THE PATHOLOGY OF SUDDEN DEAFNESS

Bidirectional Association Between Sudden Sensorineural Hearing Loss and Glaucoma: A Cohort Study

OBJECTIVES

To investigate the bidirectional association between sudden sensorineural hearing loss (SSNHL) and open-angle glaucoma (OAG) over a 12-year follow-up period using nationwide, population-based data.

METHODS

The study was conducted using the National Health Information Database of the National Health Insurance Service (NHIS-NHID), which covered 3.5 million individuals from 2008 to 2019. In Study 1, we evaluated the effect of OAG on SSNHL, and in Study 2, we evaluated the effect of SSNHL on OAG. Participants of the control group were enrolled through "greedy nearest-neighbor" 1:1 propensity score matching.

RESULTS

In Study 1, 26,777 people were included in each group. The hazard ratio (HR) for SSNHL of the OAG group was 1.27 (95% confidence interval [CI], 1.15-1.39). In subgroup analysis, there was significant HR value regarding (old age: 1.17, hyperlipidemia: 1.19). In Study 2, 15,433 people were included in each group. The HR for OAG of the SSNHL group was 1.18 (95% CI, 1.07-1.30). In subgroup analysis, the HRs were significant for old age (2.31), hypertension (1.17), diabetes (1.39), and hyperlipidemia (1.26).

CONCLUSION

Over the 12-year follow-up, we found a bidirectional association between SSNHL and OAG, suggesting a shared pathogenesis.

LEVEL OF EVIDENCE

N/A. Laryngoscope, 133:3169-3177, 2023.

Influence of Metabolic Syndrome on the Recovery from Idiopathic Sudden Sensorineural Hearing Loss

Introduction  Idiopathic sudden sensorineural hearing loss (ISSHL) is a disabling otologic urgency whose ethiopathogenesis is still controversial. Only in recent years metabolic syndrome (MetS) has been implicated as a possible aggravating factor in the prognosis of recovery from ISSHL.

Objective  To assess whether the preexistence of MetS interferes on hearing recovery levels.

Methods  Retrospective cohort study composed of adult (> 18 years old) ISSHL patients admitted for treatment between January 2015 and December 2019. To diagnose ISSHL, we used pure-tone audiometry, and identified MetS patients based on the criteria of the United States National Cholesterol Education Program Adult Treatment Panel III (NCEP ATP III). The treatment protocol comprised hospitalization for five days for the intravenous administration of dexamethasone, audiometric surveillance, imaging and blood analyses, and, based on recovery, the planning of rescue treatments (intratympanic administration of dexamethasone and/or hyperbaric oxygen). The Siegel criteria were used to evaluate the hearing outcomes.

Results  The final sample was composed of 81 patients, 48 without MetS (nMetS) and 33 with MetS. Regarding the Siegel recovery category, the nMetS group had significantly better results ( p  = 0.001), with 44% of complete recoveries against 6% in the MetS, and 58% of the MetS patients had the worst outcome, contrasting with 27% in the nMetS group. The nMetS group had an overall better evolution in terms of hearing recovery and had a significant improvement in the median hearing gain (20.6 dB versus 8.8 dB; p  = 0.008). Additionally, the multivariate analysis revealed that the presence of MetS is a significant risk factor for a worse outcome (odds ratio [OR] = 0.30; 95% confidence interval [95%CI] = 0.10–0.85).

Conclusion  Regardless of age, gender, the initial audiometry threshold, and autoimmunity, MetS is a clear risk factor for a worse outcome regarding the recovery of hearing after ISSHL.

Idiopathic Sudden Sensorineural Hearing Loss: Speech Intelligibility Deficits Following Threshold Recovery

OBJECTIVES

This retrospective study tests the hypothesis that patients who have recovered from idiopathic sudden sensorineural hearing loss (SSNHL) show deficits in word recognition tasks that cannot be entirely explained by a loss in audibility.

