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Purpose: The purpose of this study was to describe the role of explorative tympanotomy in patients with Profound Sudden Sensorineural Hearing Loss (SSNHL) without clinical evidence of perilymphatic or labyrinthine fistula and to compare intraoperative findings with the postoperative hearing outcome., Study Design: Retrospective study of all patients diagnosed with SSNHL who underwent explorative tympanotomy between 2002 and 2005., Settings: Tertiary care university-affiliated hospital., Subjects and Methods: Eighty-two patients were diagnosed with unilateral profound SSNHL and underwent tympanotomy with sealing of the round and oval windows. Values of pure tone audiograms and percentage hearing loss of patients with and without intraoperative diagnosed perilymphatic fistula (PLF) were compared and analyzed., Results: PLF was diagnosed in 28% cases intraoperatively. In most cases, hearing improved significantly after surgery. Interestingly, patients with PLF had a 2.4 times greater decrease of percentage hearing loss compared to patients without PLF., Conclusions: Explorative tympanotomy seems to be useful in patients with profound SSNHL. Patients with PLF benefit more from the surgical procedure and have better outcome than patients without PLF., (Copyright © 2017 Elsevier Inc. All rights reserved.)

We report a 63-year-old man who developed transient acute on chronic hearing loss after a lumbar puncture performed to investigate raised intracranial pressure. He was subsequently found to have stenosis of the distal left transverse sinus, which was treated with stenting., (Copyright (c) 2009 Elsevier Ltd. All rights reserved.)

Objective: There exist 3 communication routes between the intracranial space and the inner ear, the vestibular aqueduct, the cochlear aqueduct, and the internal auditory canal. They possess a key role in inner ear pressure regulation and fluid homeostasis and are related to inner ear diseases., Review Methods: Relevant literature was reviewed, and the current knowledge of the anatomy, physiologic importance, and relations to inner ear diseases were described. Pathologic communication routes such as semicircular canal dehiscence syndrome were highlighted as well., Conclusion: Abnormalities in all 3 communication routes may predispose or be the cause of distinct inner ear pathologic condition and involved in other cochlear and vestibular syndromes, in which their role is not completely clear. The increasing knowledge of the underlying mechanisms encourages promising approaches for possible intervention in the future.

There are a variety of causes of otorrhea in children. The most important factor in reaching the proper diagnosis and providing relief of the problem is aural toilet. Once adequate debridement has been performed, the diagnosis is usually clearer, and treatment with ototopicals is significantly more effective. Most cases of otorrhea are due to infection or granulation tissue and can be managed initially with appropriately selected ototopical medication, thereby avoiding the risks and side effects of systemic therapy and the need for referral to a specialist. However, otorrhea in children that is refractory to medical therapy may be due to retained tympanostomy tubes or insidious pathology such as cholesteatoma or malignancy. In such cases, prompt referral to the otolaryngologist can facilitate accurate diagnosis and successful management.

Perilymphatic fistula (PLF) is often difficult to diagnose because of the similar symptomatology, such as vertigo, tinnitus and hearing loss, which is found in several inner ear diseases. We attempted to correlate a positive result of low frequency sound (LFS) stimulation tests in posturography with the presence or absence of a PLF confirmed by transtympanic endoscopy in 209 patients with various inner ear diseases (Meniere's disease ( n=128), vestibulopathy ( n=41), cochleopathy ( n=28) and sudden deafness ( n=12). LFS provoked unsteadiness in posturography without PLF in 24 patients with Meniere's disease, in 5 patients with vestibulopathy, in 3 patients with cochleopathy and in 2 patients with sudden deafness. In one patient, tympanoscopy revealed fistula in the round window membrane that was covered with a fibrinous layer. In four cases there was abnormal light reflex in the round window but without PLF. In eight cases, Hennebert's sign was present with nystagmus, without PLF. We conclude that pathological responses to the LFS test in posturography can also be encountered in other inner ear diseases without PLF.

