Purinergic Signaling and Cochlear Injury-Targeting the Immune System?

Hearing impairment is the most common sensory deficit, affecting more than 400 million people worldwide. Sensorineural hearing losses currently lack any specific or efficient pharmacotherapy largely due to the insufficient knowledge of the pathomechanism. Purinergic signaling plays a substantial role in cochlear (patho)physiology. P2 (ionotropic P2X and the metabotropic P2Y) as well as adenosine receptors expressed on cochlear sensory and non-sensory cells are involved mostly in protective mechanisms of the cochlea. They are implicated in the sensitivity adjustment of the receptor cells by a K⁺ shunt and can attenuate the cochlear amplification by modifying cochlear micromechanics. Cochlear blood flow is also regulated by purines. Here, we propose to comprehend this field with the purine-immune interactions in the cochlea. The role of harmful immune mechanisms in sensorineural hearing losses has been emerging in the horizon of cochlear pathologies. In addition to decreasing hearing sensitivity and increasing cochlear blood supply, influencing the immune system can be the additional avenue for pharmacological targeting of purinergic signaling in the cochlea. Elucidating this complexity of purinergic effects on cochlear functions is necessary and it can result in development of new therapeutic approaches in hearing disabilities, especially in the noise-induced ones.

Innovative pharmaceutical approaches for the management of inner ear disorders

The sense of hearing is essential for permitting human beings to interact with the environment, and its dysfunctions can strongly impact on the quality of life. In this context, the cochlea plays a fundamental role in the transformation of the airborne sound waves into electrical signals, which can be processed by the brain. However, several diseases and external stimuli (e.g., noise, drugs) can damage the sensorineural structures of cochlea, inducing progressive hearing dysfunctions until deafness. In clinical practice, the current pharmacological approaches to treat cochlear diseases are based on the almost exclusive use of systemic steroids. In the last decades, the efficacy of novel therapeutic molecules has been proven, taking advantage from a better comprehension of the pathological mechanisms underlying many cochlear diseases. In addition, the feasibility of intratympanic administration of drugs also permitted to overcome the pharmacokinetic limitations of the systemic drug administration, opening new frontiers in drug delivery to cochlea. Several innovative drug delivery systems, such as in situ gelling systems or nanocarriers, were designed, and their efficacy has been proven in vitro and in vivo in cochlear models. The current review aims to describe the art of state in the cochlear drug delivery, highlighting lights and shadows and discussing the most critical aspects still pending in the field.

[The estimation of the efficacy of manual therapy included in the combined treatment of cochlear-vestibular disorders based on the results of computed stabilography]

The objective of the present study was to estimate the efficacy of the combined treatment of spondylogenic cochlear-vestibular disorders with the use of both medicamental and non-medicamental modalities. Computed static stabilometry was applied for diagnostics of postural disbalance and evaluation of the treatment outcomes. It was shown that the application of manual therapy for the management of 56 patients presenting with spondylogenic cochlear-vestibular disorders resulted in the decrease of tinnitus and the improvement of vestibular and cochlear functions.

Deterioration of hearing in a cochlear implantee with relapsing polychondritis

We report on a rare case of cochlear implantation in a patient affected by relapsing polychondritis (RP), which over time induced cochlear fibrosis/ossification and deterioration of previously excellent hearing performance. The clinical course was determined by CT scan, electrophysiology, and speech perception data. We conclude that RP is a severe autoimmune connective disorder that can cause profound sensorineural hearing loss. Cochlear implantation in these patients can provide excellent performance. Continuation of therapy may improve prognosis, but relapses involving inner ear structures can determine fibrosis/ossification of the modiolus and interfere with cochlear implant use.

[Cochleovestibular disorders: approaches to diagnostics and treatment]

The aim of this work was to evaluate the efficacy of introduction of milgamma and milgamma compositum in the treatment of 52 patients with cochleovestibular disorders of different etiology. Thirteen patients enrolled in the study received standard therapy and 39 others were given its combination with milgamma preparations. Combined therapy with milgamma and milgamma compositum ensured faster vestibular compensation including posturographic characteristics than the standard treatment (within 3-4 weeks compared with 5 weeks in controls). The results of the study give reason to recommend milgamma and milgamma compositum as neurotropic medicines in addition to standard therapy for the management of the patients presenting with cochleovestibular disorders for the acceleration of the vestibular compensation.

Ginkgo biloba extract (EGb761) protects against aging-related caspase-mediated apoptosis in rat cochlea

CONCLUSIONS

EGb761 treatment has a significant benefit with an early and preventive effect, reversing the deleterious effect of aging in the integrity of the rat cochlea, even in the late stage of the rat lifespan.

OBJECTIVES

We previously reported a significant relationship between aging and apoptosis in the rat cochlea. This study was designed to investigate the effects of Ginkgo biloba leaf extract (EGb761) on age-associated cochlear caspase activation.

