Histopathologic features of the temporal bone in usher syndrome type I.

Temporal bones of 2 patients with Usher syndrome type I were examined using light microscopy. In both patients, findings from histopathologic examination of the cochlea were characterized by degeneration of the organ of Corti, which was most marked in the basal turn, atrophy of the stria vascularis, and a decrease in the number of spiral ganglion cells. The cochlear nerve appeared to be diminished. The sensory epithelium of the saccular and utricular maculae of patient 1 was normal for age. The left temporal bone of patient 2, classified as Usher syndrome genetic subtype USH1D or USH1F, demonstrated the typical signs of severe cochleosaccular degeneration. Present cases and cases from the literature were reviewed in search of an explanation for the above-described differences in histologic findings.

Temporal bone pathology in a case of Cogan's syndrome.

Cogan's syndrome (CS) presents typical and atypical types. Typically, there are episodes of nonsyphilitic keratitis and audiovestibular dysfunction. Atypically, there are inflammatory changes in other eye structures and other organ systems, particularly the cardiovascular system. The temporal bone pathology in a case of CS shows changes that are similar to those observed in other autoimmune disorders associated with audiovestibular dysfunction. The following pathologic features characterize autoimmune inner ear disease: 1. acute labyrinthitis resulting in atrophy of inner ear tissues including the sense organs and their supporting structures; 2. endolymphatic hydrops; 3. focal and diffuse proliferation of fibrous tissue and bone; and 4. retrograde neuronal degeneration. These pathologic findings are consistent with an inflammatory (and possibly ischemic) attack on the membranous labyrinth.

Auditory and cytocochlear correlates of inner ear disorders.

Pure-tone threshold audiograms showing sensorineural hearing loss, when plotted on a data-based anatomic frequency scale, show a close spatial correlation with their respective cytocochleograms. Whereas most of the cochleae show pathology of several different cell types, a sufficient number show losses that involve predominantly a single cell type, which permits the following deductions: (1) focal lesions of the organ of Corti are strongly tonotopic and are responsible for those instances of abrupt pure-tone threshold losses; (2) lesions of the stria vascularis show no tonotopic organization but lead to flat pure-tone threshold losses; and (3) the principal effect of neuronal losses is a diminished capability for word recognition. There is an indeterminate group where no pathologic correlate can be identified by light microscopy.

[Spontaneous cerebrospinal fluid fistula in the tegmen tympani]. / Spontane Liquorfisteln im Tegmen tympani.

The author's experience with spontaneous cerebrospinal fluid (CSF) otorrhea from the tympanomastoid tegmen is based on the management of two clinical cases, the temporal bone histopathological findings in a third case suffering fatal meningitis and a review of the literature. Characteristically, the disorder occurs in otherwise healthy ears and is the consequence of embryogenic faults in the dura mater and adjacent tegmen. After years of exposure to physiologically normal CSF pressures, these faults may fistulize into the tympanomastoid compartment. The onset may be at any age, but is more common after age 40. About 20% of cases have a history of one or more bouts of meningitis. The site of the leak is characterized by one or more defects measuring 2-5 mm in the dura mater and adjacent bony plate, usually in the area of the petrous ridge. About 25% of defects are associated with small meningoceles or meningoencephaloceles. Computed tomographic and magnetic resonance imaging, as well as testing with fluorescein dye, provide confirming diagnostic data. Corrective surgery employs transmastoid exploration. After any existing meningoceles or meningoencephaloceles have been cauterized or amputated, small grafts of autogenous fascia or cartilage are used to plug defects found. The area is covered with temporalis fascia graft, reinforced by a pedicled muscle-fascia graft and, if needed to obliterate the mastoid cavity, a free graft of subcutaneous abdominal adipose tissue.

Pathology of prelingual profound deafness: magnitude of labyrinthitis fibro-ossificans.

Quantitative histologic studies were performed on 15 temporal bones from eight adult persons who were known to have prelingual bilateral profound hearing loss. The pathologic changes are characterized by severe degeneration of the structures of the cochlear duct, often with degeneration of the vestibular sense organs, causing a reparative host response that features osteoneogenesis and fibrous proliferation followed by retrograde neuronal degeneration. The pathology is consistent with meningogenic bacterial or viral labyrinthitis that occurred subclinically or went undiagnosed. Bone and fibrous tissue are present in varying extent in the scala tympani of 12 of the 15 temporal bones. Six cochleae from four subjects with fibro-osseous proliferation in the scala tympani extending as far as the ascending part of the basal turn have neuronal populations ranging from 963 to 5,355 (mean 2,826, 8% of neonatal normal, 35,500). In three cochleae from two subjects with no fibro-osseous proliferation in any area of the scala tympani the neuronal population ranges from 11,322 to 20,484 (mean 15,438, 43% of neonatal normal). Relative to cochlear implantation, computed tomographic imaging provides a means for determining the extent of fibro-osseous proliferation in the scala tympani, which in turn alerts the surgeon to surgical obstacles to optimal implantation as well as providing a basis for judging the extent of loss of cochlear neuronal population.