It has previously been demonstrated that ototoxicity induced by systemic administration of cisplatin is reduced by concomitant systemic administration of alpha-melanocyte stimulating hormone (alpha-MSH). In this study we investigated the effects of cochlear, perilymphatic application of alpha-MSH during intraperitoneal administration of cisplatin. Guinea pigs, implanted with a round-window electrode, allowing daily monitoring of the compound action potential (CAP), and also implanted with a mini-osmotic pump, pumping at a rate of 0.25 microl/h either physiological saline or alpha-MSH solution (0.02, 2, and 20 microg/ml), were treated daily with a bolus injection of cisplatin (2 mg/kg) until the electrocochleogram showed a persistent decrease in CAP amplitude (> or = 40 dB threshold shift at 8 kHz). Then, cisplatin treatment was stopped, but intracochlear perfusion of alpha-MSH or physiological saline was continued for 10 days to evaluate possible effects of alpha-MSH on the expected recovery. On day 10, the animals were killed and the cochleas were fixed and processed for histological analysis. All groups required 6-7 days of cisplatin to reach the criterion CAP threshold shift. Ten days after cessation of the cisplatin treatment, recovery of the CAP was observed in all groups and at all frequencies, although it was more pronounced at the lower frequencies. With respect to recovery, small statistically significant differences were found between the saline and the alpha-MSH co-treated groups. Histological results showed significantly less outer hair cell (OHC) loss in the group co-treated with 2 microg/ml alpha-MSH as compared to the group co-treated with saline. Since alpha-MSH was directly delivered to the cochlea, the ameliorating effect of alpha-MSH on OHC survival is likely to involve a cochlear target.

Dizziness and vertigo are common complaints in patients referred for neurological evaluation. With a basic understanding of vestibular physiology and proper examination techniques, a correct diagnosis can generally be made at the bedside. This article reviews the most common peripheral and central vestibular syndromes as well as the key elements of the bedside vestibular system examination.

Objective: Endoscope-guided round window membrane repair was performed to evaluate whether the approach is feasible in the treatment of a round window fistula., Study Design: Retrospective case review., Setting: Tertiary care academic center., Patient: A 27-year-old man had been scuba diving 6 days previously in the Australian Great Barrier Reefs. He had poor hearing with tinnitus in the left ear and a vertiginous sensation., Intervention: A myringotomy was incised, and a tympanoscope was introduced into the middle ear cavity. With the patient under general anesthesia, the middle ear and the oval and round window areas were examined with a tympanoscope. In endoscopic visualization, a round perforation could be seen in the round window membrane. After detection of the round window perforation, a small piece of temporal fascia was obtained to seal the membrane perforation., Results: One month after the operation, the patient's hearing was significantly better. The myringotomy had healed., Conclusion: A transmyringeal endoscopic procedure for round window fistula repair is feasible and combines the best features of minimally invasive surgery and aural endoscopy.

The aim of the study was to detect inner ear fluid pressure changes induced by glycerol in Menière's disease (MD) by means of a tympanic membrane displacement analyser (TDA). The study group consisted of 25 MD patients. The Vi (maximum inward displacement of the tympanic membrane) and the Vm (mean displacement of the tympanic membrane) were measured at 10, 20 and 25 dB above the stapedial reflex threshold. Each patient received therapy based on glycerol. The control group consisted of 20 patients with non-hydropic sudden hearing loss. At 20 and 25 dB above stapedial threshold MD patients had lower Vi values before therapy. After glycerol, we observed a Vi increasing in the hydropic ears in 68-96 per cent of patients. Since a Vi improvement implies a reduction of perilymph pressure, our results confirm the effectiveness of Vi in detecting specific action of glycerol in MD.