METHODS

Sprague-Dawley rats (n = 80) divided into two groups according to their age (4 months old, younger, YR, and 12 months old, aged-mature, AM) were treated with 100 mg/kg/day body weight of EGb761 extract dissolved in tap water for two periods: 4 and 12 months. Then cochleae were harvested to measure caspase activities, ATP levels, total superoxide dismutase (SOD) activity, and caspase-3 gene expression. Auditory steady-state responses (ASSR) threshold shifts were also measured before sacrifice of the rats.

RESULTS

EGb761 treatment prevents significantly aging-related caspase-induced activities within the cochleae in YR and AM rats. In the short EGb761 treatment, YR rats showed lower levels of caspase-3/7 than AM rats. In contrast, longer treatment did not show significant differences between YR and AM rats. Reduced caspase-3/7 activity in presence of EGb761 correlates with significant improvements of ASSR threshold shifts.

Blockade of interleukin-6 signaling suppressed cochlear inflammatory response and improved hearing impairment in noise-damaged mice cochlea

Hearing impairment can be the cause of serious socio-economic disadvantages. Recent studies have shown inflammatory responses in the inner ear co-occur with various damaging conditions including noise-induced hearing loss. We reported pro-inflammatory cytokine interleukin-6 (IL-6) was induced in the cochlea 6h after noise exposure, but the pathophysiological implications of this are still obscure. To address this issue, we investigated the effects of IL-6 inhibition using the anti-IL-6 receptor antibody (MR16-1). Noise-exposed mice were treated with MR16-1 and evaluated. Improved hearing at 4kHz as measured by auditory brainstem response (ABR) was noted in noise-exposed mice treated with MR16-1. Histological analysis revealed the decrease in spiral ganglion neurons was ameliorated in the MR16-1-treated group, while no significant change was observed in the organ of Corti. Immunohistochemistry for Iba1 and CD45 demonstrated a remarkable reduction of activated cochlear macrophages in spiral ganglions compared to the control group when treated with MR16-1. Thus, MR16-1 had protective effects both functionally and pathologically for the noise-damaged cochlea primarily due to suppression of neuronal loss and presumably through alleviation of inflammatory responses. Anti-inflammatory cytokine therapy including IL-6 blockade would be a feasible novel therapeutic strategy for acute sensory neural hearing loss.

Ginsenoside Rb1 protects against damage to the spiral ganglion cells after cochlear ischemia

The effects of transient cochlear ischemia on spiral ganglion cells (SGCs) were studied in Mongolian gerbils. Ischemic insult was induced by occluding the bilateral vertebral arteries of gerbils for 15min. Seven days after ischemia, the percentage of SGCs decreased to 67.5% from the preischemic baseline in the basal turn. Evaluation with immunohistochemical staining showed TUNEL-positive reactions in the SGCs with fragmented nuclei. In addition, we investigated the protective effects of ginsenoside Rb1 (gRb1) against ischemic injury to SGCs. Seven days after ischemia, the auditory brainstem response threshold shift was significantly reduced and the percentage of SGCs decreased to 90.2% from the preischemic baseline in the basal turn in the gRb1-treated group. These findings suggest that gRb1 prevented hearing loss caused by ischemic injury to SGCs in Mongolian gerbils.

The effects of the glucocorticoid receptor antagonist RU486 and phospholipase A2 inhibitor quinacrine on acoustic injury of the mouse cochlea

Glucocorticoids are used clinically for the treatment of acoustic injury. However, the protective mechanism of glucocorticoid in acoustic injury has not been completely clarified. Also, the effects of phospholipase A2 (PLA2) on acoustic injury have not been examined to the best of our knowledge. The purpose of the present study was to examine the effects of methylprednisolone, a glucocorticoid receptor inhibitor (RU486) and a phospholipase A2 inhibitor (quinacrine) on cochlear injury induced by acoustic overexposure. Seventy-eight mice were exposed to a 4kHz pure tone at 128dB SPL for 4h. The auditory brainstem response (ABR) was used to examine the hearing thresholds. Cochlear morphology was examined to estimate the outer hair cell loss induced by acoustic overexposure. Methylprednisolone and quinacrine significantly alleviated the hearing threshold shift and hair cell loss induced by acoustic overexposure. RU486 antagonized the protective effect of methylprednisolone. The present findings suggest firstly that glucocorticoids exert protective effects against acoustic injury; secondly, that the protective effect of methylprednisolone was exerted by binding glucocorticoid receptors, and finally that activation of PLA2 may be involved in acoustic injury.

SUSAC SYNDROME IN FOUR MALE PATIENTS

PURPOSE

To report the clinical and imaging features in four male patients presenting with Susac syndrome, a microangiopathy affecting the brain, the retina, and the cochlea.

METHODS

Retrospective review of clinical data, fluorescein angiograms, and magnetic resonance imaging findings in these four cases.

