years after surgery and compared between the two groups.Results: Hearing worsening and word recognition score loss were milder in the dexamethasone group than in the non-dexamethasone group. The rates of profound hearing worsening and word recognition score loss remained significantly lower in the dexamethasone group than in the non-dexamethasone group even 2 years after surgery.Conclusions: Dexamethasone protects the hearing of Meniere's patients after TSCP. Inflammation may be involved in the mechanism by which TSCP causes hearing impairment in these patients.Significance: This finding suggests that steroids should be used routinely after TSCP for hearing preservation, and operative precedures need to be modified to minimize inflammation in the inner ear.

Adjuvant agents enhance round window membrane permeability to dexamethasone and modulate basal to apical cochlear gradients

Glucocorticoids have direct anti-inflammatory, anti-oxidant and anti-apoptotic effects on cochlear hair cells. Cochlear glucocorticoid therapy has gained particular attention for its ability to enhance the protection of residual hearing following hearing preservation cochlear implantation. Local drug delivery methods achieve high drug concentrations within the inner ear fluids but are reliant upon diffusion across the round window membrane. Diffusion has been shown to demonstrate large individual variability. This study explores the role of "adjuvant agents", which when administered with glucocorticoids, enhance inner ear absorption and distribution. Guinea pig cochleae were administered either dexamethasone alone or in combination with hyaluronic acid, histamine, or combination histamine and hyaluronic acid, targeted at the round window membrane. Control subjects received saline. Perilymph was sampled from the cochlear apex, and basal to apical dexamethasone concentrations recorded with mass spectroscopy. Cochleae were harvested, and immunohistochemistry employed to explore dexamethasone tissue penetration and distribution. Basal to apical gradients were observed along the scala tympani, with higher dexamethasone concentrations observed at the cochlear base. Gradients were more pronounced and uniform when administered on a hyaluronic acid sponge, while histamine increased absolute concentrations reaching the inner ear. Tissue penetration correlated with perilymph concentration. Our results demonstrate that adjuvant agents can be employed to enhance dexamethasone absorption and distribution in the inner ear, thus proposing therapeutic strategies that may enhance steroid facilitated hearing protection.

Bacterial meningitis: insights into pathogenesis and evaluation of new treatment options: a perspective from experimental studies

Bacterial meningitis is associated with high mortality and morbidity rates. Bacterial components induce an overshooting inflammatory reaction, eventually leading to brain damage. Pathological correlates of neurofunctional deficits include cortical necrosis, damage of the inner ear and hippocampal apoptosis. The hippocampal dentate gyrus is important for memory acquisition and harbors a neuronal stem cell niche, thus being potentially well equipped for regeneration. Adjuvant therapies aimed at decreasing the inflammatory reaction, for example, dexamethasone, and those protecting the brain from injury have been evaluated in animal models of the disease. They include nonbacteriolytic antibiotics (e.g., daptomycin), metalloproteinase inhibitors and modulators of the immunological response, for example, granulocyte colony-stimulating factor. Increasing research interest has recently been focused on interventions aimed at supporting regenerative processes.

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.

The role of dexamethasone in the treatment of bacterial meningitis - a systematic review

Corticosteroids are used as an adjunct to antibiotics in the treatment of bacterial meningitis in an attempt to attenuate the intrathecal inflammatory response and thereby reduce mortality and morbidity. The purpose of the present paper is to provide a review of clinical studies of corticosteroids in the treatment of bacterial meningitis. Relevant literature was found in PubMed, the Cochrane databases, and references in studies. Forty-four publications of relevance were identified, comprising 29 publications of randomised studies, 10 publications reporting either non- or quasi-randomised studies, and five reporting retrospective studies, and nine meta-analyses. Taken together, dexamethasone treatment may be associated with a lower mortality in adults and fewer neurological and auditory sequelae in adults and children from high-income countries, in particular in adults suffering from pneumococcal meningitis. In contrast, studies conducted in developing countries have yielded less favourable results.

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.