[Biological resonance as a possible mechanism of an ototoxic action of aminoglycoside antibiotics]

Literature data on mechanisms of an ototoxic action of aminoglycoside antibiotics (AGA) doubt pharmacological basis of this phenomenon. It is suggested that the above ototoxicity may result from wave interference between wave processes in the inner ear and electromagnetic AGA field. The interaction is primary, informative and initiate apoptosis of the hair cells of the internal ear. The model experiment showed feasibility of frequency-resonance interaction between AGA and biopreparations of the acoustic apparatus of the animals.

Middle ear epithelial mucin production in response to interleukin-6 exposure in vitro

OBJECTIVES

To investigate the role of the inflammatory cytokine interleukin-6 (IL-6) in the regulation of mucin secretion by middle ear epithelia.

MATERIALS AND METHODS

Primary chinchilla middle ear epithelial cultures were established and exposed to IL-6 in a dose- and time-dependent manner. Mucin secretion was characterized by exclusion chromatography and liquid scintillation.

RESULTS

Epithelial cultures exposed to increasing doses of IL-6 demonstrated greater amounts of mucin secretion (p=0.018). Additionally, cultures exposed to IL-6 at 50 ng/ml showed significant increased secretion of mucin over control in time-dependent experiments at 6-, 15- and 24-h time points (p=0.003).

CONCLUSIONS

IL-6 upregulates mucin secretion from cultured middle ear epithelial cells in a dose- and time-dependent manner. Elucidating the effect of specific cytokines on the regulation of mucin secretion is vital to understanding the pathophysiology of otitis media and the development of novel therapeutic strategies.

Transtympanic perfusion: indications and limitations

PURPOSE OF REVIEW

To review the most recent literature regarding the application of transtympanic inner ear perfusion in the treatment of inner ear disorders including Meniere disease, sudden sensorineural hearing loss, and autoimmune inner ear disease.

RECENT FINDINGS

The use of gentamicin perfusion in the management of Meniere disease with intractable vertigo has been demonstrated to have a very high rate of success, and is much less invasive than alternative surgical procedures such as vestibular nerve section or labyrinthectomy. The technique for achieving the highest rate of success while still minimizing the risk of cochleotoxicity continues to be investigated. Sustained delivery techniques such as the Silverstein MicroWick appear to achieve the best pharmacokinetic profile within the inner ear fluids. The end point of treatment does not necessarily require complete vestibular ablation to cure the patient, and shorter courses of treatment may help to reduce the risk of hearing loss. Cochlear Meniere disease can be treated with dexamethasone 4 mg/cc perfusion of the inner ear, which may improve the hearing, tinnitus, and pressure in the ear. Sudden sensorineural hearing loss has been managed with transtympanic steroid delivery, and this appears to be beneficial for some patients who have failed to respond to oral steroids, or have medical contraindications to systemic steroids.

SUMMARY

Inner ear perfusion via transtympanic delivery is an emerging technique in the management of inner ear disease. Improved results are expected over time as research in this area answers questions about dosage and delivery techniques, as well as identifying new applications and pharmaceuticals.

Sensory hair cell death and regeneration: two halves of the same equation

PURPOSE OF REVIEW

Sensory hair cells are susceptible to ototoxic damage from a variety of sources, including antibiotic treatment. Unfortunately, this often results in permanent hearing and/or balance problems in humans. By understanding how sensory hair cells die in response to aminoglycoside treatment, preventive strategies may be developed. This review will discuss some of the key recent findings in sensory hair cell death and regeneration.

RECENT FINDINGS

Aminoglycosides induce hair cell death through the initiation of apoptosis. Early and late stages of hair cell apoptosis have been defined, and several of the key molecules involved in the cascade have been identified. Moreover, specific inhibitors of apoptosis rescue hair cells from death and preserve function. Hair cell death has been shown to induce regeneration through supporting cell transdifferentiation, proliferation, and new hair cell differentiation in birds and lower vertebrates. Regeneration in the mammalian cochlea does not occur spontaneously, but genetic manipulation of cell cycle genes, induction of new hair cells through gene therapy, and introduction of stem cells into damaged cochleas suggest that repair and replacement of lost hair cells in the organ of Corti may be possible. Finally, continuing investigations of the mouse, zebrafish, and human genomes may one day enable manipulation of the cochlea so that functional regeneration is readily available as a therapeutic intervention.

