Petrous apex cholesterol granuloma: pictorial review of radiological considerations in diagnosis and surgical histopathology.

BACKGROUND: Petrous apex cholesterol granulomas are expansile, cystic lesions containing cholesterol crystals surrounded by foreign body giant cells, fibrous tissue reaction and chronic inflammation. Appropriate treatment relies on an accurate radiological diagnosis and an understanding of the distinguishing radiological features of relevant entities in the differential diagnosis of this condition. METHODS: Firstly, this paper presents a pictorial review of the relevant radiological features of petrous apex cholesterol granuloma, and highlights unique features relevant to the differential diagnosis. Secondly, it reviews the histopathological and radiological findings associated with surgical drainage of these lesions. RESULTS: Radiological features relevant to the differential diagnosis of petrous apex cholesterol granuloma are reviewed, together with radiological and histopathological features relevant to surgical management. Following surgical management, histopathological and radiological evidence demonstrates that the patency of the surgical drainage pathway is maintained. CONCLUSION: Accurate diagnosis of petrous apex cholesterol granuloma is essential in order to instigate appropriate treatment. Placement of a stent in the drainage pathway may help to maintain patency and decrease the likelihood of symptomatic recurrence.

The intravestibular source of the vestibular aqueduct: Its structure and pathology in Ménière's disease.

CONCLUSION: We describe a thin, highly vascular layer of mineralized cartilage, which surrounds most of the endolymphatic duct. In the normal ear this may act in helping to control the chemical composition of endolymph. In Ménière's disease (MD) there is a marked apoptotic change among the mineralized cartilage cells of this layer, which seems to be associated also with the deposition of a pathological substance in the walls of many blood vessels. This may lead to serious chemical change in the nearby endolymph and so provoke the symptoms of MD. OBJECTIVES: Endolymphatic hydrops is found in all cases of MD, but is not specific for that condition. We sought a cellular change in the vicinity of the saccule that might be more specific than the lesion of endolymphatic hydrops and thus lead to a more successful management of the disease. MATERIALS AND METHODS: We examined stained step sections of 33 autopsy temporal bones from 20 cases of MD, particularly in the region of the vestibule, and compared the changes with those found in a similar region of 65 temporal bones taken from randomly selected cases of non-Ménière conditions. RESULTS: In all temporal bones there was a well-demarcated region of the posterior vestibule, which formed a skeletal arch around the opening of the tunnel of the vestibular aqueduct into which the endolymphatic duct entered from the vestibule. This 'vestibular arch' was composed mainly of blood vessels and mineralized chondrocytes. The inner skeletal layer surrounding the course of most of the endolymphatic duct in the tunnel of the vestibular aqueduct was composed of the same tissue and was in fact continuous with the vestibular arch. In the non-Ménière temporal bones the mineralized chondrocytes were congregated around normal thin-walled blood vessels and small numbers of them seemed to be undergoing apoptosis in this vicinity. In all of the MD temporal bones, except five in which the vestibular arch was either absent or atrophic, we found pronounced changes of apoptosis among the mineralized cartilage cells and these were associated with proliferative changes in blood vessels in which a bluish-staining translucent deposit, possibly mineralization of the vascular wall, was prominent.

Possible role of biofilm in fulminant meningitis related to cochlear implantation of dysplastic inner ear.

UNLABELLED: Thanks to improvements in device design and surgical procedures, the number of potential candidates for cochlear implantation has been growing to include patients with inner ear malformations. Many precautions are taken pre-, peri- and postoperatively for these patients given the increased risk of surgical and medical complications, but with the rising bacterial resistance to antibiotics and the discovery of biofilm as a probable cause of chronic infections, postoperative morbidity remains higher than desired. OBJECTIVE: The purpose of this investigation is to describe histological findings on a temporal bone from a 2-year-old infant with a cochlear implant and an inner ear deformity who died of bacterial meningitis. MATERIALS AND METHODS: The patient's temporal bone was studied under light microscopy, the cochlear implant studied with a scanning electron microscope, and later subjected to in situ hybridization to find bacterial DNA. RESULTS: The scanning electron microscopy image shows cellular formations on the surface of the implant, which later binds to the probe used for the in situ hybridization. CONCLUSION: There is evidence that bacterial DNA is present on the electrode array, which suggests existence of biofilm formation on the cochlear implant surface.

