The lateral skull base: a vascular perspective with clinical implications

The growing number of options in the surgical management of skull base disease has renewed interest in the microvascular anatomy of the lateral temporal region. We studied this anatomy by injecting colored solutions of methyl methacrylate into the major blood vessels of six human cadaver heads or selectively into their major branches. We used several techniques to see the vascular anatomy and to study its relationship to the layers of the scalp. Results revealed that every anatomically named blood vessel was accompanied by a finer, deeper blood vessel supplying the periosteum and outer table of the skull. These vessels arborized into a network of capillaries in the periosteum adherent to the outer bony cortex, from which we saw tiny perforators entering bone. This layered blood supply has direct implications for both ablative and reconstructive surgery for skull base disease. We also saw a previously undescribed arterial plexus accompanying the commonly described venous plexus in the infratemporal fossa.

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

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.

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.

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.

Cochlear implant. Histopathological guide to indications and contraindications: a post mortem study on temporal bones

We have studied the temporal bones of 4 deceased donors, individuals one with cochlear saccular degeneration, another with Mondini dysplasia, another with an ossification of the basal turn of the cochlea and the round window, post meningitis and the fourth who was implanted 10 years before. The indications and contraindications for cochlear implant placement are discussed.

Neurofibromatosis and brainstem implants: what to do?

The histopathological changes in the temporal bones of one donor individual deceased for complications of neurofibromatosis type 2 are studied. The different modalities of presentation of neurofibromatosis and the criteria for the differential diagnosis are presented. The possibilities of the auditory brainstem implants in this pathology are discussed.

Acoustic neuromas and meningiomas. Histopathological aspect: a post mortem study on temporal bones

The histopathological changes in the temporal bones of three deceased donors individuals, two with concomitant acoustic tumors and one with concomitant petroclival meningioma have been studied. The differences between neuromas and meningiomas are examined. The different clinical relevance and the different therapeutic guidelines are discussed.

Otosclerosis and cochlear otosclerosis: a post mortem study on temporal bones

We have chosen among many temporal bones of donors deceased individuals with concomitant otosclerosis, three particular cases, one with classic otosclerosis, another with cochlear otosclerosis with concomitant oval window ankylosis and another with cochlear otosclerosis without stapes fixation. The different histopathologic features are discussed and clinical and therapeutical guidelines are proposed.

Chronic otitis media: histopathological changes: a post mortem study on temporal bones

The temporal bones of 4 deceased individuals, with concomitant chronic otitis media are studied. The various histopathological changes in the middle ear cleft are examined: suppuration, polyps, granulation tissue. The possibilities of spontaneous healing of a perforated TM and the indications of surgical treatment are discussed.

Ménière's disease. Histopathological changes: a post mortem study on temporal bones

The histopathological changes in the temporal bones of two deceased donors individuals with concomitant Ménierè's disease have been studied. In one temporal bone we have found a blockage of the endolymphatic duct by abnormal bone. The histopathological modifications and the different therapeutic options are discussed. Clinical guidelines are proposed.

Cholesteatomatous otitis media: histopathological changes. A post mortem study on temporal bones

The histopathological changes in the temporal bones of 3 deceased donors individuals with concomitant chronic cholesteatomatous otitis media have been studied. The different forms of cholesteatoma are analyzed: the primary congenital, the primary acquired and the secondary acquired. The different clinical relevance and the different therapeutic guidelines are discussed.

Cholesterol granuloma of the petrous apex. A post mortem study on temporal bones

Otitis media (OM) is an infection localized in the middle ear: mastoid, middle ear cavity, Eustachian tube. The classification of OM includes otitis media with effusion, otitis media without effusion, and chronic otitis media. A rare complication of chronic otitis is cholesterol granuloma of the petrous apex. It may develop in any aerated portion of the temporal bone but most commonly develops when a pathologic process obstruct the air cell tracts to the petrous apex preventing normal aeration.