SUMMARY

The discovery that hair cells can regenerate in birds and other nonmammalian vertebrates has fueled a wide range of studies to find ways to restore hearing and balance in mammals. The demonstration that apoptosis and proliferation are coupled as controlling factors in regeneration and the advent of new approaches such as gene therapy, stem cell transplantation, and genomics may lead to methods for inducing hair cell regeneration and repair in the mammalian cochlear and vestibular systems.

[Intratympanic dexamethasone injections for intractable Meniere's disease]

OBJECTIVE

To investigate the efficacy of intratympanic dexamethasone injections (IDI) for 15 patients with intractable Meniere's disease (MD).

METHOD

Dexamethasone (2.5 mg/0.5 ml) was injected into the middle ear and followed by a second injection 15 minutes later. The injection was repeated the next day and weekly for 3 weeks. Total dose of dexamethasone was 17.5 mg.

RESULT

The 15 patients were followed up for 18 months (average). Complete relief of vertigo was maintained in 10 cases, improved in 2 case, injection wos repeated 3 patients with recurrent vertigo resulted in control of vertigo. Tinnitus disappeared in 5 cases, reduced in 5 cases, unchanged in 5 cases. Hearing was improved in 10 cases, unchanged in 5 cases.

CONCLUSION

IDI is effective for intractable MD. The benefits of IDI are avoidance of systemic use of steroids, lower cost, easy application. IDI can be used as an initial surgical treatment for persistent vertigo in MD and indicated for bilateral MD.

Middle Ear Pressure Changes after Nitrous Oxide Anesthesia and Its Effect on Postoperative Nausea and Vomiting

OBJECTIVES/HYPOTHESIS

This study was designed to explore the relationship between changes in middle ear pressure associated with inhalational anesthesia and the incidence of postoperative nausea and vomiting (PONV).

STUDY DESIGN

Prospective, randomized.

METHODS

Middle ear compartment pressures were measured by tympanometry in 27 randomly assigned knee arthroscopy patients throughout the surgical procedure as well as into recovery.

RESULTS

A positive correlation between the maximum positive pressure (MPP) and maximum negative pressure (MNP) gradient and PONV was demonstrated (P <.05). The incidence of PONV in the nitrous oxide (N2O) treatment group was 6 of 16 patients, whereas only 2 of 11 patients in the control group developed nausea, vomiting, and vertigo symptoms. Those patients that did not experience PONV demonstrated a median MPP of 155 with a median MNP of -52. The patients that experienced PONV exhibited a median MPP of 179 with a median MNP of -164. This demonstrates a significant increase in the incidence of PONV in the N2O treatment group.

CONCLUSIONS

Barometric changes in the middle ear contribute to the incidence of PONV induced by N2O.

Animal ototoxicity of topical antibiotics and the relevance to clinical treatment of human subjects

OBJECTIVE

The objective of this study was to systematically review the literature on animal ototoxicity from ototopical medications. A secondary objective was to assess the relevance of animal data to the use of ototopical drops in clinical situations involving humans.

STUDY DESIGN

We performed a MEDLINE search of the published literature using appropriate search terms to identify pertinent articles, which were reviewed, summarized, and tabulated.

RESULTS

One hundred seventy-three articles were reviewed; 61 articles were appropriate to the study question and were further analyzed.

CONCLUSIONS

Virtually all studies demonstrate that aminoglycoside antibiotics, when applied topically into the middle ear space, are ototoxic in experimental animals.