RESULTS

All four patients were young men (range, 20-35 years). The axiomatic triad of ocular, cochlear, and neurologic involvement was present in three patients. Neurologic symptoms were absent in the fourth one. Fluorescein angiography showed arteriolar wall hyperfluorescence in all four patients. Magnetic resonance images showed in three patients multifocal hyperintense lesions in the white matter and the corpus callosum with typical involvement of the central fibers. Therapeutic modalities and clinical course are described. Three patients had a follow-up of 3, 5, and 13 years with complete remission of the disease within 1 year in all three cases. One patient had severe neuropsychological sequelae.

CONCLUSION

Susac syndrome seems to be less unusual in men than previously reported. Though presenting as a self-limited monophasic course disease in most cases, it may result in severe neuropsychological sequelae. Early diagnosis of the syndrome is enabled by the combination of the ophthalmologic, audiometric, and brain magnetic resonance features.

Triamcinolone acetonide protects auditory hair cells from 4-hydroxy-2,3-nonenal (HNE) ototoxicity in vitro

CONCLUSION

Triamcinolone acetonide crystalline suspension (e.g. Volon A) was not ototoxic to the auditory hair cells present within organ of Corti explants and protected them from an ototoxic molecule, i.e. 4-hydroxy-2,3-nonenal (HNE), that is produced within the organ of Corti as a result of oxidative stress-induced damage.

OBJECTIVES

To test the corticosteroid, triamcinolone acetonide, for ototoxicity and otoprotective capacity in organ of Corti explants.

MATERIALS AND METHODS

Organ of Corti explants excised from 4-day-old rats were the test system, HNE was the ototoxin challenge. Hair cell integrity counts were performed with fluorescent microscopy on fixed explants stained with FITC-labeled phalloidin. Statistical significance was set at p<0.05.

RESULTS

Triamcinolone acetonide did not affect hair cell integrity in the organ of Corti explants and it provided a high level of protection of hair cells against the ototoxic effects of a damaging level of HNE as determined by hair cell density counts.

Cochlear Protection by Local Insulin-Like Growth Factor-1 Application Using Biodegradable Hydrogel

OBJECTIVE

The aim of this experimental study was to examine the potential of local recombinant human insulin-like growth factor-1 (rhIGF-1) application through a biodegradable hydrogel for the treatment of cochleae.

METHODS

A hydrogel immersed with rhIGF-1 was placed on the round window membrane of Sprague-Dawley rats while a hydrogel immersed with physiological saline was applied to control animals. On day 3 after drug application, the animals were exposed to white noise at 120 dB sound pressure level (SPL) for 2 hours. Cochlear function was monitored using measurements of auditory brain stem responses (ABRs) at frequencies of 8, 16, and 32 kHz. The temporal bones were collected 7 or 30 days after noise exposure and the loss of hair cells was quantitatively analyzed.

RESULTS

Local rhIGF-1 treatment significantly reduced the elevation of ABR thresholds on days 7 and 30 after noise exposure. Histologic analysis revealed that local rhIGF-1 treatment significantly prohibited the loss of outer hair cells.

CONCLUSIONS

These findings demonstrate that local IGF-1 application through the biodegradable hydrogel has the potential for protection of cochleae from noise trauma.

Response of cochlear blood flow to prostaglandin E1 applied topically to the round window

CONCLUSIONS

The increase in cochlear blood flow (CBF) after administration of prostaglandin E1 (PGE1) to the round window depends on increased blood flow through the anterior inferior cerebellar artery (AICA).

OBJECTIVES

To evaluate the response of CBF to PGE1 applied topically to the round window, and to investigate the origin of blood flow changes after this topical application.

MATERIAL AND METHODS

The response of CBF to topically applied PGE1 was measured by placing the tip of a laser Doppler probe on the bony wall of the basal turn of the cochlea after the middle ear mucosa over the cochlea had been removed in guinea pigs and rats. In rats, the CBF response to PGE1 administration was investigated after occlusion of the AICA or stapedial artery.

RESULTS

CBF increased following PGE1 administration in both guinea pigs and rats. In rats, CBF increased from 100% to 132%+/-10% (mean+/-SD) after the topical application of 0.5 microl of a 0.014% PGE1 solution. CBF decreased after occlusion of the AICA or stapedial artery but did not increase after PGE1 administration during occlusion of the AICA. The CBF response to PGE1 administration was similar before and after occlusion of the stapedial artery.

Cochlear Preservation After Meningitis: An Animal Model Confirmation of Adjunctive Steroid Therapy

OBJECTIVE/HYPOTHESIS

The objective of the present study was to determine whether treating pneumococcal meningitis with a combined antibiotic and steroid regime will prevent cochlear damage, a common pneumococcal meningitis side effect.

STUDY DESIGN

This was a prospective animal study.

