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In the present study, quantitative analysis of the cochlear neurons in the osseous spiral lamina, the modiolus and the internal auditory canal of the same cochlea was performed. Forty-five temporal bones were obtained from 25 patients and prepared by means of microdissection. Ten patients had age-related normal hearing (ARNH) assuming that the 5 children without audiogram had normal hearing. Fifteen patients had sensorineural hearing loss due to various causes. The present study has shown that in young individuals the numbers of cochlear neurons are almost identical at all 3 sites. In patients over 60 years with ARNH, the loss of peripheral nerve processes is always severer than the loss of central nerve processes. This finding suggests that the central processes degenerate at a much slower rate or not at all. Furthermore, 4 different peripheral degeneration patterns were described. The factors responsible for the different degeneration behaviors are still not understood and need further investigation.

Hypothesis: Blockage of the aeration pathways to the attic may cause circumscribed or widespread alterations that are difficult to diagnose clinically. The narrow route via the posterior pouch to Prussak's space is especially vulnerable to obstruction in recurring otitis media., Background: Recent studies of the epitympanic diaphragm and compartments have clarified the anatomy of the attic aeration and drainage pathways and emphasized the role of their patency in the healing process of middle ear infections. In neonatal otitis media, the amniotic fluid cellular content (AFCC) has proved to be a good indicator in outlining the areas where inflammation products concentrate, possibly causing early blockage of ventilation., Methods: Twenty-eight temporal bones from 14 children were studied; 4 of these children had experienced bilateral recurring otitis media. In the latter group, 1 ear was studied by microdissection and the other by serial sectioning., Results: Prussak's space was involved in all 4 pairs of bones and either contained thick mucus, contained secretion in the process of organization, or was obliterated. The tympanic isthmus was fully obstructed in 1, partially blocked in 2, and open in 5 specimens., Conclusions: If a thick mature connective tissue mass develops under the epidermal layer of Shrapnell's membrane during an obliteration process of Prussak's space, the condition may stay stable and benign. Severe retraction of Shrapnell's membrane represents a likely forerunner of a retraction pocket cholesteatoma. Systematic otomicroscopy allows early detection, and cure can be achieved by minor surgery. In some children, despite the treatment of recurring otitis media with ventilation tubes, the attic and mastoid can be extensively involved, necessitating atticomastoidectomy and the creation of new pathways for attic aeration.

The epitympanic compartments and the anatomy of the atticotympanic diaphragm were examined in a pair of serially sectioned temporal bones with secretory otitis media and chronic otitis media, respectively. Findings confirmed reports of 19th century scientists in that Prussak's space has a wide connection to the mesotympanum through the posterior pouch of Tröltsch and may have an additional narrow passage in its roof to the lateral malleal space. The lateral incudomalleal fold regularly separates the upper lateral attic from the lower lateral attic and the mesotympanum. The medial incudal fold as a rule is atrophic already at birth. The anterior tympanic isthmus thus extends from the tensor tympani tendon to the posterior incudal ligament and is the main passage for epitympanic and mastoid aeration. Opening(s) in the tensor fold, when present, are also important. In some ears, the posterior tympanic isthmus may form an auxiliary narrow route for aeration via the incudal fossa. The isthmi may be blocked by middle ear infection, which can lead to chronic mastoid and attic disease. Pathways for cholesteatoma spread in the epitympanum are discussed.

Three ears with otosclerosis were found incidentally in a series of human temporal bones examined to evaluate cochlear sensorineural degeneration. Otosclerosis was identified with microdissection, surface preparation technique and transmission electron microscopy. Vascular abnormalities were present in all ears, and otosclerosis involved the cochlear endosteum extensively, mainly in the scala tympani of the basal turn. In the scala tympani of the lower half of the basal turn, shunts had formed so that venules deviated abruptly from their normal radiating course towards the spiral vein, left the scala and entered into otosclerotic foci. There was a marked loss of radiating venules in areas where otosclerosis affected the endosteum of the scala. In the pair of bones capillaries in the stria vascularis were extremely dilated, the widest being 80 microns in diameter. The third single bone from a patient with Meniere's disease had severe cochleo-saccular hydrops. Ten serially sectioned temporal bones with known otosclerosis were reviewed. Two of the bones, one of which had cochleo-saccular hydrops, displayed vascular shunts in the scala tympani and enormously dilated strial capillaries with a maximum diameter of 139 microns.