M??ni??re??s disease

PURPOSE OF REVIEW

Ménière's disease is characterized by spontaneous attacks of vertigo, fluctuating sensorineural hearing loss, aural fullness, and tinnitus. The pathologic process involves distortion of the membranous labyrinth with the formation of endolymphatic hydrops. This review describes the pathogenesis and etiology as well as the diagnosis and treatment of Ménière's disease.

RECENT FINDINGS

Initial management of Ménière's disease can involve a low-salt diet and a diuretic. Treatment with intratympanic injection of gentamicin can be beneficial when vertigo persists despite optimal medical management. Recent studies have shown that gentamicin reduces vestibular function in the treated ear, although complete ablation of this vestibular function is not typically required in order to achieve control of vertigo.

SUMMARY

Vertigo is often the most debilitating symptom associated with Ménière's disease. Many treatment options exist for the management of vertigo. Intratympanic injection of gentamicin (low dose) can be used in patients for whom vertigo has not been controlled by medical measures. Ongoing research is providing a greater understanding of the effects of gentamicin on vestibular function and of the mechanisms through which gentamicin leads to control of vertigo.

Tolerability of N-chlorotaurine in the guinea pig middle ear: a pilot study using an improved application system

The tissue tolerance of N-chlorotaurine (NCT), a mild endogenous antimicrobial oxidant, has been investigated by application to the guinea pig middle ear. The animals were implanted with a novel cannula system that allows chronic external drug delivery to the round window niche. In the first part of the study, 3 animals each received 100 microL of 0.1% NCT (5.5 mmol/L) and 1% NCT, respectively, in aqueous solution twice daily for 8 days. In the second part, NCT was dissolved in phosphate-buffered saline solution to 300 milliosmolar (isotonic), and 27 microL was injected in 3 additional animals twice daily for 7 days. The guinea pigs injected with 100 microL of NCT developed immediate dizziness and nystagmus and did not thrive. Other reactions included mucosal thickening in the middle ear, rupture of the tympanic membrane, and blood and gelatinous material in the cochlea accompanied by hair cell loss and a 10- to 90-dB elevation of the hearing threshold as determined by auditory brain stem responses. The effects seemed to be dose-dependent, but the rate of variability was high across animals. In contrast, the guinea pigs treated with 27 microL of isotonic NCT showed no signs of discomfort, no or only moderate thickening of the middle ear mucosa, no shift of the hearing threshold, and no hair cell loss. Positive control animals injected with 10% neomycin sulfate developed extensive hair cell loss. Provided that the membranes of the inner ear are intact and that low single-dose volumes are used to avoid increased middle ear pressure, isotonic NCT seems to be well tolerated in the tympanic cavity. The new drug delivery system proved to be advantageous for ototoxicity studies.

Intratympanale Intervalltherapie des Morbus Meni�re mit Gentamicin unter Erhalt der Kochleafunktion

For the effective treatment of Menière's disease, gentamicin should be administered at most three times: on days 1, 8 and 15. More than 50% ( n=30) of 57 patients seen between 1997 and 2000 only needed a single dose of gentamicin to obtain a sufficient reaction (single shot-therapy). Vertigo attacks were controlled in 95% of our 57 patients and there were no substantial hearing losses. Four patients lost 15 dB. Tinnitus (46%) and ear pressure (69%) could be controlled or improved. The intratympanic injection-technique (single dose=0.3 ml=12 mg) performed under local anaesthesia is simple and superior to any other procedure. The peak concentration of gentamicin is reached after 2-6 days (average 4.6 days). As soon as signs of inner ear reaction are observed, treatment has been effective and must be stopped immediately to avoid over-intoxication and damage to the cochlea.

The effect of changes in ambient oxygen concentration on the bioelectric properties of middle ear mucosa

The purpose of the present study was to compare the effect of 24 h of exposure to 7% O2 (normal middle ear physiological conditions) vs. 21% O2 (found in the middle ear after ventilation tube placement) on transepithelial Na+ absorption and Cl- secretion in cultured gerbil middle ear epithelial cell monolayers. Although no difference in apical Na+ absorption was identified, the UTP-induced stimulation of apical Cl- secretion in the presence of apical Na+ channel blockade with amiloride was significantly enhanced after exposure to 21% O2 compared with 7% O2 exposure. In the presence of a calcium-activated Cl- channel inhibitor, DIDS, UTP-induced stimulation of Cl- secretion after 21% O2 exposure was decreased, suggesting a role for calcium-activated Cl- channels in middle ear Cl- secretion in response to relative hyperoxia.

