Inner ear pathology of sudden deafness. Histopathology of acquired deafness in the adult coincident with viral infection

Mean platelet volume: is it a predictive parameter in the diagnosis of sudden sensorineural hearing loss?

The mean platelet volume (MPV) is associated with increased platelet reactivity and increased atherothrombosis. High MPV values are a risk factor for thrombotic vascular diseases. Our aim was to investigate whether a relationship exists between sudden sensorineural hearing loss (SSHL) and a high MPV value. The records of 46 patients who were admitted to the ENT (ear nose throat) ward for SSHL and received medical treatment and 46 patients in a control group were retrospectively screened. The correlation among the levels of the MPV, the number of platelets, and SSHL were evaluated in the two groups. The ages, genders, and the platelet count values of the patients showed a normal distribution in both groups. No significant difference was found for the MPV values between the groups. The MPV is not a predictive parameter in the diagnosis of SSHL.

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.

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.

Acute measles infection in the hamster cochlea

Measles virus has been implicated in sudden sensorineural hearing loss (SNHL) in adults as well as in children. Furthermore, sensorineural hearing loss following live measles virus vaccination has been reported. As of yet, however, there has been only few reports on human temporal bone pathology due to measles, and on experimental animal models of measles infection. This study was undertaken to examine acute measles infection in adult hamster cochlea morphologically and immunohistochemically for precise understanding of this viral infection. Atrophy of the stria vascularis, loss of the organ of Corti, "rolled-up" tectorial membrane, and cell infiltration with a positive immunofluorescent reaction primarily within the scale media indicating endolymphatic labyrinthitis were the principal findings. These results were generally consistent with previous ones on human temporal bone pathology not only due to measles but also to SNHL. We consider measles virus to be one of the possible pathogens, even if low in frequency, causing profound and irreversible hearing loss, including SNHL. Completion of measles vaccination without complication and selective or mass revaccination may be necessary to prevent such hearing loss.

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.

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.

Effect of upper respiratory infection on hearing in the ferret model

In an effort to develop an adult animal model for acquired viral-induced hearing loss, three groups of mature ferrets were inoculated intranasally with respiratory viruses (influenza A/Port Chalmers, influenza B/Mass, and parainfluenza I), which have been implicated as causative agents in idiopathic sudden hearing loss (ISHL). All ferrets challenged with influenza A/Port Chalmers (A/PC) exhibited clinical signs of infection, but neither of the other two groups exhibited such signs. Conductive and/or sensorineural hearing losses were demonstrated in eight of 15 ferrets challenged with influenza A/PC and four of 10 ferrets in the group challenged with influenza B/Mass by brainstem auditory-evoked responses (BAERs) and acoustic immittance. None of the four ferrets infected with parainfluenza I demonstrated auditory dysfunction. When auditory changes were observed, nasal washes were performed, and tissues of the middle and inner ears were collected for viral assay and morphologic examination. All ferrets demonstrating auditory changes were shown to be infected by isolation of virus from nasal tissues. Virus was isolated from eustachian tube tissue in six of the eight ferrets infected with influenza A/PC, which also demonstrated altered BAERs and one of the four infected with influenza B/Mass, which also had auditory changes. Virus was isolated from the middle ear of two ferrets infected with influenza A/PC and from the inner ear of another two ferrets from the same group. These data suggest that influenza A/PC has a greater effect on auditory function in the ferret model than either influenza B/Mass or parainfluenza I and that the ferret may be an appropriate adult model to examine the etiologic role of viral upper respiratory tract infections in some acquired hearing impairments.

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.

Experimental Sendai virus-induced labyrinthitis in guinea pigs. An ultrastructural study of cochlear lesions

Guinea pigs were inoculated with a Sendai virus into the scala tympani and subsequent pathological changes of the cochleas were investigated by electron microscopy. Replication of the virus was indicated by buddings at the endolymphatic surface and by the intracytoplasmic occurrence of filamentous substances, ie, nucleocapsids. Budding viruses or free virus particles observed in a series of our experiments were identified as Sendai viruses by means of the immunological labeling with ferritin. Viral lesions, which were defined as the pathological changes of the cells associated with virus multiplication, were found in eight cochleas out of 20. This study revealed that the early lesions of the cochleas infected by Sendai viruses were primarily confined to Reissner's membrane and the stria vascularis, but the sensory cells were not affected.

Deafness in cryoglobulinemia

We present a histopathological study of 44-year-old female with essential cryoglobulinemia. She had suffered from purpura and ulcer in winter, bilateral tinnitus and progressive hearing loss. An audiogram taken a week before her death showed bilateral total deafness. In the cochlea of the left temporal bone, the organ of Corti was either missing or present as a mound. The stria vascularis was atrophic throughout the cochlea. The tectorial membrane showed drooping and encapsulation. Reissner membrane was in the normal position. Eosinophilic precipitate was noted in the scala media at the site where Reissner membrane bulged. The spiral ganglion cells were well preserved. In the lower basal turn, there was fibrosis and ossification intermingled in the scala tympani. Ossification was most marked near the basal end. The semicircular canals and vestibule were almost totally ossified and fused with surrounding bone. There was a small, cyst-like structure in the vestibule containing eosinophilic fluid. Our findings indicate that the deafness was the result of circulatory disturbance due to cryoglobulinemia. To our knowledge, this is the first cryoglobulinemia case in which temporal bone findings are reported.