METHODS

Gerbils were randomly assigned to three experimental groups. Animals in group 1, the control animals, received intrathecal saline injections. Animals in groups 2 and 3 received intrathecal injections of Streptococcus pneumoniae to induce meningitis. Although group 2 solely was treated for 7 days with intraperitoneal penicillin injections (48,0000 units), group 3 received, in addition to the antibiotic for 4 days, 0.5 mg/kg intraperitoneal dexamethasone injections. Three months after the meningitis was induced, the animals' cochlear function was determined using auditory brainstem responses (ABRs). Fifteen frequencies were tested, five octaves at three steps per octave between 2 and 50 kHz.

RESULTS

ABR thresholds were significantly elevated only in group 2. When compared with group 1, ABR thresholds were 19 dB higher (P<.05). Frequencies at the low-frequency end of the hearing range were affected more than the midfrequencies. Animals that received dexamethasone had 2-dB higher thresholds than the control group (P>.05).

CONCLUSIONS

Dexamethasone therapy in conjunction with antibiotic therapy preserves cochlear function in cases of S. pneumoniae meningitis in the Mongolian gerbil model.

[Susac syndrome: a report of two cases]

OBJECTIVE

To investigate the clinic characters and diagnosis of Susac syndrome.

METHODS

Two cases were systematically studied by the authors.

RESULTS

All the two cases were young women. The clinical manifestations include acute and subacute multifocal and diffuse encephalopathic symptoms, hearing loss, and visual loss. Diagnosis is facilitated by demonstration of retinal arteriolar occlusions without uveitis or keratoconjunctivitis, mid-to-low frequency unilateral or bilateral sensorineural hearing loss, and numerous small foci of increased signal in the white and gray matter on T2-weighted brain magnetic resonance imaging.

CONCLUSIONS

This rare syndrome often can be identified at an early stage with a careful history and physical examination. MRI, SPECT, retinal fluorescein angiography and audiometry will contribute to diagnosis.

[A new case of Susac syndrome and a review of the literature]

We report a single case of Susac syndrome (microangiopathy of the brain, retina, and cochlea). A 26-year-old woman developed branch retinal artery occlusion in the right eye, associated with bilateral hearing loss that mostly involved low frequencies. MRI of the brain revealed small multifocal hyperintensities in the white matter of the cerebrum on T2-weighted images with gadolium enhancement. The treatment consisted of anticoagulation and antiplatelet drugs. Seventy-one cases of Susac syndrome have been reported in the literature. The Susac syndrome is more frequent in females and its etiology remains unknown. However, immune inflammatory disorders, vasospastic phenomena, and coagulopathy could be involved in its pathophysiology. Treatment options are not standardized, ranging from antithrombotic drugs to immunomodulatory therapy. The course of the disease is self-limited after an initial fluctuating active phase. The prognosis of Susac syndrome is good in most cases.

[Intra-arterial thrombolysis for the treatment of restricted cochlear microcirculation disorder in guinea pigs]

OBJECTIVE

To ascertain a new treatment method for restricted cochlear microcirculation disorder.

METHODS

Photochemical reaction was utilized to induce localized microcirculation damage to the second cochlear turn of every guinea pig. The animals were divided into 5 groups. Group 1 was blank control. Group 2 and Group 3 were injected urokinase (UK) through left subclavian artery or left external jugular vein 30 minutes after photochemical reaction. Group 4 and Group 5 were two control groups. Instead of urokinase, saline injection was applied accordingly.

RESULTS

Both intra-arterial thrombolysis and intravenous thrombolysis were effective to improve the hearing levels and the blood supply to the inner ear. 50 minutes after urokinase injection, animals with intra-arterial thrombolysis showed a lower action potential threshold than that with intravenous thrombolysis (P = 0.025). And this phenomenon lasted 30 minutes. Cochlear blood flow of the animals with intra-arterial thrombolysis began to decrease and action potential began to increase 80-90 minutes after UK injection.

CONCLUSION

Both intra-arterial thrombolysis and intravenous thrombolysis were effective to the restricted thrombosis in the stria vascularis, and intra-arterial thrombolysis showed a better improvement in the early stage of thrombolysis.

The role of acidic fibroblast growth factor in recovery of acoustic trauma

We administered acidic fibroblast growth factor (aFGF) to the perilymph of the guinea pig cochlea after exposure to intense sound to investigate its effect on the process of recovery after acoustic trauma. We assessed auditory brain stem response (ABR) thresholds to evaluate cochlear function and observed the sensory epithelium using confocal laser-scanning microscopy. After noise exposure (120 dB SPL, 5 h), the ABR threshold showed an increase of approximately 50 dB SPL that recovered after 14 days. Cochlear function in aFGF treated ears recovered more quickly than that in control ears. These results suggest that aFGF may play an important role in cochlear recovery after acoustic injury.