Objective: The aim of this study was to determine the dimensions of cochlear aqueduct radiologically in patients with Ménière's disease and in normal subjects, and to correlate these findings with normal and low static acoustic compliance (SAC) (high and normal perilymphatic pressure) to see whether the dimensions of the cochlear aqueduct play any role in the perilymphatic pressure in normal individuals and patients with Ménière's disease., Study Design: Prospective double-blind study., Setting: The study was conducted at Hacettepe University Medical Faculty, a tertiary care center., Patients: Forty patients with Ménière's disease with bilateral involvement, diagnosed by vertigo attacks, fluctuating hearing loss, tinnitus, fullness in the ear, and cochlear sensitivity constituted the patient group. Forty healthy individuals with no otolaryngologic symptoms constituted the control group., Interventions: All individuals underwent SAC measurement in terms of equivalent volume in milliliters, based on two volume measurements. To measure the dimensions of the cochlear aqueduct, high-resolution computed tomography of the temporal bone in the axial plane was performed., Results: There was no statistically significant difference in the width of the cochlear aqueduct between patients with Ménière's disease and normal subjects. When SAC measurements were also taken into account, there was no difference in cochlear aqueduct dimensions between individuals with normal and low SAC values in the two groups., Conclusion: The dimensions of cochlear aqueduct are not significantly different in Méniére's disease patients and normal individuals. Also, the cochlear aqueduct does not appear to play a significant role in normal and low SAC values in the two groups of individuals.

The examination of 120 patients with verified labyrinthine fistulas (LFs) has demonstrated that perilymphatic LFs most often are caused by rupture of the cochlear window's membrane (54%). Among other reasons were broken base of the stapes (6%), the defect in the area of both windows (17%), rupture of the annular ligament of the stapes (15%), defects in the area of semicircular canals. Incompetence of the stapedial piston prosthesis is documented.

The MMS-10 Tympanic Displacement Analyser is a new device for measuring perilymphatic pressure in humans. This instrument was used in 70 patients with Menière's disease (44 affected ears) and a group of 50 young normal hearing subjects. No significant differences in perilymphatic pressure measurements were found between the groups. Although measurement parameters showed large inter-individual variation in a subgroup of 25 patients, the intra-individual correlation in the subgroup was good. In patients with Meniere's disease no relationship was found between perilymphatic pressure, hearing thresholds, blood pressure, gender or age. There was no difference between unilaterally and bilaterally affected patients.

Transient hearing decrease following loss of cerebrospinal fluid (CSF) has been reported in patients undergoing lumbar puncture, spinal anesthesia, myelography, and/or different neurosurgical interventions. The authors present the first well-documented case of a patient with persistent bilateral low-frequency sensorineural hearing loss after shunt placement for hydrocephalus and discuss the possible pathophysiological mechanisms including the role of the cochlear aqueduct. These findings challenge the opinion that hearing decreases after loss of CSF are always transient. The authors provide a suggestion for treatment.

Electrocochleographic recordings after changes of middle-ear and intracranial pressure were studied in a group of otologically normal subjects and in patients with suspected Ménière's disease. Electrocochleography performed under these conditions was called stress electrocochleography. It was useful to distinguish among Ménière's disease, benign positional vertigo, and a round-window fistula. Changes of middle-ear pressure, whether positive or negative, always resulted in a rise of the SP/AP ratio. Raised intracranial pressure after Trendelenburg positioning showed fluctuations of the SP/AP ratio in both normal subjects and symptomatic patients. However, in normal subjects, a congruent pattern of these fluctuations was apparent, whereas symptomatic patients exhibited a discordant pattern. The discordant pattern, typical for Ménière's disease, showed an increase of the SP voltage, whereas the AP voltage decreased. In benign positional vertigo, the SP voltage decreased, and the AP voltage increased, once during Trendelenburg positioning and again at the end of the test when starting position was resumed. During raised intracranial pressure after the Queckenstedt maneuver, round-window fistulas showed an increase of the SP voltage, whereas the AP voltage decreased considerably. At our clinic, stress electrocochleography has become an important neurootological test in the differential diagnosis of Ménière's disease.