Light and electromicroscopic investigations of Reissner's membrane were undertaken on 10 cochleae from 6 patients with normal hearing for their age. The membrane consisted of two layers, an epithelium and a mesothelium separated by a basement membrane. The mesothelium was formed by a single thin layer which was intermittently discontinuous. The melanocytes were localized on the mesothelial side of the basement membrane. Their numbers was 2-4 times greater in the upper half of the basal turn and in the middle turn than elsewhere. The epithelium was much thicker and had more irregular features than the mesothelium. It was composed of two types of epithelial cells, flat and rounded. The flat cells were more regular in shape than the rounded cells and they were mainly distributed in the middle and apical turns. Judging from their structure they were in a resting state. The rounded cells covered a smaller area than the flat ones and had numerous microvilli. They assumed three different shapes, cuboidal, spindle-form and spherical and were arranged in four different patterns, namely bands, strands, whorls and clusters. The rounded cells were the most active according to the composition of the cytoplasm and dominated the cell population in the hook and the lower half of the basal turn where the age-related sensorineural degeneration is most apparent.

Morphological features of Reissner's membrane were investigated in 6 patients with age-related normal hearing (ARNH) and in 4 with sensorineural hearing loss (SNHL) stemming from various causes. The membrane consisted of an epithelium, a basement membrane and a mesothelium with melanocytes. There were two major forms of epithelial cells: flat and rounded. In all specimens, the rounded cells formed whorls, clusters, strands and bands. The bands were wider and the whorls larger in the basal turn and decreased gradually in size toward the apex. The number of melanocytes was 2-4 times higher in both the upper half of the basal turn and the lower half of the middle turn than in the rest of the turns. In specimens from patients with SNHL, whorls and clusters were both more numerous and larger, and the number of melanocytes was higher in the upper half of the middle turn and in the apical turn than that in the ARNH group. Ultrastructural examination of epithelial and mesothelial cells as well as of melanocytes showed more pronounced cellular degeneration in patients with SNHL than in those with ARNH. A possible correlation between structural alterations of Reissner's membrane and sensorineural degeneration is discussed.

Fiber diameters were analyzed in the meatal segment of the cochlear nerve from 7 temporal bones obtained from 7 patients. Two patients had normal hearing for their age. Two had sustained noise exposure and one had presbyacusis of predominantly neural type. The cochleae displayed characteristic degeneration patterns. The other two manifested hearing loss of unspecified type. The fiber diameters ranged from 0.5 to 11 microns. The diameter distribution was unimodal in all seven nerves. The means of the diameters ranged from 4.2 to 5.5 microns. They were significantly different between patients with age-related normal hearing on the one hand and patients with noise induced hearing loss and neural presbyacusis on the other. The findings are discussed in relation to changes in nerve conduction speed and hearing loss; a possible correlation between the fiber diameter distribution and the tonotopical arrangement of the cochlea is suggested.

A multicentre study of the inner ears of an 88-year-old patient with vertiginous spells and severe hearing loss in the left ear was performed, employing regular and block surface preparations, light and electron microscopy with qualitative and quantitative evaluation of the cochlear and vestibular nerves. There was severe hydrops of the left cochlea and saccule. Reissner's membrane extended into the vestibule and herniated into the perilymphatic space of the non-ampullated end of the horizontal canal. Furthermore, the short canal connecting the posterior ampulla with the utricle had a small, exceedingly thin balloon-like expansion. Only slight hydrops limited to the cochlea was found in the right ear. Sensorineural degeneration was much more pronounced in the left cochlea than in the right. The number of cochlear and vestibular nerve fibres was greatly reduced in the left ear where more fibres with degenerative changes were present. In both specimens the number of myelinated nerve fibres in osseous spiral lamina was smaller than that in the cochlear nerve in the internal auditory canal. Changes occurred in the endolymphatic sacs but were considered non-specific. In this case severe, apparently progressive hydrops and sensorineural degeneration, characteristic of Menière's disease, were associated with atypical onset of clinical symptoms at a late age.

The suboccipital fossa approach to the fundus of the internal auditory canal (IAC) at acoustic neurinoma surgery was investigated in 32 temporal bones. A microdissection was done under the operating microscope in a specially constructed holder so that the surgeon's exposure and angles of view through the craniotomy were mimicked. It was possible to obtain an unobstructed view of the transverse crest and the vestibular nerves in all specimens without the bony labyrinth being opened in the process. A prerequisite was that, as the posterior wall of the IAC was removed, drilling did not extend lateral to a line running through the midpoint of the craniotomy to the transverse crest. The distances of major structures from the posterior and superior pyramid surface were measured, using a special impression technique that made it possible to measure the thickness of the bony layer removed.