[Betaserk efficiency in cochlear and vestibular disorders in the regional surdocenter]

The results are available of the outpatient treatment of 10 patients with cochlear and vestibular disorders with the drug betaserk. The previous treatment was ineffective. Surdological indications for betaserk are described.

[Experimental observation of antagonism of polyaspartic acid against gentamicin-induced phospholipidosis in cochlea of guinea pig]

OBJECTIVE

To observe the effect of polyaspartic acid (PAA) on gentamicin-induced disturbance of phospholipid metabolism in cochlea of Guinea pig.

METHODS

Ninety-four Guinea pigs were divided into 4 groups administered with PAA, PAA + GM, GM, or normal saline respectively. Auditory brain-stem response (ABR) was recorded before and one, five and ten days after the experiment. High performance liquid chromatography (HPLC) was used to determinate the amount of phospholipid in cochlear tissue, and ultrastructural change of lysosomes in the cochlear hair cells was observed by transmission electron microscopy one, five, and ten days after the experiment.

RESULTS

No difference in any indicator was found one day after the beginning of experiment in all groups. The amounts of phosphatidylinositol (PI) and phosphatidylinositol-phosphate (PIP) increased significantly five days after administration of GM (19.7 micrograms +/- 6.6 micrograms and 121 micrograms +/- 21 micrograms respectively). The amount of PIP increased significantly 10 days after administration of GM (126 micrograms +/- 8 micrograms). Transmission electron microscopy showed an increase of number and volume of lysosome in cochlear outer hair cells and appearance of Hensen's body five days after administration of GM. Such changes became more significant and some lysosomes broke in the 10th day. The ABR threshold began to increase 5 days after the administration of GM, and continued to increase with time.

CONCLUSION

PAA has inhibitory effect on gentamicin-induced lysosomal phospholipidosis in cochlea of Guinea pig, thus inhibiting gentamicin-induce hearing loss.

Methotrexate in the management of immune mediated cochleovesitibular disorders: clinical experience with 53 patients

OBJECTIVE

To describe our experience with low dose weekly methotrexate (MTX) in the management of immune mediated cochleovestibular disorder (IMCVD).

METHODS

Between 1991 and 1999, we treated 53 patients with IMCVD with MTX. Patients were selected on the basis of progressive vestibular symptoms that had responded to corticosteroids and in most cases, relapsed. MTX was initiated at a dose of 7.5 mg weekly and increased to doses up to 25 mg weekly as needed. Response was assessed by audiologic studies and history of change in tinnitus and vertigo. MTX was discontinued after 4-6 mo in patients showing no improvement, and after 12-18 mo in patients with improved and stable symptoms.

RESULTS

Three patients were still in early therapy and had not improved. Of the 50 remaining patients, significant improvement was seen in vertigo in 27/39 (69%) patients, hearing loss in 25/47 (53%), and tinnitus in 11/42 (26%). Overall improvement in symptoms was seen in 35/50 (70%) patients. Four patients stopped MTX due to toxicity, and 11 due to lack of response. In 28 patients, MTX was stopped after 12-18 mo when symptoms had stabilized, and restarted in 5 of these after relapse. Seven patients remain on therapy with improved and stable symptoms after 17.3 mo.

CONCLUSION

In this open label experience, a majority of patients with IMCVD improved with weekly low dose MTX therapy with minimal toxicity.

[The Stennert antiphlogistic-rheologic infusion schema in treatment of cochleovestibular disorders]

The pathogenetic mechanisms of acute cochleo-vestibular lesions are still unknown, but viral infections and vascular phenomena with impairment of microvascular perfusion are thought to play a major role. Between 1 July, 1986 and 28 February 1998, 1501 patients were treated with an infusion protocol using cortisone, dextrane 40 and pentoxifylline. Group 1 contained 1001 patients with sudden hearing loss, group 2a 107 patients with isolated tinnitus and group 2b 393 patients with labyrinthine disorders (among which were 81 patients with cochleovestibular dysfunction). The records were evaluated retrospectively. In group 1 complete hearing recovery occurred in 44.8%, partially in 40.4%, no change in 12.1% and worsened in 2.6%. In group 2a with isolated tinnitus 17.9% had a complete recovery, 43.9% partial recovery, 35.5% no change and 2.8% worsened symptoms. In group 2b vertigo disappeared in 56.8%, had partial recovery in 21.0% and did not change in 7.4%. In the 1501 patients treated, no significant side-effects were found to the medical interventions used. From these results we conclude that the infusion protocol is safe and effective in the treatment of cochleo-vestibular disorders.

Effects of immunosuppression on the development of cochlear disease in the MRL-Fas(lpr) mouse

OBJECTIVES

The MRL-Fas(lpr) mouse, an animal that spontaneously develops multisystemic autoimmune disease, has been proposed as model of immune-mediated inner ear disease. Previous studies revealed that this mouse manifested elevated auditory brainstem response thresholds, hydropic degeneration of strial cells, and antibody deposition within strial capillaries. As the etiology of the observed strial disease may be immune, genetic, or uremic, a study was designed to attempt to delineate between these possible etiologic factors.