Acute otitis media. Histopathological changes: a post mortem study on temporal bones

A classification of otitis media is proposed and the histopathological changes of otitis media with effusion are reviewed post mortem on two temporal bones. A case of adhesive otitis media is observed on temporal bone slides. The clinical and therapeutic aspect are examined and treatment guidelines are proposed.

Application of labeling techniques to archival temporal bone sections

Pathology of the human inner ear has traditionally been studied in celloidin-embedded, hematoxylin and eosin-stained sections of the temporal bone. Although the traditional histologic approach has yielded valuable information, it is now possible to extend these studies to include analysis of molecules using immunohistochemical and histochemical staining techniques. Fourteen antibodies and 6 lectins have been applied to 420 archival, celloidin-embedded human temporal bone sections. Tissues had been fixed in 10% formalin, embedded in celloidin, sectioned, and stored for as many as 40 years. The staining intensities varied among sections, so they were ranked from 'no label" to "dense label." To investigate the relationships between the extent of postmortem changes (PMCs), storage time, and staining intensity for each antibody, the sections were graded according to their PMCs, which ranged from good preservation of the temporal bone histologic structure to severe postmortem autolysis. Although statistical analysis indicated that both extent of PMCs and storage time in general decrease the staining intensity, both poorly fixed tissue and sections stored for a long time can yield good immunostaining results with some antibodies.

Mutations in a novel cochlear gene cause DFNA9, a human nonsyndromic deafness with vestibular dysfunction

DFNA9 is an autosomal dominant, nonsyndromic, progressive sensorineural hearing loss with vestibular pathology. Here we report three missense mutations in human COCH (previously described as Coch5b2), a novel cochlear gene, in three unrelated kindreds with DFNA9. All three residues mutated in DFNA9 are conserved in mouse and chicken Coch, and are found in a region containing four conserved cysteines with homology to a domain in factor C, a lipopolysaccharide-binding coagulation factor in Limulus polyphemus. COCH message, found at high levels in human cochlear and vestibular organs, occurs in the chicken inner ear in the regions of the auditory and vestibular nerve fibres, the neural and abneural limbs adjacent to the cochlear sensory epithelium and the stroma of the crista ampullaris of the vestibular labyrinth. These areas correspond to human inner ear structures which show histopathological findings of acidophilic ground substance in DFNA9 patients.

Mastoid size and otitis media with effusion: question of correlation

OBJECTIVES/HYPOTHESIS

To determine the incidence of otitis media (OME) with effusion on histologic examination in temporal bones with mastoid cavities reduced by the fenestration procedure for otosclerosis.

STUDY DESIGN

Temporal bone histologic study.

METHODS

Light-microscopic examination of serially sectioned temporal bones.

RESULTS

The incidence of otitis media with effusion in temporal bones with prior fenestration operation was not any more frequent than the control group of temporal bones with surgically unaltered mastoid cavity.

CONCLUSIONS

There is no increased incidence of otitis media with effusion in temporal bones with prior fenestration operation.

Autonomic innervation of the human middle ear: an immunohistochemical study

PURPOSE

Although there have been numerous studies of autonomic innervation of the middle ear mucosa, and the mechanism of effusion into the middle ear cavity in animals, the autonomic innervation of the human middle ear has not received much attention. The purpose of this study is to show the presence of catecholaminergic nerve fibers in the human middle-ear mucus membrane that may play an important role in the pathogenesis of middle-ear effusion.

MATERIALS AND METHODS

A total of 126 celloidin-embedded temporal bone sections from the temporal bone bank at the House Ear Institute were used for immunohistochemical study. A polyclonal antibody to tyrosine hydroxylase enzyme was used to show the presence of catecholaminergic nerve fibers.

RESULTS

Tyrosine hydroxylase immunoreactive nerve fibers containing numerous fine varicosities along their course, characteristic of noradrenergic neurons, were observed throughout the middle-ear mucosa including the promontary, sinus tympani, mesotympanum, and hypotympanum. In addition, these nerve fibers were seen in close promixity to the small-caliber blood vessels. A striking variation in the intensity of staining as well as in the amount of nerve fibers was observed among the temporal bone sections.