The sensory epithelia from the membranous labyrinths of 4 patients were examined by transmission electron microscopy. The distribution ratio of type 1 to type 2 cells was recorded, compared for each sensory area and correlated with age. An ultrastructural assessment confirmed generalized patterns consistent with autolytic and preparation artefact, viz. calyceal dilatation, cytoplasmic protrusions and some sensory hair loss. More specific features, i.e. lipofuscin accumulation, membrane-bound inclusions and neural degeneration were consistent with pre-mortem pathological change. In 2 patients, total nerve fibre counts of 15,766 and 19,741 were obtained. Total fibre counts correlated with the sensory cell density of the innervated areas. Differential counts of the superior and inferior vestibular nerves suggested that there was a reduced number of fibres in the superior division of both patients, in comparison with established normative data. Morphometric analysis of the constituent fibre diameters revealed a skewed distribution with a modal value of 6 microns for both patients.

Cochlear sensory and neural degeneration was examined in nine pairs of human temporal bones fixed by perilymphatic perfusion, using phase-contrast and electron microscopy. Four pairs, three from females, had only slight sensorineural degeneration, limited to the very basal end of the cochlea. A predominantly neural degeneration was identified in a 54-year-old male. The process was bilateral, asymmetrical, uneven, and involved the entire length of the cochlea with several circumscribed areas of severe nerve degeneration. One case had mild, diffuse sensorineural degeneration in the lower half of the basal turn characteristic of presbyacusis. The other three pairs, all from males, revealed sensorineural degeneration patterns associated with noise injury and were remarkably similar to or almost identical with cochleas described previously. There was a good correlation between the presence of supporting cells and the survival of nerve fibres in the osseous spiral lamina in the corresponding area. In one cochlea, however, the degeneration of only inner hair cells in a small area was associated with complete nerve degeneration in the corresponding sector of the spiral lamina. Giant cilia were frequently seen in the apical turn.

The myelinated radial fibres in the osseous spiral lamina and the myelinated fibres in the cochlear nerve in the internal auditory canal as well as the sensory cells were counted in cochleae from 15 dissected temporal bones from 8 patients. Light microscopy was carried out on semithin sections of epoxy resin embedded tissue. Audiometry had been performed within 6 months prior to death. Three patients had normal hearing for their age group, 2 had slight presbyacusis and the remaining 3 had sustained noise injury. All specimens clearly had fewer fibres in the spiral lamina than in the internal auditory canal. The cochleae from patients with normal hearing for their age group had a difference in the nerve fibre counts of up to 34%. A case of sensorineural presbyacusis showed 31%, and a case of neural presbyacusis, 47% difference. The greatest difference was found in a case of acoustic trauma, the range in this group being between 25% and 55%. The lower the number of fibres in the spiral lamina, the greater was the difference in all but two specimens. A slow retrograde degeneration, i.e. beginning in the peripheral process of the cochlear nerve, could be an explanation for these findings.

The temporal bones from a 58-year-old white woman who had had hereditary congenital deafness were examined with the techniques of microdissection and surface preparations followed by sectioning of the modiolus. There was bilateral, almost total sensorineural degeneration, which also involved the saccule. The degeneration of the distal processes of the cochlear neurons in the osseous spiral lamina was almost complete, whereas numerous ganglion cells and proximal processes remained in the modiolus and the internal auditory canal. Severe cochleo-saccular hydrops was present in the left ear with Reissner's membrane bulging into the horizontal canal. X-ray diffraction and electron probe analysis were used to study the abnormal crystalline deposits in both ears. On the left side the saccular otoconia were composed of calcite, but the utricular macula was covered by a crust of apatite spherulites. More apatite occurred around the maculae and in the scala media. The cupulae were composed of apatite and octacalcium phosphate. On the right side the utricular otoconia were of normal calcite, but there was a deposit of apatite on the macula sacculi. The upper part of the scala media was completely filled by a deposit of apatite and octacalcium phosphate.

Four variations and degrees of severity of the Mondini malformation were found in the temporal bones from two neonates, one with congenital heart disease and the other with trisomy D, and from one teenager with leukemia: 1) short cochlea and normal vestibular organs; 2) short cochlea and persistent horizontal canal anlage; 3) markedly shortened cochlea with no modiolus, wide internal auditory meatus, and persistent horizontal canal anlage; 4) same as variation 3, but with persistent anlagen in all semicircular canals. Variations 3 and 4 were from the case of trisomy D, in which the left cochlea had a normal hair cell population but few nerve fibers, and the intraganglionic spiral bundle was displaced from Rosenthal's canal to the osseous spiral lamina. The right ear had no cochlear nerve fibers; the organ of Corti was present, but hair cells were unusually small. In the case of trisomy D, both ears showed subtotal loss of vestibular nerve fibers. Although the rudimentary cristae of the right ear had numerous hair cells, the macular hair cells were fewer and malformed. No hydrops was present.