Cochlear nerve fiber populations in 25 patients with profound deafness due to Menière's disease or sudden deafness

Surgical biopsy specimens of the cochlear nerve from 19 patients with Menière's disease and six patients with sudden deafness were studied. The total number of myelinated nerve fibres in the transverse fascicular area of each nerve were counted and the results were correlated with the clinical and preoperative audiological data. The total number of cochlear neurons in patients with Menière's disease ranged from 5,760 to 27,722 and in patients with sudden deafness from 8,500 to 22,714. The long duration of the disease or absent speech discrimination appeared not to be connected with lower numbers of neurons than preserved speech discrimination or short history of the disease.

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.

Sudden deafness in relapsing polychondritis. A scanning electron microscopy study

The left ear of a 57-year-old female who suffered sudden deafness during the course of relapsing polychondritis was examined under a scanning electron microscope. Marked degeneration of the organ of Corti in all turns and dislocated and encapsulated tectorial membrane were found in the cochlea. Marked decrease in number of the sensory cells in the utricular and saccular maculae and total loss of sensory hair bundles in the ampullary cristae of the semicircular canals were seen in the vestibule. These findings strongly suggest that the cause of sudden deafness in this case might be viral. The usefulness of scanning electron microscopy in human temporal bone pathology is stressed.

Single-cell layer membrane covering the degenerated cochlear duct after perilymphatic perfusion of streptomycin

Ultrastructural changes of the extrasensory epithelium in the scala media of guinea pig cochleae were observed from 3 to 137 days after perilymphatic perfusion with 20% streptomycin. The degeneration started in the organ of Corti, progressed to the interdental cells and roots of the outer sulcus cells and finally involved other epithelial cells such as Claudius and the inner and outer sulcus cells. In the final stage, except for the stria vascularis and Reissner's membrane, all epithelial cells which lined the cochlear duct were replaced by a single-cell layer membrane which originated medianly from the epithelial cells of Reissner's membrane and laterally from the superficial outer sulcus cells.

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.

Electron microscopic observations in a case of long-standing profound sensorineural deafness

The ultrastructural pathology in an ear with long-standing profound deafness is presented. Endolymphatic hydrops was present, although there had been no vestibular symptoms. Although hair cells were absent, the intercellular junctional complex at the endolymphatic surface of the organ of Corti was maintained, suggesting "healing" by migration or proliferation of supporting cells to fill the empty spaces. Severe atrophy of the stria vascularis was present, and crystalline deposits were found within the strial remnant. An encapsulated tectorial membrane was interpreted in light of ultrastructural findings as either herniation of the fibrillar connective tissue of the spiral limbus into the scala media or alternatively demonstrating abnormal continuity between the connective tissue of the spiral limbus and the remnant of tectorial membrane. Neural degeneration was severe in all cochlear turns. However, more nerve fibers were seen in the proximal portion of Rosenthal's canal than at the habenula perforata or in the organ of Corti, and central processes from the ganglion area were more numerous than peripheral processes. The ganglion cell population was reduced to approximately 10% of normal, and only unmyelinated cell bodies were found. Few recognizable neural fibers were seen within the organ of Corti, although bizarre collections of apparent cellular debris and cell processes containing many mitochondria or vesicles were seen in regions normally containing neural fibers.

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.

Sudden deafness. A histopathological study

Histopathological studies were performed in the temporal bones from a 77-year-old woman who had bilateral sudden deafness 31 years before her death. The common findings in both cochleas were atrophy of the organ of Corti and stria vascularis, and degeneration of the tectorial membrane. Pathology of the tectorial membrane consisted of atrophy and droplet formation of the middle and marginal zones. In one area, an atrophied tectorial membrane was lifted up by a mass on the limbus. The saccular wall in the left temporal bone was ruptured. There was no pathology in the vascular system in the labyrinths except for moderate degeneration of sensory epithelium. The pathogenesis of sudden deafness was discussed in the light of the present findings. Alteration of the tectorial membrane seemed to be the main factor as a possible cause of sudden deafness. Histopathological findings were reviewed from the literature.

Sudden deafnfess of vascular origin: a human temporal bone study

Temporal bone changes are described in a 57-year-old man who had sudden onset of dizziness and unilateral deafness two months before death. The patient suffered from hypertension, and congestive and renal failure. At autopsy, subarachnoid hemorrhage with punctate cortical hemorrhages and arteriolar thickening involved the right superior cerebellar hemisphere. The pathological changes involved primarily the right cochlea, saccule and posterior ampulla, and were consistent with vascular embarrassment of the temporal bone of two months duration. The cochlea demonstrated total loss of the organ of Corti and severe degenerative changes of the stria vascularis, spiral ligament, outer sulcus cells and distal cochlear nerve fibers. The saccule demonstrated loss of its macula and nerve fibers. The posterior ampulla showed evidence of previous rupture of its membranous wall with fibrosis and beginning bone formation. Fresh hemorrhage, present in some areas of both temporal bones, was related to the patient's terminal subarachnoid hemorrhage.

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.