Penetration of cefprozil to middle ear effusion in children with chronic otitis media with effusion

BACKGROUND

Because of chronic otitis media with effusion (COME) demonstrates pathogenic bacteria, treatment with appropriate antibiotic is reasonable.

OBJECTIVE

We determined the penetration of cefprozil into the middle ear effusion (MEE) in children with COME.

MATERIALS AND METHODS

25 patients 2-13 years of age with COME were eligible for study. After the single dose of 15 mg/kg patients were assigned to have MEE, and serum samples were obtained during ventilation tube insertion at 0.5, 2, 3, 5, or 6 h after administration of the dose. The concentration of cefprozil was measured using validated high performance liquid chromatography method.

RESULTS

The mean concentrations of cefprozil in the MEE ranged from 0.4 to 4.4 microg/ml. The penetration into MEE was rapid and effective. Cefprozil in the MEE was maintained at a greater level than MIC 90 in S. pneumoniae for at least 6 h after administration of 15 mg/kg.

CONCLUSION

Cefprozil penetrated well into the MEE in children with COME.

Effect of positional change and inhalant anesthesia on parameters of acoustic reflectometry

OBJECTIVE

Purpose of this study was to find out the effect of positional change and inhalant anesthesia on acoustic reflectometry (AR) parameters (reflectivity and curve angle).

METHOD

AR parameters were measured on 58 ears with otitis media in sitting position before anesthesia and in supine position under inhalant anesthesia, subsequently.

RESULTS

Under anesthesia, ears with effusion disclosed more changes in reflectivity (Chi-squared analysis, chi2-test; P<0.05) and curve angle (P>0.1) than those without effusion. Further, inhalant anesthesia caused more changes in the false negative ears (63.63%) than in those with effusion having positive test before anesthesia (12.90%) (P<0.001).

CONCLUSIONS

From the data of this study, it could be said that reflectivity shows changes according to the amount of effusion which is in contact with the tympanic membrane under anesthesia, and that curve angle becomes more sensitive to detect effusion when anesthetic gas diffuses into the middle ear with effusion, probably due to the pushing of effusion towards the tympanic membrane.

Hearing Loss after Intratympanic Gentamicin Therapy for Unilateral Ménière's Disease

OBJECTIVE

This study set out to evaluate the hearing changes that occur during intratympanic gentamicin therapy and to correlate them with the long-term effects of the treatment on the control of vertigo and on hearing.

STUDY DESIGN

This was a prospective study.

SETTING

Tertiary medical center.

PATIENTS

The 71 patients included in the study had been diagnosed with unilateral Ménière's Disease as defined within the 1995 American Academy of Otolaryngology-Head and Neck Surgery guidelines, and had been refractory to medical treatment for at least 1 year.

INTERVENTION

Intratympanic injections of gentamicin at a concentration of 27 mg/ml were performed at weekly intervals until indications of vestibular hypofunction appeared in the treated ear. If there was a recurrence of the episodes of vertigo, an additional course of injections was performed.

MAIN OUTCOME MEASURE

The 1995 American Academy of Otolaryngology-Head and Neck Surgery criteria for reporting the treatment outcome for Ménière's Disease were used. During the period of gentamicin instillation, weekly audiograms were obtained. The results of the treatment were expressed in terms of control of vertigo and hearing level.

RESULTS

Vertigo was controlled by gentamicin instillation in 83.1% of the 71 patients. Two years after the treatment, hearing loss as a result of the gentamicin injections was observed in only 11 (15.5%) patients. The recurrence of spells of vertigo after having initially achieved complete control was noted in 17 (23.9%) patients. Hearing loss at the end of the treatment occurred in 32.4% of the patients, but it was transitory so that 3 months after ending the treatment it was 12.7% and after 2 years it was 15.5%. Those patients in whom no change in their level of hearing occurred during the treatment needed another course of injections and presented poorer overall control of vertigo.