The National Temporal Bone, Hearing, and Balance Pathology Resource Registry.

The National Temporal Bone, Hearing, and Balance Pathology Resource Registry has been established with funding provided by the National Institute on Deafness and Other Communication Disorders of the National Institutes of Health. The registry is meant to serve as a national resource for researchers and the public to stimulate and facilitate human otopathologic research. It will maintain a computerized database of currently active and inactive temporal bone and auditory brain-stem collections throughout the United States. In addition, it will encourage human temporal bone research by disseminating pertinent information, developing and fostering temporal bone professional educational activities, implementing a national temporal bone acquisition network, and encouraging investigative collaborations in the study of the human temporal bone and brain structures. It will also identify otopathologic collections at risk of being discarded or lost and will develop mechanisms and strategies to conserve them.

Cochlear pathology in presbycusis.

A survey of the temporal bone collection at the Massachusetts Eye and Ear Infirmary reveals 21 cases that meet the criterion for the clinical diagnosis of presbycusis. It is evident that the previously advanced concept of four predominant pathologic types of presbycusis is valid, these being sensory, neural, strial, and cochlear conductive. An abrupt high-tone loss signals sensory presbycusis, a flat threshold pattern is indicative of strial presbycusis, and loss of word discrimination is characteristic of neural presbycusis. When the increments of threshold loss present a gradually decreasing linear distribution pattern on the audiometric scale and have no pathologic correlate, it is speculated that the hearing loss is caused by alterations in the physical characteristics of the cochlear duct, and the loss is identified as cochlear conductive presbycusis. It is clear that many individual cases do not separate into a specific type but have mixtures of these pathologic types and are termed mixed presbycusis. About 25% of all cases of presbycusis show none of the above characteristics and are classified as indeterminate presbycusis.

Myths in neurotology.

For many diseases the etiology of disordered function is unknown and therapy is either symptomatic or empirical. The empirical approach to therapy is acceptable to many physicians, particularly if a treatment can be based on some attractive, although unproven, concept of pathogenesis. A hypothetical explanation of disordered function can become widely popular in spite of a serious lack of scientific support. When evidence emerges that refutes the logic of a concept of pathogenesis, then that concept becomes a myth. Human temporal bone studies have identified several myths in neurotology that deserve our attention. Among these myths are the following: (1) cochlear otosclerosis is a common cause for sensorineural hearing loss, (2) idiopathic sudden sensorineural hearing loss is a vascular disorder that should be treated as a medical emergency, (3) the conductive component of hearing loss in Paget's disease is caused by ossicular fixation and therefore should be surgically correctable, (4) vascular loops should be considered as a possible cause for otherwise unexplained otologic symptoms, (5) surgical manipulations on the endolymphatic sac are scientifically sound therapies for selected cases of Meniere's disease, and (6) perilymph fistulas are a common cause for audiovestibular symptoms that are not related to a stressful incident.

Bilateral acoustic neurofibromatosis (neurofibromatosis 2): a disorder distinct from von Recklinghausen's neurofibromatosis (neurofibromatosis 1).

A case report of bilateral acoustic neurofibromatosis (NF-2) is presented with temporal bone histopathology. The distinct clinical and genetic features of NF-2 are reviewed in the context of recent data that show it to be a disorder distinct from classic von Recklinghausen's disease (NF-1).

Autosomal dominant sensorineural hearing loss. Pedigrees, audiologic findings, and temporal bone findings in two kindreds.

We report the clinical and otopathologic findings in three persons from two kindreds affected with adult-onset autosomal dominant progressive sensorineural hearing loss. The primary pathologic change is a deposit of acid polymucosaccharide ground substance in the cribrose areas; in the spiral ligament, limbus, and spinal lamina of the cochlea; and in the stroma of the maculae and cristae. These deposits obstruct the channels that accommodate the dendritic nerve fibers to the auditory and vestibular sense organs. The end result is strangulation and degeneration of dendrites followed by retrograde neuronal degeneration in association with varying degrees of atrophic change in the sense organs.

The anterior inferior cerebellar artery in the internal auditory canal.