Cholesteatoma behind an intact tympanic membrane: histopathologic evidence for a tympanic membrane origin.

BACKGROUND: Several theories have been proposed with respect to the origin and pathogenesis of cholesteatoma behind an intact tympanic membrane. CASE REPORT: The authors describe a case of cholesteatoma behind an intact tympanic membrane in a 71-year-old man with a history of tympanic membrane retraction fixed to the incus without evidence of a perforation. The membrane eventually became detached, and remnants of keratinizing squamous epithelium were found on the incus. DISCUSSION: Mechanisms such as metaplasia, ectopic epidermis rests, or ingrowth of meatal epidermis have been proposed to explain the pathogenesis of cholesteatoma behind an intact tympanic membrane. These findings, based on temporal bone histopathology, support the role of an acquired epidermal rest. CONCLUSIONS: This case report provides evidence that cholesteatoma behind an intact tympanic membrane can be established from a resolved retraction of the pars tensa of the tympanic membrane.

Myelination of the human auditory nerve: different time courses for Schwann cell and glial myelin.

The goal of this study was to trace the development of myelin in the human auditory nerve. To do this, we used the Woelcke iron-hematoxylin technique to stain myelin sheaths in sections from fetal temporal bones and brain stems. In the cochlea, aggregations of Schwann cells are seen in the modiolus and along the spiral lamina by the 15th fetal week. By the 22nd fetal week, dense arrays of stained Schwann cells are present on auditory nerve axons within the temporal bone. By the 24th fetal week, light myelin sheaths extend up to, but not beyond, the glial junction. Myelin sheaths are not present in the auditory nerve central to the glial junction until the 26th fetal week or later. These results demonstrate a gap of several weeks between the onset of Schwann cell myelination distally and glial myelination proximally. The period between these two events may represent the time of final maturation of the organ of Corti.

Mitochondrial cytochrome oxidase immunolabeling in aged human temporal bones.

Presbycusis, an age-related hearing loss, is accompanied by histopathological cochlear changes including variable amounts of degeneration of the auditory receptors, neurons and the stria vascularis. The causes of degeneration are unknown, although acoustic trauma and exposure to ototoxic agents are certainly contributors to the cellular degeneration. Acquired mitochondrial DNA defects are postulated as important determinants of aging in neuromuscular tissues. The cochlear neurons are highly metabolic and are, therefore, likely to be affected by mitochondrial DNA defects. Sequence analysis has demonstrated a significant number of acquired mutations in the cytochrome oxidase gene in the neurons from aged human cochleas. The current study used immunohistochemical labeling of cytochrome oxidase in the neuronal cell bodies in archival celloidin sections to evaluate relationships among label density, hearing loss, number of neurons and mitochondrial DNA changes within individual cochleas. Label density was less in many aged temporal bones, but not all. There was no relationship among any other variables. It is concluded that while there may be a decrease in the amount of cytochrome oxidase expression in aged spiral ganglion cell bodies, there are many other factors that contribute to hearing loss and cellular degeneration.

Idiopathic sudden sensorineural hearing loss: temporal bone histopathologic study.

We microscopically examined the temporal bones of 12 ears with idiopathic sudden sensorineural hearing loss (iSSNHL), 10 ears with presbycusis, 11 ears with normal hearing, and 8 unaffected contralateral ears of patients with iSSNHL. The degeneration of the spiral ligament, vascular stria, hair cells, dendrites, and apical spiral ganglion cells was greater in ears with iSSNHL than in the other groups. The apical ganglion cells were significantly more affected than the basal ganglion cells, and the spiral ganglion cell loss increased as a function of duration of iSSNHL. Cochlear ossification was found in 1 ear with iSSNHL, and hydrops in 2. These findings suggest a viral rather than a vascular or ruptured inner ear membrane origin for iSSNHL.

Auditory perception in vestibular neurectomy subjects.

