Current clinical and pathological features of round window diseases

Effect of acute inner ear pressure changes on low-level distortion product otoacoustic emissions in the guinea pig

OBJECTIVE

To determine a relation between acute inner ear pressure changes and cochlear function as measured by low-level 2f(1)-f(2) distortion product otoacoustic emissions (DPOAEs).

MATERIAL AND METHODS

During and after a change in inner ear pressure induced by injection or aspiration of perilymph, the 2f(1)-f(2) DPOAE at 4.5 kHz generated by low-level primaries was recorded in the guinea pig.

RESULTS

Large changes in overall inner ear pressure produced only small changes in the 2f(1)-f(2) amplitude and phase. During injection of 0.5 microl of artificial perilymph into the scala tympani over a 10-s period, the mean inner ear pressure increased by approximately 500 Pa, with an accompanying mean increase in the 2f(1)-f(2) amplitude of 0.7 dB. During aspiration of 0.5 microl of perilymph over a 10-s period, the mean inner ear pressure decreased by approximately 700 Pa, with an accompanying mean decrease in the 2f(1)-f(2) amplitude of 0.9 dB. Changes in DPOAE amplitude followed inner ear pressure changes with a delay of 1-2 s. The magnitude and sign of the amplitude changes can (partly) be explained by a change in oval window stiffness. No explanation was found for the measured delay.

CONCLUSION

Clinically, these experiments can be of value in gaining insight into the pathophysiological mechanisms of pathological pressure changes as seen in Meniere's disease and perilymphatic fistulae.

Episodisch auftretendes Schwindelgef�hl

While an acute loss of unilateral vestibular function (for example in case of neuritis vestibularis or temporal bone fracture) leads to long-term vertigo, this paper deals with the phenomenon of episodic vertigo (duration: seconds up to hours).Both peripheral-vestibular and central disturbances can be responsible for this symptom. The aim of this paper is to present otological and neurological diseases which can lead to episodic attacks of vertigo.

Meniere's disease: overview, epidemiology, and natural history

Meniere's disease is a disease of the inner ear characterized by a triad of symptoms: vestibular symptoms, auditory symptoms, and pressure. The pathologic correlate of Meniere's disease is endolymphatic hydrops and the etiopathogenesis involves a deficiency in the absorption of endolymph. The pathophysiology of the symptoms is still disputed: membranous ruptures, pressure and mechanical displacement of the end organs, or obstruction followed by an abrupt clearance of the endolymphatic duct. The course of the disease may be progressive or nonprogressive and, in addition to the typical presentation of Meniere's disease, two variations of the disorder have been identified: cochlear Meniere's disease, and vestibular Meniere's disease. It can be further broken into two subsets: Meniere's syndrome, with a known and well-established cause, and Meniere's disease, in which the cause seems to be idiopathic. It is likely that there are racial (genetic) as well as environmental factors that influence differences in incidence among countries and among various sections of countries. The disease is much more common in adults, with an average age of onset in the fourth decade, the symptoms beginning usually between ages 20 and 60 years. Meniere's disease is (grossly) equally common in each sex, and right and left ears are affected with fairly equal frequency. The diagnosis of Meniere's disease is by exclusion, and a careful history is the most important guide to a correct diagnosis. Its medical treatment is largely empiric. Surgery can be considered when, even after medical therapy, the disease progresses and the symptoms become intractable. Surgery may be either conservative or destructive. Bilaterality must be considered when deciding the best surgical option for a patient with Meniere's disease. It is the authors' opinion that endolymphatic sac surgery is an extension of conservative treatment.

Diagnosis of Meniere's disease: routine and extended tests

Meniere's disease can compromise the quality of life of some patients in a manner so seriously that it can cause social segregation, even from family. Hearing loss, tinnitus, aural pressure, and disturbances in equilibrium added to an emotional instability frequently present in these patients may take them to a progressive state of solitude and depression, marking their lives by personal tragedy and making life a living hell. The clinical picture of Meniere's disease fluctuates, however. Individually, subsidiary examinations become impotent in diagnosing Meniere's disease. To be called Meniere's disease, the cause must be unknown; otherwise it would constitute Meniere's syndrome. Taking all of this into consideration, one would call this an unusual situation, or at least confusing. The lack of an etiologic diagnosis in medicine always creates anxiety for doctors and patients. What is considered to be either a routine or an extended test may change from service to service. The physician does not need to order all tests. What the physician needs is a protocol he or she trusts. Test results can vary, even depending on the moment when they are performed. More important than the number of tests ordered is the strategy by which the tests should be put together at that certain moment. The authors believe that one should have his or her own protocol for diagnosis, always beginning with a detailed history taking being guided by them most of the time. It is the authors' understanding that patients with Meniere's disease should be followed closely by their ear, nose, and throat doctor in episodes of vertigo or fluctuation of their hearing, tinnitus, or aural pressure. Should the patient be experiencing a stable period, a clinical visit along with an audiovestibular workup should be performed at least once a year. By monitoring the course of the disease, clinicians would be able to detect early changes in symptoms and/or test results, giving them the possibility to intervene clinically as early as possible in acute episodes of vestibulocochlear disorganization, protecting the inner ear, and minimizing sequelae from spells of hydrops. The authors believe that only the association of clinical sense and as many subsidiary tests as are useful will lead to a desirable level of certainty in the diagnosis of Meniere's disease, and will allow clinicians to presume bilateral involvement, monitor the development of the disease, intervene in its natural course, and idealize appropriate treatment.