CONCLUSIONS

Ending weekly intratympanic injections when clinical signs of vestibular deafferentation appear results in the control of vertigo in the majority of patients. The hearing changes detected during the treatment are transitory and are the only clinical sign that predicts the response to gentamicin instillation.

Therapeutic effects of eustachian tube surfactant in barotitis media in guinea pigs

BACKGROUND

Previous research has shown that the eustachian tube (ET) in animals and humans is lined with a substance that lowers surface tension and thus facilitates the opening of the eustachian tube and aeration of the middle ear. The aims of the present study were to observe the role of eustachian tube surfactant (ETS) on the opening of the ET and to explore the therapeutic effect of natural and artificial ETS on barotitis media (BOM).

METHODS

BOM was successfully established in 50 guinea pigs by simulated ascent in an altitude chamber. Subsets of the affected ears were treated by flushing with natural ETS, artificial ETS, artificial phospholipid, or saline. The effects were evaluated by measuring eustachian tube pressure opening level (POL). Other animals with BOM were treated with artificial ETS on one side and saline in the other, after which the clinical signs were observed.

RESULTS

The POL of the saline group remained unchanged. Natural ETS decreased the POL from 11.98 to 6.11 kPa (p < 0.01); artificial ETS reduced the POL from 11.91 to 6.67 kPa (p < 0.01); there was no significant difference between the two treatments. Artificial phospholipid was less effective, decreasing POL from 11.86 to 8.61 kPa (p < 0.05). Clinical observations showed that after 1 wk of treatment with artificial ETS, the congestion in the tympanic membrane was alleviated, the hearing threshold improved, and the effusion in tympanic cavity diminished.

CONCLUSION

Artificial ETS was as effective as natural ETS in facilitating the opening of eustachian tube and had definite therapeutic effects on BOM in this model.

Middle ear epithelial mucin production in response to interleukin 1β exposure in vitro

OBJECTIVES: To investigate the role of the inflammatory cytokine interleukin-1β (IL-1β) in the regulation of mucin secretion by middle ear epithelia.

STUDY DESIGN AND SETTING: Primary chinchilla middle ear epithelial cultures were established and exposed to IL-1β in a dose- and time-dependent manner. Mucin secretion was characterized by exclusion chromatography and liquid scintillation.

RESULTS: Epithelial cultures exposed to increasing doses of IL-1β demonstrated greater amounts of mucin secretion ( P = 0.007). Additionally, cultures exposed to IL-1β at 50 ng/mL showed increased secretion of mucin over control noticeable at 6 hours, but significant at the 15- and 24-hour time points ( P > .0001 for each).

CONCLUSIONS: IL-1β upregulates mucin secretion from cultured middle ear epithelial cells in a dose-and time-dependent manner.

SIGNIFICANCE: Elucidating the effect of specific cytokines on the regulation of mucin secretion is vital to understanding the pathophysiology of otitis media and the development of novel therapeutic strategies.

Retinoic acid depletion induces keratinizing squamous differentiation in human middle ear epithelial cell cultures

OBJECTIVE

The pathogenesis of cholesteatoma behind an intact tympanic membrane remains controversial. Squamous metaplasia of the middle ear mucosa is thought to be a possible mechanism in such cases. However, to date, no definitive experimental results have proved this association. This study was undertaken to investigate whether normal human middle ear epithelial (NHMEE) cells undergo keratinizing squamous differentiation in a retinoic acid (RA)-deficient culture.

MATERIAL AND METHODS

We examined the morphological differences between RA-deficient and -sufficient cultures, and determined the expressions of the mucin gene and cornifin-alpha mRNAs as indicators of mucous and squamous differentiation, respectively.