The hydrostatic pressure of the inner ear depends on the cerebrospinal fluid pressure through the cochlear aqueduct. The time-course of inner ear pressure change following rapid change in cerebrospinal fluid pressure is related to the aqueduct patency. In this study the patency of the cochlear aqueduct in 27 patients with Menière's disease (28 affected ears, 16 non-affected ears) and in 12 normal hearing subjects (18 control ears) was assessed non-invasively by means of the MMS-10 Tympanic Displacement Analyser. Following a rapid change in body position, changes in intracranial cerebrospinal fluid pressure were found to influence perilymphatic pressure within 1 min. No significant differences were found among affected ears, non-affected ears and control ears.

Background: The cochlear aqueduct is a route for direct pressure transfer between intracranial and intracochlear fluids. In patients with Menière's disease, intracochlear pressure is presumably disturbed. The "Tympanic Membrane Displacement Analyser (TDA)" is a new system which provides a useful noninvasive method of detecting intracranial and intracochlear pressure changes., Patients: In this study TDA measurements in combination with a glycerol test were performed in nine patients with Menière's disease and in seven normal persons., Results: Before ingestion of glycerol, no significant difference in pressure was found between the two groups. After ingestion of glycerol a temporary decrease in intracochlear pressure was detected in both groups without any significant difference between the two groups., Conclusion: These results show that the combination of glycerol testing and TDA measurements does not seem to be helpful for the differential diagnosis of Menière's disease.

Sudden hearing loss and new-onset vestibular disorders can be caused by perilymphatic fistulas (PLFs). In children, the existence of a severe or profound sensorineural hearing loss (SNHL) has been associated with a perilymphatic fistula when a sudden hearing loss or vestibular disturbance occurs. Likewise, at the other end of the age spectrum, several large series of PLFs in adulthood have been presented. This report focuses on a neglected age group, those in their teens and young adulthood. Twenty-three patients between the ages of 17 and 26 were studied who had a preexisting SNHL and had developed an additional hearing loss, a new vestibular disturbance, or both. An age-matched cohort of 21 patients with normal hearing was examined in relation to their medical history, diagnostic tests, and surgical outcome of a perilymphatic fistula repair. The findings of this report suggest that persons who have a preexisting SNHL are more likely to develop a perilymphatic fistula eventually than are persons with normal hearing.

Clear fluid found in the dependent portions of the middle ear (round and oval windows) is generally assumed to be perilymph (PL). However, all clear fluid observed at middle ear exploration is not necessarily PL. PL should be distinguished from local injection. An accumulation of the local injection could be confused with perilymph fistula (PLF) diagnosis. There is no standard way of distinguishing perilymph from local injection, as both are clear, watery fluids. Fluorescein, tagged with a mixture of xylocaine and epinephrine (FLOTAX) was used as the local injection in 10 patients undergoing middle ear exploration for possible PLF.FLOTAX was injected into the vascular strip and ear canal skin in routine fashion. Transtympanic endoscopy and special Zeiss custom fluorescein filters were used to document any accumulation of fluid in the dependent portions of the middle ear and confirm whether any fluorescein (from the FLOTAX) was present. The middle ear was checked both before (endoscopically) and after raising the tympanomeatal flap. After the "local" injection, FLOTAX was observed to accumulate in dependent portions of the middle ear before raising the tympanomeatal flap in six of 10 ears. In the other four ears, FLOTAX slowly seeped into the middle ear cleft after the tympanomeatal flap was elevated and manipulated. Fluorescein can be used as an inexpensive, indirect intraoperative marker or "reverse test" for possible PLF. By eliminating a likely and common offender (local injection), any accumulation or reaccumulation of clear fluid that is not fluorescein tagged may more confidently be identified as possibly perilymph. The use of FLOTAX helps eliminate the confusion between the local injection and potential PLF. It does not in any way eliminate the possibility of other transudates from incisions, allergic reactions, or other manipulation of the tympanomeatal flap or middle ear mucosa.