STUDY DESIGN

Prospective, controlled animal study.

METHODS

Dexamethasone, which is known to suppress autoantibody production and glomerulonephritis in these animals, was administered systemically on a daily basis to experimental animals, beginning at 6 weeks of age. Control animals received no treatment. Animals were allowed to age, with control animals predictably manifesting systemic disease at 20 weeks of age, at which point all animals were sacrificed.

RESULTS

Animals receiving dexamethasone treatment manifested a significant reduction in serum immunoglobulin levels, lymphoid hyperplasia, and a significant improvement in the level of renal function. However, morphologic analysis revealed a persistence of strial disease despite the elimination of strial antibody deposition.

CONCLUSION

The results of this experiment support the hypothesis that genetic mechanisms may be responsible for the observed strial disease. Further studies are under way to confirm these findings.

New approaches for inner ear therapy with glutamate antagonists

In the mammalian cochlea neurotransmission between inner hair cells and afferent auditory neurons is probably mediated by glutamate or another related excitatory amino acid. Neurotoxicity induced by excessive glutamate release seems to play a crucial role in some pathological conditions of the cochlea, such as ischaemia or noise trauma. Thus, glutamate antagonists may be a new therapeutic strategy for different inner ear diseases. Because of their potential severe side-effects only a few glutamate antagonists have so far been adopted for clinical use. We used microiontophoretic techniques to compare the effects of memantine and caroverine on the glutamatergic transmission of inner hair cells of the guinea pig and tested the possibility of a local administration of memantine to the cochlea with a micropump. Memantine selectively inhibited the NMDA (N-methyl-D-aspartate) stimulated activity while caroverine blocked NMDA as well as AMPA (alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid) induced activity of inner hair cell afferents. With a flow rate of 1 microl/h the local administration of memantine via a cochleotomy was succeeded in a reversible blockade of the spontaneous and the NMDA induced firing of inner hair cell afferents. These results suggest that local application to the cochlea could be a feasible way to administer glutamate antagonists in sufficient amounts while avoiding systemic side-effects.

[The use of betaserk in patients with cochlear-vestibular disorders]

20-year experience with 220 cases of cochleovestibular disorders treated with betaserk shows high efficacy of this drug in the above patients, especially at initial stages of Meniere's disease. Betaserk is recommended for wide outpatient practice.

[Effect of Fucong tablets and its ingredients on ototoxicity of gentamycin in guinea pigs]

OBJECTIVE

To assess the antagonistic effect of Fucong Tablet (FCT) and its ingredients on ototoxicity of gentamycin in guinea pigs.

METHODS

The guinea pigs were given gentamycin 80 mg/kg intramuscularly once daily for 20 days and FCT or its ingredients separately oral taken for 20 days. The auditory brain stem evoked response (ABR) threshold, vascular stria blood circulation condition, outer hair-cell count and cochlear ultrastructure of guinea pigs were observed before and after treatment to assess the antagonistic effect and protective effect of FCT on cochlear structure.

RESULTS

FCT and its ingredients of tonifying Kidney, replenishing Qi and blood, promoting blood circulation could lower the impairment ratio of outer hair-cell induced by gentamycin (P < 0.05), protect morphosis and function of cochlea and lower the elevated ABR threshold (P < 0.05).

CONCLUSIONS

FCT and its ingredients could reduce the toxic damage on ear induced by gentamycin effectively.

Osmotic drugs in the treatment of cochlear disorders: a clinical and experimental study

On the grounds of positive results obtained with Meniere's patients, agents such as glycerol and mannitol have been included in the therapeutical protocol of other cochlear disorders presenting with hearing loss either of sudden onset, but not observed at an early stage, or accompanied by tinnitus and aural pressure. Intravenous infusions of either 10% glycerol or 18% mannitol were given to selected patients 3 to 6 times with a time interval of 1 to 3 days. Hearing loss, tinnitus and aural pressure were evaluated as improved, unchanged or worsened. In 33% of the glycerol group and 23.8% of the mannitol group we observed hearing threshold improvement, while aural fullness improved in 45% of the glycerol and 56.2% of the mannitol groups, and tinnitus was only relieved in 13.1% of the glycerol and 5.8% of the mannitol group. A parallel experimental study was carried out on guinea-pigs in order to shed light on the effects of mannitol and glycerol on the inner ear. Cochlear blood flow was measured with a laser Doppler flowmeter at the level of the basal turn of the cochlear lateral wall, both in normal and hydropic guinea-pigs, before and after osmotic intraperitoneal infusion. Basal values in the normal cochlea were much higher than in the hydropic one, and both mannitol and glycerol markedly influenced the local blood flow in the normal cochlea, giving few or no changes in the hydropic one.