DESIGN

We reviewed the audiologic profile of 166 patients presenting with a unilateral SSNHL. Hearing loss severity, degree of threshold recovery, residual hearing loss, and word recognition performance were considered as outcome variables. Age, route of treatment, delay between SSNHL onset and treatment, and audiogram configuration were considered as predictor variables.

RESULTS

Severity, residual hearing loss, and recovery were highly variable across patients. While age and onset-treatment delay could not account for the severity, residual hearing loss and recovery in thresholds, configuration of the SSNHL and overall inner ear status as measured by thresholds on the contralateral ear were predictive of threshold recovery. Speech recognition performance was significantly poorer than predicted by the speech intelligibility curve derived from the patient's audiogram.

CONCLUSIONS

SSNHL is associated with (1) changes in thresholds that are consistent with ischemia and (2) speech intelligibility deficits that cannot be entirely explained by a change in hearing sensitivity.

Intratympanic Triamcinolone Acetonide as a Salvage Treatment for Idiopathic Sudden Sensorineural Hearing Loss

INTRODUCTION

Intratympanic steroid (ITS) injections represent an increasingly used salvage treatment option for patients with idiopathic sudden sensorineural hearing loss -(ISSHL) after systemic treatment. The most effective corticosteroid for this treatment modality still remains unclear. Triamcinolone acetonide has been used for ITS treatment in various clinical settings. However, there are limited clinical data of its usage in the therapeutic management of ISSHL. The aim of this study was to determine the efficacy of intratympanic triamcinolone acetonide injections as a salvage treatment for ISSHL.

METHODS

We conducted a retrospective chart review on patients affected by ISSHL with insufficient hearing recovery after primary systemic corticosteroid therapy and who were treated with intratympanic triamcinolone acetonide as a salvage therapy between January 2014 and August 2019. The patients were divided into groups according to their degree of hearing recovery, and we evaluated potential predictors of hearing recovery. Audiometric results were then compared to historic studies using dexamethasone or methylprednisolone.

RESULTS

One-hundred and fifty-two patients received up to 3 intratympanic injections with triamcinolone acetonide at 1-week intervals. The mean hearing improvement due to ITS salvage treatment was 15.9 ± 18.9 dB. Complete hearing recovery was noted in 15 patients (9.9%), while 73 patients (48%) obtained partial recovery, and 64 patients (42.1%) had no recovery. Primary systemic treatment delay, hearing improvement by primary systemic treatment, and severity of initial hearing loss were identified as significant predictors of hearing improvement. The first of the 3 injections resulted in the greatest hearing improvement.

CONCLUSION

The use of triamcinolone acetonide in ITS salvage treatment resulted in similar hearing improvements as the use of the commonly used corticosteroids, namely, dexamethasone and methylprednisolone. Longer treatment delays, lower hearing improvement by primary systemic treatment, and higher initial hearing loss are associated with poorer prognoses of hearing recovery.

Sudden sensorineural hearing loss: Is there a connection with inner ear electrolytic disorders? A literature review

Electrolytic disorders of the inner ear represent a model that could be implicated in partially explaining the pathogenesis of sudden sensorineural hearing loss (SSNHL). Different types of electrolytes and different inner-ear loci are involved in cochlear homeostasis physiologically, to ensure the maintenance of an ion-balanced cochlear environment allowing a normal hair cell function. It has been hypothesized that a sudden loss of endocochlear potential, due to a rapid disruption of the inner ear fluid osmolality, could be responsible for a deterioration of the hearing function caused by damaged hair cells. The aim of this paper was to review the current literature and identify sources which might validate/fortify the hypothesis that inner ear electrolytic disorders have a role in the etiopathogenesis of SSNHL. The data in the literature underline the importance of ionic homeostasis in the inner ear, but they do not support a direct link between SSNHL and electrolyte disorders/imbalances. There is marginal evidence from otoacoustic emissions research that an indirect link might be present.