The death in 1976 of a patient who had a multiple-electrode cochlear implant in one cochlea and a single-electrode cochlear implant in the other provided a unique opportunity for both clinical and histological study of the effects of such implants in a human an subject. The patient was 68 years old at the time of his death. In 1969, at the age of 61, and after 11 years of profound deafness, apparently as a result of lues, the patient was implanted on the left side with a hard-wired 5-wire multiple-electrode cochlear implant. Five years later, his right side was implanted with a single-electrode induction coil cochlear implant. Audiological and psychoacoustic studies were performed by a number of investigators. The results are reviewed. Following the patient's death, his temporal bones were obtained and examined using microdissection techniques followed by serial sectioning. The histological findings are described.

Old World monkeys were exposed to octaveband noise from 0.5 to 8 kHz at 120 dB SPL, 8 hours daily for 20 days. Restricted permanent threshold shifts and localized loss of outer hair cells were produced, which were reasonably well correlated with the exposure frequencies. There was also a loss of both inner and outer hair cells at the extreme basal end of Corti's organ, regardless of the exposure frequency. Implications for human inner ear pathology are discussed.

A 57-year-old patient became totally deaf two days after receiving excessive doses of the aminoglycosidic antibiotic lividomycin parenterally for 14 days; she died four and a half months later. Her temporal bones were examined by microdissection, surface preparation, and serial sectioning of the modiolus. Loss of inner and outer cochlear hair cells was virtually complete. Refractile concretions were scattered along the atrophic stria vascularis, especially in the middle turn. The distal half of the radial cochlear nerve fibers in the osseous spiral lamina had degenerated, but closer to the modiolus they appeared to be intact. The spiral ganglion in the basal turn showed partial loss of neurons. Scanning electron microscopy revealed hair cell loss from the vestibular end-organs, more severe in the ampullar cristae than in the utricular macula. The dark cells of the utricular wall appeared to be altered.

Scanning electron microscopy, electron microprobe analysis, and x-ray powder diffraction were used to study temporal bone specimens obtained at autopsy from an infant with Potter syndrome and from a second trimester fetus, which was the product of an elective abortion. The mothers of both the infant and fetus were juvenile-onset rheumatoid arthritis patients who took prostaglandin inhibitors during pregnancy. The infant's external ears were low set and the left ear canal was stenotic. The vestibular maculae on the left were covered by aberrant otoconia composed of vaterite. In the right inner ear, otoconia were entirely absent, although the gelatinous otoconial membranes were intact. Only the left saccule and right utricle from the fetus were studied; both contained vaterite crystals similar to those in the infant. In addition, apatite was present in the fetal utricle, apparently lying on the macula beneath the vaterite otoconia.

Microdissection and scanning electron microscopy were used to study temporal bone specimens from a newborn infant with Potter's syndrome. The 34-year-old mother of the infant had juvenile-onset rheumatoid arthritis and she took prostaglandin inhibitors (aspirin, indomethacin, and Clinoril) during pregnancy. Autopsy findings included bilateral renal dysgenesis, pulmonary hypoplasia, abnormal facies with low-set ears, and bilateral cataracts. The infant's left external ear canal was stenotic and the left tympanic anulus was narrowed. Otherwise, both middle ears, as well as the sensory structures of the cochleae and semicircular canals, were normal. The saccular and utricular muculae on the right were entirely devoid of otoconia, although they were covered by gelatinous otoconial membranes which appeared normal. On the left, the maculae were covered by thin layers of flat, lenticular crystals 2 to 10 mu in diameter. X-ray powder diffraction analysis showed these aberrant otoconia to be composed of calcium carbonate in the form of vaterite. No abnormalities of the neuroepithelia or macular nerve supply were found in either ear.