Methotrexate management of immune-mediated cochleovestibular disorders

Immune-mediated cochleovestibular disorders continue to present a management challenge to the otolaryngologist. The traditional treatment of these disorders, corticosteroids and/or cyclophosphamide (Cytoxan), has been associated with serious and occasionally life-threatening complications. In this study we report our experience in treating 25 patients with immune-mediated cochleovestibular disorders with methotrexate, a less toxic immunosuppressive agent that has been used extensively in patients with rheumatoid arthritis. Mean duration of treatment was 12.9 months, and adverse reactions were acceptable and reversible. Hearing improved in 69.6% of patients, and vestibular symptoms subsided or improved in 80% of patients. The results of this study suggest that methotrexate treatment is effective in a substantial number of patients with immune-mediated cochleovestibular disorders and has acceptable adverse reactions. A prospective, randomized study is needed to compare the efficacy of methotrexate with that of other immunosuppressive agents.

ENT manifestations of relapsing polychondritis

Relapsing polychondritis is a rare disease probably of auto-immune etiology comprising inflammatory involvement of cartilage as well as phenomena of vasculitis. ENT manifestations are frequent and the authors present a case involving chondritis of the auricle, the nasal septum and affecting the cochleo-vestibular system as well. The diagnosis is based on the evocative clinical picture and on histological confirmation. Treatment consists of corticosteroids and immunosuppressive agents.

Otosyphilis: diagnostic and therapeutic update

The thorough investigation of patients presenting with sudden or fluctuating hearing loss, ringing or vertigo includes serology to exclude otosyphilis. Treatment of otosyphilis with penicillin and corticosteroids has achieved improvement in hearing, tinnitus and vertigo, but not in all patients. Selecting which patient with positive serology will benefit from treatment remains a difficult clinical problem. All patients presenting to The New York Eye and Ear Infirmary with cochleovestibular dysfunction of unknown aetiology and positive syphilis serology were assumed to have otosyphilis and were treated with intravenous penicillin, if non-allergic, and steroids. Lumbar puncture and HIV testing were performed. Eighteen patients were treated. Hearing (SRT and/or discrimination) improved in 4 of 16 patients with hearing loss (25%), tinnitus decreased in 10 of 14 (71%) and dysequilibrium improved in 6 of 9 (66%). Factors associated with a good response included fluctuating symptoms, especially hearing, hearing loss less than five years, and age less than 60. Improvement was unrelated to the severity of the loss or previous therapy. Patients with CSF abnormalities, including two patients with HIV disease, had subjective improvement. A summary of our results and a treatment protocol are presented.

[Trimetazidine therapy in atrio-cochlear disturbances of vascular origin]

Therapeutic effects of TMZ treatment were evaluated in 31 patients with atrio-cochlear disorders caused by an insufficiency of cerebral circulation. It was found that the results of vestibular or cochlear disorders remission was dependent on the time interval between the onset of symptoms and the beginning of trimetazidine therapy. The best results were also found in patients suffering from atrio-cochlear disorders lasting not longer than two years and due to arterial hypertension or cerebral basilar artery insufficiency.

Otosyphilis: a diagnostic and therapeutic dilemma

Traditional treatment of otosyphilis with penicillin and corticosteroids has achieved hearing improvement; however, selecting which patients with a positive fluorescent treponemal antibody absorption (FTA-ABS) test will benefit from treatment remains a problem. In order to study this problem, 18 patients with cochleovestibular dysfunction of unknown etiology and positive syphilis serology were treated with intravenous penicillin and corticosteroids. In addition, lumbar puncture and human immunodeficiency virus (HIV) testing were performed on all patients. Hearing improved in 5 (31%) of 16 patients, tinnitus decreased in 11 (85%) of 13, and vertigo improved in 6 (86%) of 7. Factors associated with hearing improvement were hearing loss present less than 5 years, fluctuating hearing, and age less than 60. Improvement was unrelated to the severity of the loss or previous therapy. All patients with cerebrospinal fluid abnormalities, including two patients with HIV disease, had subjective improvements. A diagnostic and treatment protocol is presented.