Sensorineural hearing loss in chronic otitis media

Although many studies have demonstrated an association between chronic otitis media (COM) and sensorineural hearing loss (SNHL), there still remains disagreement about the relationship. A retrospective study was conducted to examine the relationship between sensorineural hearing loss and chronic otitis media. Forty-one patients met the following criteria: unilateral COM and no history of head injury, meningitis or previous otological surgery. The differences in preoperative bone conduction threshold between diseased and control (contralateral normal) ear were statistically significant (P < 0.01) and varied from 5.24 to 9.02 dB across the frequency range. The effect of duration of disease on the degree of SNHL was also analysed but no correlation was found. The presence of cholesteatoma and/or ossicular erosion was not associated with a significantly increased risk of sensorineural hearing loss.

Bacterial cytolysin perturbs round window membrane permeability barrier in vivo: possible cause of sensorineural hearing loss in acute otitis media

The passage of radioiodinated streptolysin-O (SLO) and albumin through the round window membrane (RWM) was studied in vivo. When applied to the middle ear, SLO became quantitatively entrapped in this compartment and no passage to the cochlea occurred. However, flux of radioiodinated albumin through the toxin-damaged RWM was observed. We propose that the passage of noxious macromolecules, such as proteases, from a purulent middle-ear effusion may be facilitated by pore-forming toxins, resulting in cochlear damage and sensorineural hearing loss.

Breakdown of the round window membrane permeability barrier evoked by streptolysin O: possible etiologic role in development of sensorineural hearing loss in acute otitis media

Sensorineural hearing loss is a common sequela of acute and chronic otitis media, and the round window membrane (RWM) is currently being considered as a major route for noxious agents to pass from the middle ear cavity to the cochlea. Streptococcus pneumoniae, a major causative agent of otitis media, and Streptococcus pyogenes A produce molecularly related toxins, pneumolysin and streptolysin O (SLO), that form large pores in target membranes. In this study, we analyzed the effects of SLO on the permeability of the RWM. Resected RWMs from a total of 104 guinea pigs were embedded between two chambers of an in vitro system. One chamber was designated as the tympanal (cis) compartment, and the other was designated as the inner ear (trans) compartment. The permeability of normal and SLO-damaged RWMs towards Na+, [14C]mannitol, and proteins was investigated. SLO evoked permeability defects dose dependently in the RWM with fluxes of both Na+ and [14C]mannitol being demonstrable over a time span of up to 8 h. Serum proteins and radioiodinated SLO were also shown to pass through the damage RWM. Scanning electron microscopy revealed the morphological correlates to these results. We propose that damage to the RWM by potent pore-forming cytolysins leads to leakage of ions from the perilymph. Ionic disequilibrium and passage of noxious macromolecules to the cochlea could contribute to disturbances of the inner ear function.

The effects of experimentally increased perilymphatic pressure on click-evoked otoacoustic emissions in guinea pigs

We used the IL088 Otodynamic Analyzer system to study click-evoked otoacoustic emissions (CEOAEs) in 30 healthy guinea pigs. The animals were anesthetized and patterns of the CEOAEs were evaluated before manipution, after the tympanic bulla was opened, and after formation of a microfistula on the basal turn of the cochlea. The animals then were divided into three pressure loading groups (10, 20, and 30 cm H2O). CEOAEs were recorded with a capillary manometer at pretest, 5, 10, 20, 30, 45, and 60 min after perilymphatic pressure loading to the basal turn of cochlea, and 10 and 20 min after pressure unloading. As perilymphatic pressure increased, all three pressure groups showed maximum decreases in both echo response and reproducibility 5 min after pressure loading. In the 10 cm H2O pressure group, emissions recovered 10 min after pressure loading, and this tendency continued. However, in the 20 and 30 cm H2O pressure groups, no recovery of emissions was seen throughout the 60 min observation period, except for emissions after pressure unloading. The results suggest that the echo response and reproducibility may be sensitive indicators of cochlear function and perilymphatic pressure regulation capacity.