Sealing the opening of the oval window during stapes surgery is essential; it prevents postoperative complications, such as perilymph fistula and sensorineural hearing loss. In this small series of 269 cases with otosclerosis, tympanosclerosis, and congenital ossicular abnormality, vein grafting was used to seal the opening of the footplate. Hearing improvement after surgery was acceptable, and none had total hearing loss or perilymphatic fistula. World literature from the last half of this century on grafting the oval window is reviewed. Absorbable gelatin sponge (Gelfoam) seems to be causing more complications, so its use is highly discouraged. Temporalis fascia, fat, and perivenous loose areolar tissue have been used by different authors at different times in footplate surgery. The opening created in the oval window during stapes surgery must not be left uncovered.

Tinnitus is characterized by the continuous or intermittent auditory perception of various sounds (buzzing, whistling, etc.) in the absence of any external stimulus. Perilymphatic hyperpressure is one of the numerous mechanisms which could hypothetically be involved in tinnitus generation. In the present experiment, perilymphatic pressure was measured indirectly using the tympanic membrane displacement technique. Twenty-five tinnitus patients were investigated at 10, 15 and 20 dB above the acoustic reflex threshold with ipsilateral stimulation. The variables Vi (inward tympanic displacement), Vm (mean tympanic displacement) and their variations according to stimulus level were compared between tinnitus sufferers and age-matched or hearing-matched controls. Tympanic displacement was measured in sitting and supine positions so as to evaluate cochlear aqueduct patency. No systemic changes in response occurred in tinnitus patients, except at a high stimulation level, perhaps due to hearing impairment.

Intracranial pressure is transmitted to the perilymph of the cochlea via the cochlear aquaeduct and via Reissner's membrane to the endolymph. The "Tympanic Membrane Displacement Analyser (TDA)" is a new device that may be a useful non-invasive method to show intracranial and intracochlear pressure changes indirectly measured by tympanic membrane displacement during stapedial reflex contraction. The TDA was utilised in 20 normal persons and in 29 patients with unilateral diseases of the inner ear. No significant differences in the tympanic membrane displacement were found between patients with sensorineural hearing loss, patients with Ménière's disease, and normal persons.

It was the scope of two previous papers to outline the basics and possible neurotological applications of the tympanic membrane displacement technique (TMD). The present paper is aimed at briefly reviewing five distinct cases where a sudden sensorineural hearing loss with/without tinnitus could be monitored by the TMD technique. These features include a sudden hearing loss upon lumbar puncture, the audiological manifestation of an internal hydrocephalus, stapes gusher and the round window rupture. All symptoms are based on a change in intracranial and intracochlear pressure which in turn leads to the manifestation of the previously unknown sensorineural hearing loss and/or tinnitus.

The purpose of the present study was to measure changes in cerebrospinal fluid pressure (CSF-P) during actions of daily life. A spinal tap was performed on 23 inpatients. During the procedure, the patients were requested to perform the following four actions: nose blowing with one side closed, nose blowing with both sides closed, breath holding, and sniffing. The CSF-P was recorded before and during these actions. Of these, nose blowing with both sides closed resulted in the greatest elevation of pressure. Three patients with perilymph fistula showed larger changes than the other 20 patients. Conversely, sniffing lowered the CSF-P in all cases. The present study suggests that daily physical actions cause significant elevations of CSF-P. Such changes may be responsible for the development of perilymph fistula.

The intracochlear pressure cannot yet be evaluated in patients with certain audiological neuro-otological diseases. However, it seems to be of importance in the diagnosis and pathogenesis of Ménière's disease and related disorders. The present paper is aimed at introducing a setup to indirectly assess intracochlear and intracranial pressure changes and the design and philosophy of this technique. It is possible to describe a normal range of the measured values in healthy controls although large interindividual variations occur. In addition, the positional changes of the registered parameters enable assessment of the patency of the cochlear aquaeduct. This seems to be important in some diseases, such as stapes gusher.