RESULTS

Histomorphologically, the NHMEE cells differentiated into a keratinizing squamous epithelium in RA-deficient cultures. In addition, the expressions of mucin gene 5AC (MUCSAC) and MUC8 mRNAs were suppressed, and the expression of cornifin-alpha mRNA increased progressively as a function of differentiation in RA-deficient cultures.

CONCLUSIONS

This study shows that RA depletion induces keratinizing squamous differentiation in NHMEE cell cultures. This finding supports the hypothesis that middle ear cholesteatoma originates from metaplastic middle ear mucosa.

Effect of uridine 5'-triphosphate on mucin and lysozyme expression in human middle ear epithelial cells

OBJECTIVE

Extracellular uridine 5'-triphosphate (UTP) regulates a variety of biological functions in the airway epithelium, including chloride and fluid transport, mucociliary clearance and mucin secretion via the P2Y purinergic receptors. This study was undertaken to investigate which P2Y purinergic receptors are expressed in normal human middle ear epithelial (NHMEE) cells. We also determined the levels of mucin and lysozyme secretion and their mRNA expressions following stimulation with UTP in passage-2 cultured NHMEE cells.

MATERIAL AND METHODS

An immunoblotting assay was performed for quantitation of mucin and lysozyme proteins and RT-PCR for their gene levels after treatment with UTP was done in normal human middle ear epithelial cells.

RESULTS

Middle ear epithelial cells expressed P2Y1, P2Y2, P2Y6, P2Y11, and P2Y12 receptors but not P2Y4 receptor. Apically applied UTP induced increased mucin and lysozyme secretion, as measured by dot blotting. In contrast, UTP did not enhance mucin and lysozyme mRNA expression until 72 h after treatment.

CONCLUSION

This study suggests that UTP acts as a secretogogue on mucin and lysozyme secretion in NHMEE cells via the P2Y2 and/or P2Y6 receptor.

Middle ear fluid histamine and leukotriene B4 in acute otitis media: effect of antihistamine or corticosteroid treatment

OBJECTIVE

Two potent mediators of acute inflammation, histamine and leukotriene B4 (LTB4), have been shown to play important roles in the pathogenesis and clinical course of acute otitis media (AOM) in children. The purpose of this study was to evaluate the ability of adjuvant drugs, antihistamine and corticosteroid, in reduction of the levels of histamine and LTB4 in the middle ear and their ability to improve outcomes of AOM.

METHODS

Eighty children with AOM (aged 3 months to 6 years) were enrolled in a prospective, randomized, double-blind, placebo controlled study. All children received one dose of intramuscular ceftriaxone and were randomly assigned to receive either chlorpheniramine maleate (0.35 mg/kg per day) and/or prednisolone (2 mg/kg per day) or placebos three times a day for 5 days. Tympanocentesis was performed at enrollment and after 5 days of adjuvant drug treatment. MEFs were collected for bacterial and viral studies and histamine and LTB4 levels. The subjects were followed for the duration of middle ear effusion or up to 3 months.

RESULTS

Histamine or LTB4 levels in the MEF after 5 days of treatment were not significantly reduced by adjuvant drug treatment. However, subjects receiving corticosteroid had a lower rate of treatment failure during the first 2 weeks and shorter duration of middle ear effusion.

CONCLUSIONS

Five day of antihistamine or corticosteroid treatment does not reduce the levels of histamine or leukotriene B4 in the MEF of children with AOM. Positive clinical outcomes of AOM cases associated with corticosteroid treatment needs to be confirmed in a larger clinical trial of children with intact tympanic membranes, who do not receive tympanocentesis.