A Cell Culture Model of Latent and Lytic Herpes Simplex Virus Type 1 Infection in Spiral Ganglion

PURPOSE OF THE STUDY

Reactivation of latent herpes simplex virus type 1 (HSV-1) in spiral ganglion neurons (SGNs) is supposed to be one of the causes of idiopathic sudden sensorineural hearing loss. This study aims to establish a cell culture model of latent and lytic HSV-1 infection in spiral ganglia.

PROCEDURES

In the presence of acyclovir, primary cultures of SGNs were latently infected with HSV-1 expressing green fluorescent protein. Four days later, these cells were treated with trichostatin A (TSA), a known chemical reactivator of HSV-1. TCID50 was used to measure the titers of virus in cultures on Vero cells. RNA from cultures was detected for the presence of transcripts of ICP27 and latency-associated transcript (LAT) using reverse transcription polymerase chain reaction.

RESULTS

There is no detectable infectious HSV-1 in latently infected cultures, whereas they could be observed in both lytically infected and latently infected/TSA-treated cultures. LAT was the only detectable transcript during latent infection, whereas lytic ICP27 transcript was detected in lytically infected and latently infected/TSA-treated cultures.

CONCLUSION

Cultured SGNs can be both latently and lytically infected with HSV-1. Furthermore, latently infected SGNs can be reactivated using TSA, yielding infectious virus.

Virus-induced expression of retinoic acid inducible gene-I and melanoma differentiation-associated gene 5 in the cochlear sensory epithelium

The inner ear has been regarded as an immunoprivileged site because of isolation by the blood-labyrinthine barrier. Several reports have indicated the existence of immune cells in the inner ear, but there are no reports showing immunocompetence of the cochlear tissue. In this report, we examined the potential involvement of retinoic acid inducible gene-I (RIG-I) and melanoma differentiation-associated gene 5 (MDA5), which are critical for initiating antiviral innate immune responses. We found that RIG-I and MDA5 are expressed in the mouse cochlear sensory epithelium, including Hensen's and Claudius' cells. Ex vivo viral infection using Theiler's murine encephalomyelitis virus revealed that the virus replicates in these cells and that protein levels of RIG-I and MDA5 are up-regulated. Furthermore, the critical antiviral transcription factor, interferon (IFN) regulatory factor-3, is activated in the infected cells as judged by its nuclear translocation and the accumulation of type I IFN transcripts. These results strongly suggest that RIG-I and MDA5 participate in innate antiviral responses in cochlear tissue.

Sudden sensorineural hearing loss: a review of diagnosis, treatment, and prognosis

Sudden sensorineural hearing loss (SSNHL) is commonly encountered in audiologic and otolaryngologic practice. SSNHL is most commonly defined as sensorineural hearing loss of 30 dB or greater over at least three contiguous audiometric frequencies occurring within a 72-hr period. Although the differential for SSNHL is vast, for the majority of patients an etiologic factor is not identified. Treatment for SSNHL of known etiology is directed toward that agent, with poor hearing outcomes characteristic for discoverable etiologies that cause inner ear hair cell loss. Steroid therapy is the current mainstay of treatment of idiopathic SSNHL in the United States. The prognosis for hearing recovery for idiopathic SSNHL is dependent on a number of factors including the severity of hearing loss, age, presence of vertigo, and shape of the audiogram.

Chikungunya virus induced sudden sensorineural hearing loss

The aim of this study is to demonstrate the association of Chikungunya virus and sudden sensorineural hearing loss. In the case report described we had a case which developed sudden unilateral sensorineural hearing loss following chikungunya fever. A 15-year-old female presented to us with the complains of unilateral sudden onset of hearing loss following an episode of fever, arthralgia and rashes 1 month ago. At the time of these symptoms there were many cases of chikungunya fever in the city, three being in her locality. Clinically Chikungunya fever was suspected and a positive serological test further confirmed our diagnosis. The hearing loss could thus be attributed to Chikungunya virus. Viruses have always been implicated in causing sudden sensorineural hearing loss but Chikungunya virus as a cause has not been documented earlier making this case report a unique one.

Sudden deafness: is it viral?