Surgical advances in treating otitis media

Surgical methods of treating otitis media and its sequelae are discussed, according to the classification of otitis media presented in an earlier report. Surgical management of otitis media with effusion and recurrent purulent otitis media includes myringotomy and use of ventilation tubes. Occasionally, otitis media with effusion will lead to structural and other pathologic changes in the middle ear, and conservative treatments such as use of medication or tubes will not suffice. Indications and methods for exploratory tympanotomy and reconstruction of the middle ear are discussed. In such instances, tympanoplasty can be used to the patient's benefit. Chronic otitis media with mastoiditis, defined by the presence of intractable pathologic tissue, generally requires surgical correction. Classic methods include simple mastoidectomy, modified radical (Bondy) mastoidectomy, and radical mastoidectomy. Current classifications of procedures would also include closed-cavity tympanomastoidectomy, open-cavity tympanomastoidectomy, and intact-bridge tympanomastoidectomy (a combined approach). The diagnostic and surgical approach to silent or subclinical otitis media is discussed. Diagnosis and treatment of sequelae of otitis media, including sequelae in the middle ear and, less commonly, in the inner ear, are discussed.

Hyaluronan applied to lesioned round window membrane is free from cochlear ototoxicity

Hyaluronan (HYA) in 1% solution was instilled into the round window (RW) niche of rats (n = 6) prior to perforating the round window membrane (RWM). Cochlear functioning and structure were then monitored by recording auditory brainstem responses (ABRs) at 2-31.5 kHz and by scanning electron microscopy. Perforation of the RWM alone (n = 6) resulted in immediate loss of ABR thresholds between 6 and 31.5 kHz in 2 of 6 animals. Similar results were obtained after instilling HYA into the RW niche and subsequent RWM perforation (n = 6). After 2 months, ABR thresholds were recorded at all frequencies in the HYA-treated animals, whereas in 2 of the controls no ABR thresholds could be elicited at 20 and 31.5 kHz. However, in both treatment groups the mean ABR thresholds and mean latencies for wave II at the ABR threshold returned to the pre-surgical (normal) range after 2 months. With respect to the cochlear morphology the results in both treatment groups were also alike including minor structural changes in hair cell stereociliae but no loss of hair cells. It is concluded that HYA, when instilled into the middle ear with the inner ear opened, is free from cochlear otoxicity.

Sensorineural hearing loss in chronic otitis media

A statistical study was done on the sensorineural component in hearing loss, using 595 patients suffering from Chronic Otitis Media (COM); of these, 195 with monolateral COM were taken into consideration. They presented criteria of valuation which excluded other possible causes of sensorineural hearing loss, such as exposure to acoustic trauma, ototoxic drugs, cardiovascular disease, past head injury and hereditary causes. The contralateral (healthy) ear served as a control. We determined the average sensorineural component in the hearing losses in relation to the age of onset and duration of the disease, examining it in relation to other eventual aural complications such as cholesteatoma. On the basis of the data obtained, we believe that the sensorineural component in hearing loss does not change with respect to the age of onset of COM, but the duration of COM does exert a significant influence.

Perilymphatic hypertension

A syndrome termed perilymphatic hypertension is described as being seen in a small subset of patients with sudden sensorineural hearing loss. A patent or semipatent cochlear aqueduct or modiolus are considered precursors to this condition. Perilymphatic hypertension is believed to predispose to perilymphatic fistula, which may be part of the process of resolution. The pathogenesis for perilymphatic hypertension and fistula are hypothesized and discussed. Treatment for this subset of patients consisted of paracentesis of the round window membrane followed by grafting, with improvement of hearing in certain patients. In no instance did hearing subsequently decrease.

Survey of interactions between middle ear and inner ear

Diseases with interaction between the middle ear and inner ear include 1) congenital anomalies, 2) trauma, 3) infection/inflammation, 4) tumors, 5) granulomas, 6) ototoxic eardrops, 7) cochlear implants, 8) otosclerosis, 9) Meniere's disease-decompensated, and Meniere's disease with perilymphatic fistula, and 10) perilymphatic hypertension. Clinical and pathological characteristics are briefly categorized in this survey. The clinical utility of exploratory tympanotomy in diagnosis and treatment of middle ear pathology and middle ear/inner ear interactions is commented upon.