Nine cats with the cochlear aqueduct surgically blocked were anaesthetised, put in a pressure chamber, and stepwise exposed to hypobaric pressure, each of the two steps lasting 5 min. The chamber pressure was reduced to -5 and -7 kPa. Concluding the experiment the cats were observed for 5 min after restoration of atmospheric pressure. The perilymph, tympanic cavity, cerebrospinal fluid, central venous, arterial and surrounding chamber pressures were continuously recorded. Reduced chamber pressure caused relative overpressure within the tympanic cavity, thereby inducing pressure gradients between the chamber, the tympanic cavity, the labyrinth and the cerebrospinal fluid and vascular pressures respectively. Our results demonstrate that hypobaric effects on the labyrinth are mediated via pressure changes in the tympanic cavity and not by systemic, vascular or cerebrospinal fluid influence. Substantial perilymph overpressure lasted throughout the hypobaric conditions. The magnitude and the duration of this overpressure were influenced by the patency of the Eustachian tube whereas the rate of the pressure change in the chamber was of little importance. As atmospheric pressure was restored in the chamber the overpressure in the labyrinth was reversed to underpressure--relative to pre-experimental conditions.

Perilymphatic fistula can be difficult to diagnose differentially prior to exploratory surgery. In this study, we investigated a new test technique in four case studies of subjects with perilymphatic fistula and compared our findings to results obtained in 20 normally hearing subjects with no history of vertigo and 10 subjects with Meniere's disease. Recordings from an eardrum electrode were obtained with the subject in an upright position, after the subject had been lying in a horizontal position for 30 minutes with the test ear up and after 15 minutes with the test ear down. Stimuli consisted of high level clicks and tonebursts. Neither the summating potential (SP) and action potential (AP) amplitudes nor the SP/AP amplitude ratio were significantly affected by postural change in either the normal or Meniere's disease group. The perilymphatic fistula subjects, in general, showed greater changes in the SP/AP, particularly for the 6000 Hz tonebursts, than did the other two groups. More data will be needed to determine if these findings are consistent in a large population of perilymphatic fistula patients.

Controversy exists surrounding the diagnosis of spontaneous perilymphatic fistula. In an effort to help resolve this controversy the author conducted a review of the literature as well as a review of 212 of his patients who underwent surgical exploration for suspected perilymphatic fistula. Interpretation of the literature reviewed was hampered by the lack of a uniformly accepted definition for the word spontaneous. Dorland's Medical Dictionary defines spontaneous as that which occurs without external influence. Webster's Dictionary, on the other hand, provides a much more confining definition of the word by stating that a spontaneous event is one that occurs or is produced by its own energy. Only 58 percent of the author's 212 patients had an antecedent history of an external event that may have precipitated the suspected perilymphatic fistula (trauma, flying, diving) while almost 41 percent recalled an antecedent event of internal origin (lifting, straining, sneezing, nose blowing). If one were to support the definition of spontaneous provided by Dorland's Medical Dictionary, then the 41 percent of patients who had no antecedent history of external event would have to be considered as having spontaneous perilymphatic fistula. If, on the other hand, one were to endorse the definition of spontaneous provided by Webster's then less than 2 percent of the author's patients would have to be considered as having spontaneous perilymphatic fistula.

Obliteration of the endolymphatic sac reliably results in endolymphatic hydrops in some animal species. While this procedure is frequently utilized in the study of experimental Meniere's disease, additional information regarding inner ear fluid hydrodynamics can be obtained by obstructing the cochlear aqueduct to eliminate the influence of the cerebrospinal fluid on the perilymphatic compartment of the inner ear. This report describes a modified extradural occipital approach for surgical obliteration of the endolymphatic sac and obstruction of the cochlear aqueduct in the guinea pig. The extradural approach allows direct visualization of the cochlear aqueduct without manipulation or retraction of the dura, sigmoid sinus, or cerebellum. For experimental studies, which require obliteration of both the endolymphatic sac and cochlear aqueduct, this approach provides improved reliability with reduced morbidity and mortality.