A number of theories have been proposed to explain the etiopathogenesis of idiopathic sudden sensorineural hearing loss (ISSHL), including viral infection, vascular occlusion, breaks of labyrinthine membranes, immune-mediated mechanisms and abnormal cellular stress responses within the cochlea. In the present paper, we provide a critical review of the viral hypothesis of ISSHL. The evidence reviewed includes published reports of epidemiological and serological studies, clinical observations and results of antiviral therapy, morphological and histopathological studies, as well as results of animal experiments. The published evidence does not satisfy the majority of the Henle-Koch postulates for viral causation of an infectious disease. Possible explanations as to why these postulates remain unfulfilled are reviewed, and future studies that may provide more insight are described. We also discuss other mechanisms that have been postulated to explain ISSHL. Our review indicates that vascular occlusion, labyrinthine membrane breaks and immune-mediated mechanisms are unlikely to be common causes of ISSHL. Finally, we review our recently proposed theory that abnormal cellular stress responses within the cochlea may be responsible for ISSHL.

Pathology and Pathophysiology of Idiopathic Sudden Sensorineural Hearing Loss

BACKGROUND

The cause and pathogenesis of idiopathic sudden sensorineural hearing loss remain unknown. Proposed theories include vascular occlusion, membrane breaks, and viral cochleitis.

AIMS

To describe the temporal bone histopathology in 17 ears (aged 45-94 yr) with idiopathic sudden sensorineural hearing loss in our temporal bone collection and to discuss the implications of the histopathologic findings with respect to the pathophysiology of idiopathic sudden sensorineural hearing loss.

METHODS

Standard light microscopy using hematoxylin and eosin-stained sections was used to assess the otologic abnormalities.

RESULTS

Hearing had recovered in two ears and no histologic correlates were found for the hearing loss in both ears. In the remaining 15 ears, the predominant abnormalities were as follows: 1) loss of hair cells and supporting cells of the organ of Corti (with or without atrophy of the tectorial membrane, stria vascularis, spiral limbus, and cochlear neurons) (13 ears); 2) loss of the tectorial membrane, supporting cells, and stria vascularis (1 ear); and 3) loss of cochlear neurons only (1 ear). Evidence of a possible vascular cause for the idiopathic sudden sensorineural hearing loss was observed in only one ear. No membrane breaks were observed in any ear. Only 1 of the 17 temporal bones was acquired acutely during idiopathic sudden sensorineural hearing loss, and this ear did not demonstrate any leukocytic invasion, hypervascularity, or hemorrhage within the labyrinth, as might be expected with a viral cochleitis.

DISCUSSION

The temporal bone findings do not support the concept of membrane breaks, perilymphatic fistulae, or vascular occlusion as common causes for idiopathic sudden sensorineural hearing loss. The finding in our one case acquired acutely during idiopathic sudden sensorineural hearing loss as well as other clinical and experimental observations do not strongly support the theory of viral cochleitis.

CONCLUSION

We put forth the hypothesis that idiopathic sudden sensorineural hearing loss may be the result of pathologic activation of cellular stress pathways involving nuclear factor-kappaB within the cochlea.

Alpha-Interferon for the treatment of idiopathic sudden sensorineural hearing loss

We have employed alpha-interferon (IFN-alpha), an anti-viral agent, in the treatment of severe idiopathic sudden sensorineural hearing loss (ISSHL). Forty-two patients were studied and had an average hearing ability of > or = 70 dB before treatment. We also examined 2'-5' oligoadenylate synthetase (2,5A-S) activity, one of the parameters indicating anti-viral activity of IFN, to investigate the relationship between the suppression of viral proliferation and prognosis and explain the pathogenesis of ISSHL. Complete recovery was found in 27 patients (64.3%) after IFN therapy. Increased 2,5A-S activity was observed on the 3rd day of IFN therapy in 24 of the 27 patients who completely recovered. No severe adverse events were reported after IFN therapy. Findings suggest that IFN therapy may be effective and safe in the treatment of ISSHL and calls for further investigation.