Experimental basis for lidocaine therapy in cochlear disorders

In order to further our basic understanding of the effects of lidocaine hydrochloride in the inner ear, cochlear potentials and blood flow (CBF) were assessed after intravenous (i.v.), anterior inferior cerebellar artery (AICA), and local round window (RW) lidocaine administrations in guinea pigs and rats. Lidocaine RW applications produced a dose dependent decrease in compound action potentials (CAP) and cochlear microphonics (CM). The sensitivity changes were more pronounced at high frequencies. These findings suggest that lidocaine has specific pharmacological action in the inner ear other than simple anesthesia of the auditory nerve. The basal turn endocochlear potentials (EP) were not altered by topical lidocaine, implicating altered organ of Corti function following local application of lidocaine. RW applications of lidocaine had no effect on CBF or systemic blood pressure (BP). I.v. infusions caused substantial reductions in BP. In the case of systemic infusions the percent changes in CBF were equal to and accountable by the BP changes. The microinfusions (50 mg/ml, 100 nl/min) through AICA produced a 30%, long lasting increase in CBF. However, neither systemic lidocaine nor AICA infusions had an effect on CAP or CM. These findings indicate that systemically given lidocaine may not cross the blood-cochlear barrier and that the cochlear electrophysiological effects due to lidocaine when given locally are partly mediated by direct influence on cochlear hair cell function; they also suggest that lidocaine-induced interference with active ion transport in the lateral wall or an influence on CBF are not contributing factors.

[Itching following therapy with hydroxyethyl starch (HES) in otoneurological diseases]

It is generally assumed, that a disturbance of microcirculation is the common pathogenetic end factor in various cochleovestibular disorders of different etiology. Therefore improvement of microcirculation is an important therapeutic goal. Several studies demonstrated, that hydroxyethylstarch (HES) has better haemorheological effects than Dextran and less side effects. For this reason we have changed the therapy with Dextran since 1987 to hydroxyethylstarch in several oto-neurological disorders (as sudden hearing loss, neuronopathia vestibularis, idiopathic facial palsy). As after the therapy with HES--generally after dismissal from the ENT-department--some patients complained of general pruritus, so we performed a retrospective study with a standardized interview-protocol. Of 481 treated patients we investigated 237 (49%): of 149 patients treated with HES 200/0.5, 43 patients (28.8%) complained of pruritus; from 88 patients treated with Dextran 40, only 5 patients (5.7%) reported pruritus. The difference is significant (p less than 0.0001). In nearly half of the patients (more than 40%) the pruritus started in normal skin 1 to 3 weeks after the HES-therapy and lasted for 6 weeks to 6 months; the itching was very resistant to therapy (f.e. with antihistaminics). We want to draw the attention to this possible, in the literature until now quite neglected, for some patients extremely uncomfortable and socially embarrassing side effects after HES-therapy when given in relatively high doses. It is therefore suggested therapeutic recommendations should be developed to prevent this undesired side effect.

[Evaluation of effectiveness of treatment of cochleovestibular disorders with mildronate]

The results of mildronate treatment of 67 patients with acute (23 patients) and chronic (44 patients) cochleovestibular disorders of different origin are discussed. The efficacy was evaluated in terms of subjective reports and objective parameters. The therapy proved effective in 53 (79.1%) patients, out of which it was good in 30 (44.8%) patients and satisfactory in 23 (34.3%) patients. The therapeutic results were better in patients with acute cochleovestibular dysfunction: good results were seen in 86.9% patients. In patients with chronic cochleovestibular dysfunction good results were recorded only in 75.0% patients. It is concluded that mildronate can be effectively used to treat patients with cochleovestibular disorders.

[Use of monotreane in the treatment of patients with cochleovestibular disorders]

Patients with cochleovestibular disorders of central and peripheral origin were treated with monothreane (produced by Luitpold Werk, FRG). The drug was given to 70 patients (19 men and 51 women) at the age of 28 to 64 years, 28 patients of which had disorders of peripheral origin and 42 patients disorders of mixed origin. The patients were examined by clinical methods and special tests and hypertension was diagnosed in 32 patients. The therapy yielded good effects in 61 patients: complete recovery of vestibular disorders was seen in 28 patients and relief of headaches in 42 subjects. Side effects were observed in nine patients who showed reduction of perception thresholds which disappeared after drug withdrawal. Monothreane had a beneficial effect on the course of the hypertensive disease.

Electronystagmographic findings and recovery of cochlear and vestibular function in patients suffering from sudden deafness with a special reference to the effect of anticoagulation

The study included 80 patients treated for sudden deafness over the last 5-7 years. Case history, laboratory findings, pure-tone audiogram and electronystagmography (ENG) findings were noted. If any abnormalities had been recorded in ENG studies, the studies were redone. ORL status was redefined and audiograms were obtained in all patients. When becoming ill, the 80 patients had not differed from the normal population in common cardiovascular risk factors. None of them had had signs of viral infection (paired serum samples had been taken at 2-week intervals; routine examinations had been done for common viral antigens). As many as 31 of the 80 patients with acute hearing loss had had abnormalities such as spontaneous nystagmus (PN), hypoexcitability (HE) and directional preponderance (DP) in the bithermal caloric tests (+44 degrees C, + 30 degrees C) of their ENG studies. Twenty of the 31 patients still had abnormal ENG studies after 5-7 years. Only 1 subject had positional nystagmus, and none had subjective vertigo. Patients with an abnormal ENG study showed a poor recovery of the speech reception threshold, whereas those with a normal ENG study showed slightly significant (p less than 0.05) recovery.