This study investigated the prevalence of perilymphatic hypertension (raised perilymphatic pressure) in a population of subjects with tinnitus. A review of the literature showed how changes in perilymphatic pressure could affect tympanic membrane displacement measurements. This review also revealed that perilymphatic hypertension was more likely to occur in young females (less than 45 years) than in other subjects. An experiment was designed to test 32 subjects, who were divided into four groups according to their age and sex. These subjects underwent several routine audiological tests and were then tested with the tympanic membrane measurement system to determine the perilymphatic pressure of both ears. Statistical analysis of the experimental results showed that the young females had raised perilymphatic pressure. This was significantly higher than the perilymphatic pressure of the other test groups and of that of a normal population. The young females also exhibited other symptoms indicative of raised perilymphatic pressure. The raised pressure was thought to be due to an increase in fluid pressure which is more likely to occur in females due to variations in the levels of circulating hormones with menstrual irregularities, pregnancy and the menopause.

The present study summarizes the experimental findings obtained on the pressure in the inner ear fluids and on the effects of pressure changes on cochlear function in the guinea pig. Two types of pressures have to be distinguished in the inner ear fluid compartments: (i) hydrostatic fluid pressure and (ii) superimposed hydrodynamic high frequency (> 100 Hz) sound pressure oscillations. Hydrostatic pressure in the inner ear fluids in guinea pigs is in the order of 200 Pa (2 cm H2O) and shows slow (< 5 Hz) respiratory and pulsatory oscillations as well as considerable physiological variations in the range of -100 to +700 Pa. In normal ears, hydrostatic pressure in the perilymph equals pressure in the endolymph, and pressure changes applied to one compartment are immediately transmitted to the other one. A high compliance of Reissner's membrane seems to be the cause of this endolymphatic-perilymphatic pressure equalization. In experimental endolymphatic hydrops, a unique animal model for Meniere's disease, endolymphatic pressure is higher (100 Pa and above) than perilymphatic pressure. These pressure gradients occur only in late stages of hydrops, probably when Reissner's membrane has lost its high compliance after long standing distension. Positive endolymphatic-perilymphatic pressure gradients are secondary to and not the primary cause of hydrops formation. Changes of hydrostatic pressure do not affect auditory function as long as they stay in the physiological range. This includes the sudden loss of positive inner ear pressure that occurs in perilymph fistulas. The rationale for surgical repair of perilymph fistulas in patients in order to restore the hearing function thus becomes questionable. Other aspects of surgical repair, however, as e.g. prevention of labyrinthitis due to permanently open fistula, could not be investigated in this model, because in guinea pigs even large fistulas heal spontaneously within a few days. In experimental endolymphatic hydrops, deterioration of auditory thresholds was partially correlated to the presence of positive endolymphatic-perilymphatic pressure gradients. A change in pressure, however, occurred later than the first deterioration in auditory function. Therefore positive endo-perilymphatic pressure gradients may contribute to, but are not the only cause of hearing impairment.

The aim of the present study was to evaluate the effect of experimental perilymphatic fistula on cochlear electrophysiological responses. Six albino guinea pigs, in which recording electrodes were implanted in order to record the electrocochleogram, were used. Experimental protocol investigated cochlear responses before the induction of the fistula in the round window membrane perforation and then two month later. Compound action potential thresholds increased immediately after perforation of the round window membrane. The thresholds rapidly recovered. This phenomenon was accompanied by clear-Out reduction in amplitude upon suprathreshold stimulation. This latter observation associated with a decrease in the amplitude of the threshold seems to be a specific audiologic sign of the fistula. The clinical implication are discussed.

Alterations of cochlear function secondary to perforation of the round window membrane in guinea pigs were expected to reveal sensitive and/or specific audiometric parameters in perilymph fistulas. A perforation of the round window membrane either did not affect acoustic compound action potential thresholds, or induced a delayed, possibly conductive, inner ear hearing loss. Also, evoked suprathreshold responses deteriorated progressively and independently of the increase of compound action potential thresholds. A sudden (conductive) hearing loss and a poor response to suprathreshold stimulation might indicate inner ear damage secondary to a perilymphatic fistula.