Multiple sclerosis as the cause of sudden 'pontine' deafness

Sudden deafness is rarely ascribed to multiple sclerosis (MS). Sudden deafness and tinnitus were the initial symptoms of MS for the two patients described in this paper. A sensorineural hearing loss was present in one ear in both patients. Brainstem responses (BSRs) showed only the first three waves for the first patient, and only wave I for the second. Magnetic resonance imaging showed focuses of demyelination in the pons (case 1) and on the borderline between medulla and pons (case 2). The placement of plaques and the involvement of the BSR-generating acoustic afferent pathways are discussed. The hearing level measured by tonal audiometry recovered after 1 month in both patients and remained stable during 1 year. BSRs remained pathological after 1 month as well as after 1 year. Sudden hearing loss and tinnitus might be the initial symptoms of MS.

Vestibular pathology of totally deaf ears

The temporal bone vestibular pathologies of 23 totally deaf ears (16 patients) were studied. Abnormal findings in the saccule were seen more often than in the other vestibular sensory organs. Abnormal findings in the vestibular ganglion cells were found in 7 ears. There were fewer ears with main damage in the hair cells than with main damage in the nerves.

Investigations into the cause of vertigo in sudden sensorineural hearing loss

In this light microscopic study of the temporal bone, an attempt has been made to find a morphologic correlate of vertigo associated with idiopathic sudden sensori-neural hearing loss (ISSHL). Hair cell densities of the three cristae and both maculae, as well as vestibular ganglion cell (neuronal) count estimation, was done in nine ears that had documented histories of ISSHL. There were five ears with vertigo and four without. These quantitative data--i.e., hair cell densities and neuronal counts, of the vertiginous ears (group I) and nonvertiginous ears (group II)--was compared by histograms and statistically. Additionally, in each of the two groups, the data from three opposite normal hearing ears were taken as a control and used for comparison with the ISSHL ears. The differences between the vertiginous, nonvertiginous, and control ears were not significant at the 0.01 level, indicating that the vertigo was not caused by hair cell or neuronal degeneration. Gross morphologic alterations in the vestibular system, such as membrane ruptures, endolymphatic hydrops, etc., were also assessed, but no clear-cut pathology was identified in the vertiginous and nonvertiginous ears. The absence of a light microscopic morphologic correlate for vestibular disturbances associated with ISSHL suggests that the symptoms could result from ultrastructural changes in the hair cells and their synapses or from biochemical alterations in their environment.

Idiopathic sudden sensorineural hearing loss and postnatal viral labyrinthitis: a statistical comparison of temporal bone findings

Although the cause of idiopathic sudden sensorineural hearing loss remains uncertain, a viral origin has been suggested in many cases on the basis of anamnestic microbiologic and pathologic data. Twenty-two temporal bone specimens from 18 patients who during life suffered a sudden partial or complete sensorineural hearing loss were studied. On the basis of clinical data, these cases were assigned to one of three diagnostic categories, and the temporal bones were studied by light microscopy and serial section analysis. The implications of the histopathologic findings for the pathogenesis of idiopathic sudden sensorineural hearing loss are discussed.

Traumatic perilymphatic fistulae of the lateral semicircular canal

Fifteen patients with perilymphatic fistulae were evaluated. Of these patients, three had CSF leaks in addition to the perilymphatic fistulae. Eight patients had fistulae of one or both windows; two had fistulae confined to the lateral semicircular canal; and two had combined fistulae of both round window and lateral semicircular canals. All improved dramatically following surgical repair. In the following study, we have shown that perilymphatic fistulae can occur in the lateral semicircular canal, and we suggest exploration of this area when indicated.