A systematic review of the effectiveness of ofloxaxin otic solution for the treatment of suppurative otitis media

The objectives of the study were to determine the effectiveness and incidence of adverse events of ofloxacin otic solution for suppurative otitis media compared with other treatments. All randomized controlled trials and nonrandomized comparative clinical trials published from 1966 to 2000 using ofloxacin otic solution as one of the interventions were reviewed and data were extracted and analyzed. Eleven clinical trials (9 randomized and 2 nonrandomized) enrolling 1,484 adults and children were finally included in the analysis. Five studies employed clear concealment procedure in the allocation of treatment whereas evaluation of outcome was at least single-blinded in 6 trials. The probability of overall cure rate was higher with 0.3% ofloxacin otic solution than with other topical or systemic antibiotics in 9 of the studies analyzed (OR = 2.67; 95% CI = 2.04, 3.50). Resolution of secondary outcome parameters evaluated at least 1 week after treatment was higher with 0.3% ofloxacin otic solution: resolution of otalgia (4 trials; OR = 2.41; 95% CI = 1.2, 4.82); resolution of otorrhea (11 trials; OR = 2.78; 95% CI = 2.12, 3.65), and bacterial eradication rate (6 trials; OR = 3.86; 95% CI = 2.54, 5.87). A subgroup analysis of 4 studies comparing ofloxacin otic solution with antibiotic- and steroid-containing otic solution showed a higher cure rate for ofloxacin otic solution (OR = 2.73; 95% CI = 1.52, 4.90). Another subgroup analysis on 3 studies comparing ofloxacin otic solution with oral systemic antibiotics showed higher resolution of otorrhea with ofloxacin otic solution (OR = 2.78; 95% CI = 2.12, 3.65). Of 4 studies with data on adverse events, the probability of adverse events was lower with ofloxacin otic solution than with other topical antibiotics (OR = 0.28; 95% CI = 0.19, 0.42). Subgroup analysis showed that 0.3% ofloxacin otic solution showed better results in terms of overall cure rate, resolution of otorrhea, otalgia, bacterial eradication rate and incidence of adverse events. Whether due to chronic suppurative otitis media (CSOM) or draining tympanostomy tube, the overall cure rate (CSOM OR = 4.86; with tympanostomy tube OR = 2.13) and resolution of otorrhea (CSOM OR = 4.42; with tympanostomy tube OR = 1.66) were likewise in favor of 0.3% ofloxacin otic solution. The studies included in this meta-analysis showed generally homogenous results in all clinical and laboratory outcomes analyzed, except for the evaluation of adverse events. The authors conclude that 0.3% ofloxacin otic solution is better than other otic antibiotic drops and other oral antibiotics in terms of overall cure rate and resolution of secondary outcome parameters. Estimates on the beneficial effects of ofloxacin otic solution are limited to the period of study included in this review.

Effects of trolox, locally applied on round windows, on cisplatin-induced ototoxicity in guinea pigs

OBJECTIVE

Cisplatin (CDDP), an antitumor agent widely used in the treatment of pediatric solid tumors, has dose-limiting side effects such as ototoxicity and nephrotoxicity. Recently, evidence has been accumulated to demonstrate that these side effects are closely related to oxidative stress. In the present study, we attempted to suppress CDDP-induced ototoxicity in guinea pigs by administering trolox, a water-soluble analogue of alpha-tocopherol which is a natural lipid-soluble antioxidant, locally on round windows.

METHODS

Hartley albino guinea pigs (250-300 g) were treated with CDDP (0.3 mg/ml) in the presence or absence of a combined treatment of trolox (5 mM). Both drugs were administered locally on round windows.

RESULTS

The combined treatment of trolox distinctly improved the ototoxic side effects induced by CDDP. These were: elevation of auditory brain stem response threshold at 4, 8 and 16 kHz and substantial losses of outer hair cells with the base-to-apex gradient.

CONCLUSION

Trolox, locally applied on round windows, showed a suppression on CDDP-ototoxicity. The results obtained in the present study suggest that a local application of trolox in the tympanic cavity can be a promising candidate to prevent the CDDP-ototoxicity in the future.

Gentamicin tympanoclysis: effects on the labyrinthine sensory cells

OBJECTIVES

The objective of the study was to determine whether a selective vestibular hair cell toxicity with sparing of the cochlear hair cells could be achieved by infusing different concentrations of gentamicin into the middle ears of adult cats.

