The pathology of sudden deafness

Medical management of sudden hearing loss

A hurdle in the evaluation of any therapy of ISHL has previously been proposed-a spontaneous recovery of satisfactory hearing of 63% of patients. The hurdle has yet to be convincingly passed by any drug therapy. The intent here is not to denigrate the use of drugs in this syndrome; on the contrary, it remains likely that some subgroups of ISHL would benefit from specific medical management. For instance, a systemic viremia would be most logically treated with anti-inflammatory agents and a thrombotic event with anticoagulants. However, prospective studies in which patients are divided into prognostic categories before treatment with adequate control groups must be performed.

The effects of vascular occlusion on the human inner ear

Occlusion of the anterior vestibular artery has resulted in severe degeneration and new bone formation limited to the utricle, saccule, and superior and lateral semicircular canals. Depriving the inner ear of its main blood supply, i.e. the internal auditory artery, has resulted in severe degeneration and ossification of the entire membranous labyrinth, except the endolymphatic duct and sac. A more severe cochlear sclerosis was seen when both arterial and venous blood supplies to the cochlea were occluded. The implications of these findings on the etiology and management of inner ear disorders are emphasized.

Cochlear hearing loss and viral infection

A group of about 100 consecutive patients admitted to an otorhinolaryngological outpatient department for treatment of cranial nerve affections underwent detailed neurological, audiological and laboratory examinations. Of 34 patients with hearing loss, objective signs of viral infection were found in 12. The hearing loss was sensorineural of the cochlear type, in 7 cases of the high-frequency type, in 5 cases of the low-frequency (Menière) type. Within one year after the onset of the disease the hearing loss had disappeared in all but 2 cases. Reversible dysfunction of two or more cranial nerves was found in 7 of 8 cases examined. In the cerebrospinal fluid the cell count and the total protein and gamma-globulin values were increased in most patients. Our findings indicate a reversible sensorineural hearing loss to be part of a viral-induced meningoencephalitis and cranial polyneuropathy. The mechanism of the reversible low- and high-frequency hearing loss is discussed.

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.

Hearing loss as a sequela of meningitis

A retrospective study of 547 cases of meningitis was performed. Of these, 236 were bacterial, 304 were viral, and 7 were fungal in etiology. Of 110 survivors of bacterial meningitis over the age of 2 1/2 years, 23 or 21% suffered partial or complete sensorineural hearing loss. The site of auditory injury in cases of partial loss was the cochlea by audiologic criteria. A positive correlation with hearing loss was found for the species of organism, delay before treatment, low CSF sugar, and CSF pleocytosis. Of 7 patients with fungal meningitis, 3 suffered hearing loss with signs of a retrocochlear site. Of 304 cases of aseptic meningitis, none developed a hearing loss. The pathophysiology of hearing loss as a sequela of meningitis and the possible explanations for absence of hearing loss in viral meningitis are discussed.

The nystagmus and the therapeutic effects on early-diagnosed cases of sudden deafness

We investigated the hearing prognoses of early diagnosed cases of sudden deafness. We tried to find the most reliable factor to determine the prognosis of hearing loss. Of various possibilities that affect the prognosis; the period of onset to first examination, therapeutic manner and vestibular test findings, the findings of caloric test and spontaneous nystagmus showed much better correlation with the hearing prognosis than others. Thus, we presume the vestibular dysfunction in cases of sudden deafness may reflect the extension and severity of inner ear involvement.

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 and vaccination

A 16-year-old female developed sudden unilateral deafness and acute vertigo two days after routine revaccination against tetanus and diphtheria. Eight other cases culled from the literature are reviewed, and the symptoms and findings from the VIIIth cranial nerve discussed. It is postulated that a local hypersensitivity reaction may account for this and some other forms of sudden sensorineural deafness.

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.

Inner ear degeneration in acoustic neurinoma

The temporal bones of three cases of acoustic neurinoma are described to illustrate histopathological features of inner ear lesions due to chronic partial obstruction of blood circulation by the tumor in the internal auditory meatus. Degenerative changes in the inner ear due to acoustic neurinoma were evaluated and compared with changes in the opposite ear. The main pathological findings in the inner ear which were attributed to the tumor were degeneration of nerve fibers and of ganglion cells, degeneration of the stria vascularis, degeneration of the tectorial membrane, fibrosis and ossification of a semicircular canal. Fairly good preservation of sensory cells was observed in the presence of total degeneration of nerve fibers and ganglion cells and subtotal degeneration of the stria vascularis.

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.

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.

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.