Rapidly progressive sensorineural hearing loss (rapid deafness)

28 ears of 28 patients, aged 15 to 60 years, whose sensorineural hearing loss had developed over a period of a few hours to 3 days, were defined as having rapidly progressing sensorineural hearing loss (rapid deafness), in comparison with so-called sudden deafness with instantaneous onset. For other criteria, their hearing loss was idiopathic and the rate of hearing loss was confirmed by reliable means. The rate was greatest within the first 1-3 days. Of the 28 patients, 12 (43%) recovered completely, while another 12 improved markedly. The prognosis in rapid deafness was relatively good, but the recovery time was longer than in spontaneously healing sudden deafness. Sensorineural hearing loss in contralateral ears more often preceded rapid deafness (9 cases, 32%). No clear-cut difference could be found between rapid deafness and sudden deafness.

Investigations into the cause of canal paresis in Menière's disease

Since the literature has a paucity of documented lesions of the vestibular hair cells and neurons in Menière's disease, the cause of canal paresis remains unexplained. A clinicopathological correlation was sought and demonstrated between ampullary distortion of lateral canal and reduced caloric response. The findings in this investigation make a strong case for ampullary distortion disrupting the tenuous but vital cupulary attachment resulting in canal paresis. This concept is attractive because it explains an important clinical event in Menière's disease on the basis of the only consistent histopathological finding, namely, membrane distension.

Epidemiological considerations in sudden hearing loss: a study of 183 cases

We have studied certain epidemiological problems not often encountered in the literature, involving patients with sudden hearing loss. We performed a retrospective cross-sectional study on 183 patients at the University of Padova and found that: age at the onset of the hearing loss incurred is closely associated with the presence of concomitant diseases; partial or total recovery of hearing is strongly predicated by the variables of age at onset and the interval between onset of hearing loss and the beginning of treatment given. We have also used polar-coordinate diagrams to show that cases of sudden hearing loss tend to be cyclic and are more prevalent in the central months of each season.

The relationship of the herpesvirus family to sudden hearing loss: a prospective clinical study and literature review

The herpesvirus family is associated with sudden hearing loss syndrome and the evidence includes clinical findings (HV-Z), temporal bone studies (CMV and HV-Z), and serologic studies. The data presented demonstrate that herpes infections, in association with sudden viral hearing loss, occur as part of a multiple viral infection in 70% of instances. This feature is unique to the herpesvirus infections when compared to other neurotropic viral agents. The study also demonstrates that the variables of viral hearing loss, such as degree of hearing loss, percentage of recovery, or the incidence of vertigo are unaffected by the presence of herpesvirus infection. Mechanisms for inner ear injury may be influenced by temporary alterations in cellular immunity secondary to simultaneous viral infections as well as the native virulence of the infecting herpesvirus.

The pathology of idiopathic sudden sensorineural hearing loss

We examined the temporal bone pathologies in 12 ears with idiopathic sudden sensorineural hearing loss, and found that the lesions present in these specimens and in 10 others reported in the literature are similar to lesions occurring in known cases of viral cochleitis. These lesions are unlike those resulting from known vascular causes.

Sudden sensorineural hearing loss: operative complication in non-otologic surgery

Sudden sensorineural hearing loss is a well recognized phenomenon in otologic practice with both viral and vascular etiologies being supported. However, sudden hearing loss as a complication of non-otologic surgical procedure is a seldom reported and rare phenomenon. Five cases of unilateral sudden sensorineural hearing loss which are time related and probably causally related to non-otologic surgery are presented. Two cases underwent open heart surgery and support previous reports of hearing loss secondary to cardiopulmonary bypass procedures. Three noncardiac cases are also reviewed. None of these patients had prior otologic disease which would predispose to a sudden hearing loss, and no intraoperative or postoperative complication was specifically noted as a cause of the hearing loss. The literature is reviewed and attention is drawn to the problem. We wish to encourage further reports and to recommend early identification and treatment in those cases related to cardiopulmonary bypass.