The auditory efferent nerve is a feedback pathway that originates in the brainstem and projects to the inner ear. Although the anatomy and physiology of efferents have been rather thoroughly described, their functional roles in auditory perception are still not clear. Here, we report data in six human subjects who had undergone vestibular neurectomy, during which their efferent nerves were also presumably severed. The surgery had alleviated these subjects' vertigo but also resulted in mild to moderate hearing loss. We designed our experiments with a focus on the possible role of efferents in anti-masking. Consistent with previous studies, we found little effects of vestibular neurectomy on pure-tone detection and discrimination in quiet. However, we noted several new findings in all subjects tested. Efferent section increased loudness sensation (one subject), reduced overshoot effect (five subjects), accentuated 'the midlevel hump' in forward masking (two subjects), and worsened intensity discrimination in noise (four subjects). Poorer speech in noise recognition was also observed in the surgery ear than the non-surgery ear in three out of four subjects tested, but this finding was confounded by hearing loss. The present results suggest an active role of efferents in auditory perception in noise.

The Clarion electrode positioner: temporal bone studies.

OBJECTIVE: To study the relationship of the Clarion electrode to the modiolus when using an intracochlear positioner. BACKGROUND: There are theoretical advantages to positioning a cochlear implant electrode in close proximity to the modiolus. This may allow more focused, discrete fields of electrical current, reducing both requirements to achieve threshold and the channel interactions associated with the simultaneous and nonsimultaneous stimulation of closely spaced electrodes. METHODS: Ten fresh temporal bones were used to assess the position of the electrode in the scala tympani with the positioner in place. The bones were X-rayed after implantation. The relationship of the electrode to the modiolus was studied by calculating a ratio between the curve assumed by the electrode in relationship to the outer wall of the cochlea. The depth of insertion was evaluated in degrees or number of turns around the modiolus. RESULTS: The electrode was brought closer to the modiolus and a greater depth of insertion was achieved in all cases with the positioner. CONCLUSION: The intracochlear positioner is capable of bringing the electrode consistently closer to the neural elements within the modiolus.

Extraneous round window membranes and plugs: possible effect on intratympanic therapy.

Recently there has been increasing interest in the possibility of treating inner ear disorders by application of medication into the middle ear on the premise that it will diffuse through the round window membrane into the inner ear. We examined 202 temporal bones from 117 patients to determine the frequency of round window niche obstruction. Patients ranged in age at the time of death from 31 to 97 years. Eleven percent of the ears were found to have fibrous tissue or a fat plug, and 21% had an extraneous (false) round window membrane. Of the 85 patients from whom both temporal bones were examined, 56% had no obstruction in either ear, while 22% had obstruction in both ears. We conclude that anatomic variations of the round window niche may explain the wide variations found in dosage of medication required to produce a clinical result.

Coexpression of neurotrophic growth factors and their receptors in human facial motor neurons.

Neuronal development and maintenance of facial motor neurons is believed to be regulated by neurotrophic growth factors. Using celloidin-embedded sections, we evaluated immunoreactivity of 11 neurotrophic factors and their receptors in facial nuclei of human brain stems (4 normal cases, and 1 from a patient with facial palsy and synkinesis). In the normal subjects, positive immunoreactivity of the growth factor neurotrophin-4 and acidic fibroblast growth factor (aFGF) was observed in facial motor neurons, as was positive immunoreactivity against ret, the receptor shared by glial cell line-derived neurotrophic factor and neurturin. Immunoreactivity was moderate for the receptor trkB and strong for trkC. In the case of partial facial palsy, surviving cells failed to show immunoreactivity against neurotrophins. However, immunoreactivity of aFGF was up-regulated in both neuronal and non-neuronal cells in this patient. Results suggest that these trophic growth factors and their receptors may protect facial neurons from secondary degeneration and promote regrowth of the facial nerve after axotomy or injury.

Meniere's disease and endolymphatic hydrops without Meniere's symptoms: temporal bone histopathology.

We studied temporal bone histopathology in 21 ears with Meniere's disease and 24 ears with endolymphatic hydrops without Meniere's symptoms and compared the findings to those in 10 ears with presbycusis and 11 ears with normal hearing. Normal hearing ears showed less degeneration of cochlear structures than the other ears. In ears with endolymphatic hydrops without Meniere's symptoms, the degeneration of spiral ligament, hair cells, dendrites (peripheral processes) and apical spiral ganglion cells was more severe than in the other three groups. In ears with Meniere's disease and endolymphatic hydrops without Meniere's symptoms, the hair cells and dendrites were more affected than ganglion cells and there was no correlation between hair cell and ganglion cell degeneration. These findings suggest that a permanent threshold shift in late stage endolymphatic hydrops is not related to ganglion cell loss but rather to degeneration of sensory elements.