CONCLUSION

It is possible that the catecholaminergic nerve fibers, like elsewhere in the body, may exert a direct influence on the middle-ear mucosal blood vessels. We speculate that the effusion into the middle-ear space is an active, rather than a passive process. It is conceivable that cholinergic-sympathetic nerves might exist in the human middle-ear mucus membrane, and that these autonomic nerves, in conjunction with the neuropeptides, may play an active role in the pathogenesis of human middle-ear effusion.

Morphology of the developing human endolymphatic sac

The adult human endolymphatic sac (ES) has been described as a complex network of interconnected tubules. Embryologic examination describes the human ES as a single-lumen, pouch-like structure. Transition from saccular shape to tubules during the entire fetal period has not been previously reported. Tubular ES structure is thought to be unique to humans. Animal investigations describe similar saccular appearance, but without tubules in mature sacs. The authors examined 45 human fetal temporal bones to trace ES development and reviewed six types of animal sacs. Results in humans reveal tubular structure as early as 26 weeks' gestation. Maturation variably occurred in the fetal period and postnatally. For the first time, the tubular system is noted in the animal, the rhesus monkey. These findings suggest that the tubular system may represent more advanced specialized function.

Cochlear implantation in common cavity malformations using a transmastoid labyrinthotomy approach

The transmastoid facial recess approach has become the standard technique for cochlear implantation. Although this approach has been used for implantation in patients with common cavity deformities, it is not without increased risk to the facial nerve. Using a direct approach to the common cavity that circumvents the facial recess, we have successfully implanted four patients with common cavity deformities. An aberrant facial nerve in one patient would have precluded placement of the electrode array using standard cochlear implant techniques. As demonstrated in these four patients, the direct approach to the common cavity is an effective approach for placement of the electrode array, minimizes risk to the facial nerve, and may decrease the likelihood of postoperative cerebrospinal fluid leaks. Intraoperative video footage demonstrates the feasibility and facility of this approach in patients with common cavity deformities.

Marrow-mesenchyme connections in the fetal and newborn tympanum. A new entity

Examinations of 41 human fetal, 8 infant, and 8 juvenile temporal bones prepared for light microscopic evaluation revealed direct connections between the hematopoietic bone marrow and the unresolved mesenchyme in the middle ear. The connections first appeared at 15 weeks of gestation and became bridged by fibrous tissue, in most cases, by the postpartum age of 10 months. Between 16 and 18 months after birth, the marrow-mesenchyme connections gradually disappeared. The areas in which the connections were most numerous were the anterior epitympanum, the sinus tympani medial to the stapedius muscle, and transitory bone that occupies the area that will become the aditus of the antrum. Immunohistochemical staining demonstrated the existence of mature leukocytes in these connections. These connections may help protect the middle ear against bacterial invasion during the postnatal period.

Effect of adult-onset deafness on the human central auditory system

Degenerative change in the central auditory system was assessed in seven subjects with profound bilateral adult-onset deafness. The degree of transneuronal atrophy was determined by measuring cell size at three levels of the brain stem auditory pathway (anteroventral cochlear nucleus, medial superior olivary nucleus, and inferior colliculus). Within subjects, the relative degree of cell shrinkage was similar across all levels of the central pathway. Across subjects, the best neuronal preservation was seen in a case of viral labyrinthitis with 1 year of bilateral dearness and a near-normal population of cochlear ganglion cells. Reduction in cell size was greatest in cases of bacterial labyrinthitis or Scheibe degeneration with reduced populations of ganglion cells and longer periods of deafness. At the level of the cochlear nucleus, there was no consistent difference in cell size between the side stimulated by a functioning prosthetic device and the nonstimulated side.