STUDY DESIGN

Prospective experimental animal study treating only the left ear of each cat, the right ear serving as individual control.

METHODS

Gentamicin solution at concentrations of either 30 or 3 mg/mL was infused daily into the left middle ear of adult cats until overt ataxia occurred. After 1 month or 6 months, each cat was killed and its temporal bones prepared for optical microscopy.

RESULTS

Animals treated with 30 mg/mL gentamicin until ataxic required a median of five daily doses. These animals had clear-cut cochlear basal turn hair cell losses accompanying toxic lesions in the utricle and cristae. In contrast, animals treated with 3 mg/mL gentamicin until ataxic required an average of 19 daily doses. These animals had lesions restricted to the utricle and cristae with sparing of the cochlea hair cells. Animals that failed to develop ataxia manifested neither lesions of the cochlear nor vestibular hair cells.

CONCLUSION

Gentamicin tympanoclysis in the cat animal model, using a dilute solution and continued once daily until clinical ataxia occurs, is capable of producing selective vestibular hair cell toxicity while sparing cochlea hair cells.

The effect on the middle-ear cavity of an absorbable gelatine sponge alone and with corticosteroids

The objectives of this study were to establish whether there is an obvious difference between intact mucosa and abraded mucosa of the middle-ear cavity in respect to the potential side effects from the application of absorbable gelatine sponge (Gelfoam) and to investigate if Gelfoam combined with corticosteroid ointment (cortimycine, sterile 1% hydrocortisone acetate) can reduce the occurrence of these effects. Twenty Albino rats were used in the study. These animals were divided into four groups, with ten ears in each group. In group A, the middle-ear mucosa was kept intact, and Gelfoam was inserted into the middle-ear cavity. In group B, the middle-ear mucosa was abraded, and Gelfoam was inserted. In group C, Gelfoam with corticosteroid was implanted over the intact mucosa, and in group D, the mucosa was abraded prior to the insertion of Gelfoam with corticosteroid. The changes were evaluated 8 weeks postoperatively. In group A, there was a minimal increase in fibroblastic activity, vascular proliferation with mild to moderate fibrosis and all but two tympanic membranes were perfectly normal. However, in group B, we encountered a significant increase in fibroblastic activity, vascular proliferation and fibrosis, and we observed that all tympanic membranes were moderately to severely thickened. These histopathologic changes related to Gelfoam were noted to be decreased in group C and especially in group D. As previously reported in the literature, Gelfoam was found to promote the formation of connective tissue in the middle-ear cavity regardless of the status of the mucosa. The unwanted effects of this material may be decreased if it is combined with corticosteroids in the middle-ear cavity.

Mechanisms responsible for postnatal middle ear amniotic fluid clearance

Neonatal guinea pigs show signs of a temporary conductive hearing loss during the first few days after birth. It has been suggested that this is due mainly to the presence of amniotic fluid in the middle ear (ME) cavity at birth and its subsequent clearance. This study was designed to try to identify the mechanisms responsible for the amniotic fluid clearance from the ME after birth by means of several experiments in guinea pigs. The osmolarity of the blood, amniotic fluid and the fluid in the ME cavity of guinea pig fetuses was measured. Serum and normal saline were introduced into the ME of older animals and fluid clearance was monitored short- and long-term by microscopic observation, tympanometry and estimation of residual fluid. Following instillation of 1/5 normal saline and normal saline into the ME cavity, the osmolarity of the remaining fluid was determined, short- and long-term. Clear osmotic pressure gradients were found between amniotic fluid (low pressure), fetal blood (higher pressure) and the fluid in the fetal ME (intermediate between them). The MEs into which normal saline had been introduced developed negative pressure and, over several days, were cleared of fluid. When serum was applied, ME pressure remained close to atmospheric and the fluid was not cleared. Hypotonic saline application led to an increase in the osmotic pressure in the fluid remaining in the ME. It is concluded that most of the amniotic fluid is cleared from the neonatal ME cavity by water outflow into the blood due to osmotic pressure gradients.