It has been proposed that compression of the auditory and vestibular nerve trunks by vascular loops might be the cause of otherwise unexplained hearing loss, tinnitus, and vertigo, as well as Meniere's disease. We studied the human temporal bone histological collection at the Massachusetts Eye and Ear Infirmary to determine whether audiovestibular symptoms could be correlated with the presence of the anterior inferior cerebellar artery within the internal auditory canal. Anterior inferior cerebellar artery loops were found within the internal auditory canals of 12.3% of 1327 temporal bones, about half the number found when preparations with intact brains are studied. This difference can be attributed to avulsion of the anterior inferior cerebellar artery during removal of the brain at autopsy. There were 5 cases of unexplained unilateral hearing loss with anterior inferior cerebellar artery loops: 3 in the opposite ear and 2 in both ears. There were 2 cases with unilateral unexplained tinnitus with anterior inferior cerebellar artery loops: 1 in the involved ear and 1 in the opposite ear. A case with bilateral tinnitus had an anterior inferior cerebellar artery loop in 1 ear. There were 29 cases of vertigo with no peripheral histopathological correlate or central nervous system disorder; anterior inferior cerebellar artery loops were found in the internal auditory canals of 7 (12.5%) of the 56 ears in this group, which is not significantly different from the 12.3% incidence recorded for the entire collection. In 23 cases of unilateral Meniere's disease, there were anterior inferior cerebellar artery loops in the hydropic ears in 3, the opposite ear in 1, and both ears in 1. We can find no correlation between unexplained hearing loss, tinnitus, vertigo, or Meniere's disease and the presence of the anterior inferior cerebellar artery in the internal auditory canal.

Blockage of longitudinal flow in endolymphatic hydrops.

The external shunt operation on the endolymphatic sac is based on the concept that it will drain excess endolymph and thus arrest the progression of endolymphatic hydrops. We performed histological studies on 46 temporal bones from 13 cases of bilateral and 20 cases of unilateral Meniere's disease to evaluate the status of the pathways of longitudinal flow of endolymph to the sac. The endolymphatic ducts were blocked in 8 specimens (17%), the endolymphatic sinuses in 9 (19.5%), the utricular ducts in 12 (26%), the saccular ducts in 7 (15%), and the ductus reuniens in 27 (59%). These blockages arrested longitudinal flow from both the pars superior and inferior in 21 cases (46%), the pars superior only in 3 (6.5%), and the pars inferior only in 16 (35%). In the 6 ears with all pathways open, 2 were found to have fistulae between the saccules and the perilymphatic spaces, which theoretically results in internal shunting, thus alleviating the need for the external shunt procedure. In the aggregate, therefore, 42 (91%) of 46 ears showed either areas of blockage of longitudinal flow or internal shunts that would theoretically negate the value of external endolymphatic shunt procedures. These temporal bones, however, are from an autopsy population and the severity of pathological changes is probably greater than it would have been at an earlier age when external shunt surgery might have been a therapeutic consideration.

Delayed endolymphatic hydrops and its relationship to Meniére's disease.

Delayed endolymphatic hydrops (EH) can be characterized as having ipsilateral and contralateral types. They are similar in that both have early and late phases of otologic symptoms and that the early phase is a profound hearing loss in one ear. The late phases differ, however, in that the ipsilateral type develops the symptoms of EH (episodic vertigo) in the deaf ear and the contralateral type develops the symptoms of EH (fluctuating hearing loss and/or episodic vertigo) in the hearing ear. In more than half the cases of both types of delayed EH, the profound hearing losses in the early phase are simply discovered to be present in early childhood without a known time of onset. The temporal bones of two patients with contralateral delayed EH show pathologic changes in the deaf ears that are similar to those known to occur in mumps and measles labyrinthitis, whereas the pathologic changes in the hearing ears are similar to those known to occur in Meniere's disease. These observations support the proposition that Meniere's disease may occur as a delayed sequela of inner ear damage sustained during an attack of subclinical viral labyrinthitis occurring in childhood.

In search of cochlear morphologic correlates for tinnitus.

A correlative study was made of the cochlear pathologic features existing in the temporal bones of 83 subjects with a clinical history of tinnitus and 33 without tinnitus. None of 24 types of pathologic change assessed by light microscope occurred in more than 40% of tinnitus cases; nor was the prevalence of any of these pathologic changes significantly greater in subjects with tinnitus compared with control subjects. For five types of morphologic alteration the prevalence was significantly greater among control subjects compared with tinnitus cases, but this is interpreted cautiously because of the challenge in retrospectively selecting an appropriate control group. Under the conditions of the study, that is, using light-microscopic techniques on tissues obtained post mortem, we could not identify a pathologic correlate for tinnitus.

Pathology of peripheral vestibular disorders in the elderly.

A clinical classification of vertigo commonly seen in the elderly and caused by peripheral vestibular disorders is illustrated by case reports and temporal bone histopathology. The classification includes inducible transient vertigo and noninducible protracted vertigo. The peripheral vestibular pathology includes abnormalities of sensory, neural, and mechanical structures and is often asymmetric. The pathogenesis of these disorders is often speculative, but includes degenerative, infectious, neoplastic, and vascular insults to the vestibular labyrinth.