Demyelinating disease as the assumed cause of hearing loss and vertigo. A case report with light- and electron-microscopic findings

A patient initially presenting typical symptoms of idiopathic sudden deafness later developed disabling episodic vertigo, which led to translabyrinthine eighth nerve transection. Morphological examination of the removed cochlear nerve specimen revealed a demyelinating process in the neuroglial portion of the nerve. The major part of the peripheral, neurolemmal portion of the cochlear nerve was normal. The inferior vestibular nerve was fibrotic. The major part of the superior vestibular nerve was normal. Some of its peripheral bundles showed increased endoneurial fibrosis. It is suggested that a demyelinating process was the cause of the patient's symptoms.

Electrocochleographic study of sudden deafness

By performing electrochleography (AP, SP and CM) on 34 patients with sudden deafness, it was thought that the pathophysiology of this disease could be deduced. The various waveform patterns of AP and SP responses obtained in cases of sudden deafness were classified into the following types: 1) AP high response; 2) decreased AP high response; 3) AP low response; 4) dominant -SP; 5) -SP or +SP; and 6) AP, SP no response. The cases showing the type of dominant -SP and AP high response had satisfactory prognoses. In these cases the sensory epithelium and the cochlear nerve seemed to indicate a reversible condition being affected by the temporary functional block. Furthermore, it seemed to indicate that the neural regions related to the source of AP(N1) response were impaired in cases in which CM were recorded at normal response threshold in spite of the absence of AP(N1) response. In the unsatisfactory prognosis cases with decreased AP high response, AP low response and AP, SP no response in which only the extremely low or depressed CM responses could be recorded, it seemed that the sensory epithelium and the cochlear nerve were affected permanently, although the degree of impairment varied.

Deafness in an old English sheepdog. A case report

The histopathological features of the inner ears in a case of deafness in an old English sheepdog reveal a cochleo-saccular (Scheibe) type of degeneration. However, also the hair cells in the vestibular part of the labyrinth were reduced in number though there appeared no clinical signs or symptoms of vestibular dysfunction. The present case is the so far only known old English sheepdog with a hearing loss reported in Sweden.

Sudden deafness with severe loss of cochlear neurons

We report our postmortem findings in the temporal bones of a patient who, at the age of 13, after having had a cold, experienced a sudden and profound hearing loss in her right ear. She died of nasopharyngeal carcinoma at 41. The patient's right temporal bone showed a complete loss of cochlear neurons, but the organ of Corti was well-preserved. These findings indicate a primary degeneration of the cochlear nerve. The authors speculated that the possible cause of this sudden deafness was severe neuronitis of the cochlear nerve.

Natural history of sudden sensorineural hearing loss

This is a prospective in-depth study of patients with sudden idiopathic sensorineural hearing loss. We found that 65% recover completely to functional hearing levels spontaneously and independent of any type of medical treatment. The majority do so within 14 days and many within the first few days. Prognosis can be predicted according to the slope of the initial audiogram (low-frequency losses do better than high-frequency losses), hearing at 8 kHz, erythrocyte sedimentation rates, in some select instances spatial disorientation symptoms, and speech discrimination scores. There was a very poor correlation between hearing and vestibular test abnormalities, except hypoactive calories. There were no correlations with age (excepting the very elderly), with antecedent respiratory infections, hypertension, diabetes, or other chronic diseases. We conclude that there is a fundamental difference in the behavior of apical and basal cochlea losses, that hearing recovery is always better at low than at high frequencies, that because of the high spontaneous recovery rates, tympanotomies seeking peri-lymph fistulas should be delayed ten days unless there is a progressive hearing loss, and that none of the current recommended treatments, especially histamine, have any effect on the outcome.

Sudden deafness: histopathologic correlation in temporal bone

The histopathological study of two cases of sudden deafness is presented. The temporal bones showed cochleosaccular abnormality. The most striking pathological changes were collapse of the organ of Corti, atrophy of the tectorial membrane, atrophy of the stria vascularis, decrease in the number of the cochlear nerves, collapse of the saccular membrane and partial absence of the sensory epithelial layer in the saccular macula. These changes are quite similar in type to those occurring in labyrinthitis of known viral etiology and to those in previously reported cases of sudden deafness which were assumed to be of viral origin. This evidence suggests that a viral infection was the most probable etiology of sudden deafness in these ears. In addition, unusual findings of endolymphatic hydrops limited to the extreme basal end of the cochlear duct were found in Case 1. A patent cochlear aqueduct and circumscribed perilymphatic labyrinthine ossification in the superior seimicircular canal were also observed. With these histopathological findings, the possibility of viral infection via the meninges as well as via the hematogenous route into the inner ear is proposed.