The effects of sudden occlusion of the vein of the cochlear aqueduct (VCAQ) on the cochlear blood flow, endocochlear potential (EP), endolymphatic and perilymphatic fluid pressures (PE and PP) were studied in the guinea pig. Cochlear blood flow showed a sudden decrease, and EP began to drop within 90 s, ranging from 50 to 70 mV in 5 of 11 animals studied, recovering to normal levels when the animals were placed on a continuous inhalation of carbogen. The PE and PP increased simultaneously (max. PE = 3.4 +/- 1.4 mm Hg; max. PP = 2.5 +/- 1.0 mm Hg) and returned to their initial values after 5 min. The EP was sustained within the normal range, even when there was an apparent decrease in cochlear blood flow (61.4 +/- 8.4%). We believe that variations in EP following VCAQ occlusion were due to anatomical differences in collateral venous communications among the animals studied. Carbogen inhalation produced uniform recovery patterns, indicating that individual collateral vessel responses were eliminated.

In 41 guinea pigs an experiment was conducted to determine the effect of kanamycin on ears with or without blockage of the cochlear aqueduct. In 24 animals the cochlear aqueduct was blocked on one side, and after 1 to 21 days, kanamycin (300 mg/kg) was given daily and subcutaneously until the pinna reflex began to decrease. The remaining animals were used for controls: exposure of and trauma to the aperture of the cochlear aqueduct and kanamycin administration (8), blockage of the cochlear aqueduct only (3 plus 17 previous cases), and kanamycin administration to normal animals (6). The survival time of all these animals was four months. The results showed that ears with blockage of the cochlear aqueduct and kanamycin administration consistently demonstrated a more severe and extensive atrophy of the cochlear sensory cells. The lesions occurred primarily at the basal end and spread toward the apical turn, although the lesions in some specimens jumped from the basal to apical turn. The outer hair cells were more extensively affected than the inner hair cells. Proteinaceous precipitates were often found to be slightly greater in the perilymph of cochleae with blocked cochlear aqueducts. From these observations, it is concluded that the decrease in patency of the cochlear aqueduct will impair perilymph metabolism, causing the cochlear sensory cells at the basal turn to become more vulnerable to noxious substances.

The cause of perilymph fistula, a subgroup of sudden deafness, has not been clearly understood. To study its etiology quantitatively, the inner ear pressure monitoring system with a computer controlled pressurizing device and three types of low-pressure monitoring sensors was constructed and utilized in ex vivo experiments using white guinea pigs. Hypothesizing that cerebrospinal pressure increases cause rupture of the round window membrane, direct and indirect pressurization to cerebrospinal region and simultaneous measurement of inner ear and cerebrospinal pressures were carried out. Ruptures of the round window membranes were seen in the experiments with direct saline infusion into the cochlea when the increment of inner ear pressure exceeded 500 mmH2O. There was no sign of rupture when squeezing abdomen was employed as an indirect pressurization, although cerebrospinal pressure increased.

There is convincing evidence that the cochlear aqueduct is normally patent in humans and is of relatively constant size. It probably plays an important role in the balance between the perilymphatic, endolymphatic, and cerebrospinal fluid pressures. The flow rate of liquids through tubes is a linear function of pressure, viscosity, and length of the tube but is a fourth degree power function of the radius of the lumen. For this reason, the radius is the most critical factor determining the flow rate. Small variations in size of the cochlear aqueduct can cause very large variations in flow rate through it.

Over 250 reports concerning or related to Meniere's disease, published in English from 1978 through 1982, are summarized. Reports have been classified into the categories of incidence of occurrence, analysis and reporting results, pathophysiology, etiologic theories, diagnostic methods, medical management, and surgical procedures. Major emphases in reporting from 1978 though 1982 have been in the areas of pathophysiologic studies, expansion of diagnostic procedures, and the use of sac decompression and neurectomy procedures. This literature review reveals the continuing disagreement regarding the pathophysiology of Meniere's disease and the resultant continued controversies in its management.

Dizziness in childhood may be the result of significant vestibular or central nervous system pathology. It is the responsibility of otolaryngologists and neurologists to provide appropriate diagnosis and treatment of these disorders.