A five-generation family with late-onset progressive hereditary hearing impairment due to cochleosaccular degeneration

Cochleosaccular dysplasia or degeneration (Scheibe degeneration) is considered the most common cause of profound congenital hearing impairment, and accounts for approximately 70% of cases 2 with hereditary deafness. A five-generation family with hereditary hearing impairment associated with cochleosaccular degeneration has recently been identified. The diagnosis of classical Scheibe degeneration was based on histopathological findings in the temporal bones of the proband, a 61-year-old profoundly deaf male. Auditory structures in the brainstem of the proband were also studied. Twenty-two members of the family were contacted for surveys and blood samples. Of these, 6 males and 2 females have hearing impairment. Complete audiological evaluation was done on 12 family members, and prior audiologic records of the proband and affected family members were available for study. Affected family members suffer a mild bilateral high-frequency hearing loss during childhood and adolescence, and progress to moderate-to-profound deafness in the second and third decades of life. The family is suitable for linkage analysis and does not map to previously reported loci harboring autosomal dominant, nonsyndromic hereditary hearing impairment genes. The genetic study of this family will be helpful in identifying the genes which, when mutated, result in Scheibe degeneration.

Mutational spectrum in the neurofibromatosis type 2 gene in sporadic and familial schwannomas

Using a heteroduplex approach and direct sequencing, we have completed the screening of approximately 88% of the neurofibromatosis type 2 (NF2)-coding sequence of DNA extracted from 33 schwannomas from NF2 patients and from 29 patients with sporadic schwannomas. The extensive screening has resulted in the identification of 33 unique mutations. Similarly to other human genes, we have shown that the CpG sites are more highly mutable in the NF2 gene. The frequency, distribution, and types of mutations were shown to differ between the sporadic and familial tumors. The majority of the mutations resulted in protein truncation and were consistent with more severe phenotype, however three missense mutations were identified during this study and were all associated with milder manifestations of the disease.

Facial nerve schwannoma: nerve fibre dissemination

Biopsy of a middle ear mass can lead to facial paralysis when the mass is a facial nerve schwannoma. Immunostaining techniques were used to determine if nerve fibres might be present within the tumour mass. Nerve fibres were found to be widely disseminated throughout the tumour in eight of 23 facial nerve schwannomas. Antibodies to neurofilaments demonstrated single fibres, or small groups of fibres, that are very difficult to see with routine haematoxylin and eosin stains. The presence of fibres throughout some tumours makes biopsy of them likely to result in facial dysfunction.

Temporal bone findings in Alzheimer's disease

Sensorineural hearing loss has been reported in Alzheimer's disease (AD) and a topographically specific pattern of degeneration in the central auditory system has been described. Although peripheral visual and olfactory systems have been extensively studied, there is no report of peripheral auditory system abnormalities in AD patients. Comparison of temporal bones from eight AD patients with those from eight non-AD controls revealed a significant difference in the percentage of remaining hair cells, peripheral processes, and spiral ganglion cells in the basal cochlear turn but no significant differences in the overall percentage between the two groups. Furthermore, special stains (thioflavin S and Bielschowsky's silver impregnation) of temporal bone nervous tissue from AD patients did not show neuritic plaques and neurofibrillary tangles. It is unclear whether the differences between the two groups in the basal portion of the cochlea are due to AD or some other process, such as presbycusis. However, lack of significant degeneration in other parts of the cochlea and absence of neurofibrillary tangles and neuritic plaques in all eight patients may suggest that the peripheral auditory system, unlike the peripheral visual and olfactory systems, is not involved in AD. A larger sample of AD patients is necessary to clarify the peripheral auditory system findings in the present study.

Constituents of the endolymphatic tubules as demonstrated by three-dimensional morphometry

The various constituents of the tubules of the human adult intraosseous endolymphatic sac were stained with lectins and Millon reaction to reveal some of the carbohydrate and protein-containing substances in the endolymph. The amount of each substance was determined by digitizing sequential temporal bone sections. Differing amounts of the various identified substances were found in sacs from patients with Meniere's disease, patients with labyrinthine fibrosis, and controls.