Histopathological findings in the inner ear caused by measles

An otopathological analysis of three cases of viral labyrinthitis was performed. Six temporal bones cut in serial sections were available for this study. According to the degree of degenerative changes in various parts of the inner ear two types of morphologically distinct labyrinthitis after measles are presented: the first one with the port of entrance through the internal auditory meatus and characterized by, first and most significantly, changes in the spiral ganglion cells; and the second, as described previously by Lindsay, with the port of entrance of the virus in the inner ear through the stria vascularis, with degenerative changes in various structures within the endolymphatic duct.

Vertigo of delayed onset after sudden deafness

An entity of episodic true vertigo of delayed onset following sudden and profound sensorineural hearing loss is described. Data on 12 patients and three case reports are presented. The latency between sudden deafness and the onset of the vertigo varied from 1 to 68 years. The vestibular symptoms are identical to the vestibular symptoms of Ménière's disease, and there is some evidence that endolymphatic hydrops in the previously deafened ear represents at least part of the labyrinthine pathology. Labyrinthectomy in the deaf ear was curative. Tentatively, this entity is best considered a variant of Ménière's disease.

Sudden deafness following cardio-pulmonary bypass surgery

A case is presented of sudden deafness following cardio-pulmonary bypass surgery. Microembolism is believed to be the most likely cause as this is common following the use of pump oxygenator systems. There was no response to anticoagulants.

Viral labyrinthitis -- an experimental study

Summary--An attempt was made to produce viral labyrinthitis in the rhesus monkey. Rhesus monkeys are susceptible to the mumps virus. Nine animals were used. After removal of the stapes, the left oval windows were plugged with Gelfoam soaked in a culture of live mumps virus; right oval windows were plugged with Gelfoam soaked in killed cultures. Animals were sacrificed at different time intervals, postinfection. In eight of the nine animals there was seroconversion from negative to positive; however, none of the animals developed the histologic changes of viral labyrinthitis.

Sudden deafness and labyrinthine window ruptures. Audio-vestibular observations

In 1971, one of the authors reported sudden deafness associated with labyrinthine window membrane ruptures. Eighteen additional cases have been explored surgically since then. Data on 21 cases are presented. Sudden profound cochlear deafness has now been encountered in 21 cases which were surgically explored. In 15 instances, fistulae of round, oval, or both windows were encountered and repaired. In 10 of the 15, there was a definite history of sudden exertion or trauma prior to onset. The oval window alone was ruptured in nine patients, the round window alone in one, and both windows were ruptured in five patients. The oldest patient was 62 years and the youngest 11 years of age. Differential audiological studies showed profound losses in all cases. Almost every case was studied by pure tone AC-BC and speech audiometry, Békésy, and impedance tests. Whenever possible other audiologic tests, such as recruitment, tone decay, and SISI were performed. These findings are presented in detail. Vestibular function was studied by electronystagmography (ENG) in 15 of the 21 cases surgically explored. There was evidence of vestibular dysfunction in almost every case with sudden hearing loss. Significant ENG details are presented. Surgical repairs of ruptured window membranes were followed by improvements in some of the patients. Postoperative audiologic data are presented. The theoretical aspects include discussion of possible cerebrospinal fluid (CSF) perilymph pathways between cochlear aqueduct and scala tympani and between internal auditory meatus and scala vestibuli. It is concluded that spontaneous labyrinthine window ruptures must now be added to the etiologic factors in “sudden hearing loss.” It is premature to set down criteria for surgical intervention in such cases. Further careful studies are necessary.