Temporal bones from five patients with hearing loss as a result of aminoglycoside treatment were examined by the method of microdissection and surface preparations, followed by celloidin embedding and serial sectioning of the modiolus. Three patients had received the newer antibiotics, gentamicin, tobramycin, and amikacin; the other two neomycin. In the cochleas from two patients of the first group there was only a small loss of hair cells, restricted to the lower end of the basal turn. The third, who had been treated with several antibiotics over a longer period of time, showed more extensive but strikingly asymmetrical patterns of degeneration in the two ears. This patient, as well as the fourth, who had received neomycin during peritoneal lavage, had numerous patchy areas of complete disappearance of Corti's organ in the basal turn, with incipient degeneration of the distal ends of the nerve fibers in adjacent portions of the osseous spiral lamina. The fifth patient, who had become deaf after prolonged treatment with neomycin by mouth, showed a complete loss of cochlear hair cells. Nerve fibers were present only in the middle and upper turns, where supporting cells remained. Midmodiolar sections showed a proportionately much greater loss of the distal than of the proximal processes of the cells of the spiral ganglion. These findings underscore once again the special hazard for the inner ear that is associated with the clinical use of neomycin, regardless of the route of administration.

The temporal bones from a 55-year-old woman with deafness and dizzy spells caused by a right-sided acoustic neurinoma were examined by the techniques of microdissection, surface preparations, and celloidin sections. Sensorineural degeneration was present in the basal end of the right cochlea but was not severe enough to explain the deafness. The compression of the cochlear nerve by the tumor was postulated to have caused deafness by injury to neurons adjacent and central to the tumor. There was profound degeneration of the vestibular nerve and sensory cells. A gelatinous material occluded the scala vestibuli, and the vestibular fluid spaces contained an amorphous proteinaceous substance. Fewer erythrocytes were seen in the vessels of the right cochlea, but there was no atrophy of capillaries to indicate long-term reduction of circulation. Vasculoneogenesis of venous vessels had occurred in the scala tympani, probably as a result of venous stasis.

Damage to the neuro-epithelium caused by the vestibulotoxic drugs has been well described in previous reports; however, little is known about the effect of such drugs on the otoconia. In this investigation, streptomycin sulfate was found to create a circumscribed defect in the crystalline layer of the otoconial membrane in the utricle of the guinea pig. The defect was secondary to a sharply outlined lesion of the neuroepithelium which corresponded in size and location to the otoconial defect. Many of the otoconia along the margin of the defect showed signs of degeneration and appeared similar to those observed in the saccule of man during aging. In advanced stages of decay, the otoconia were reduced to hollow shells consisting of longitudinal interconnecting strands. All the epithelial lesions occurred with remarkable consistency in the same region of the macula utriculi at the posterior end of the striola.

Abnormal mineral deposits from the membranous labyrinths of deaf Dalmatian puppies were examined microscopically. Most such deposits were located on the saccular otoconial membrane and were associated with collapse of the saccule and of Reissner's membrane. In both ears of one pup, crystals resembling otoconia were found on the surface of the stria vascularis. In two others, grossly abnormal crystals were seen on the utricular otoconial membrane, and in one of these crystals were also attached to the cupula of the left horizontal canal. In four animals the tectorial membrane was calcified. Most deposits consisted of apatite spherulites, but large multiple crystals (probably of calcite) were occasionally present. Some of the abnormal mineral deposits in the Dalmatian closely resemble those found in man, and they may originate in the same way.

A small intracochlear neurinoma was found in the temporal bone of a 54-year-old man who had no history of hearing loss or dizziness. The tumor was small, confined to the scala tympani, and did not visibly alter the tissues around it. The neurinoma was derived from the distal processes of the cochlear neuron. Intralabyrinthine tumors can cause auditory and vestibular symptoms and are difficult to diagnose.

The inner ears obtained from an infant who died of severe congenital cytomegalovirus infection were examined using virological and morphological methods. The techniques of microdissection and surface preparations, immunofluorescent microscopy, and transmission and scanning electron microscopy were employed. Cytomegalovirus was isolated from the perilymph. Injury to the cochlea was minor and was confined to the first half of the basal turn. There were signs of a severe labyrinthitis of the vestibular endolymphatic system. Vestibular organs, especially the saccule and utricle, showed severe damage, with collapse of the saccular membranous wall. Inclusion-bearing cells containing cytomegalovirus antigen, as shown by immunofluorescent staining, and cytomegalovirus virions, as observed by electron microscopy, were found on the endolymphatic surface of the membranous walls, mainly in the saccule and utricle. In the utricle, the infected cells appeared to be concentrated in the regions where the so-called dark cells were located. These dark cells are similar to the proximal tubule cells in the kidney, another common target for cytomegalovirus infection.

The histopathological changes in a pair of temporal bones from a 69-year-old woman who had secretory otitis media in the left ear and chronic middle ear infection in the right ear are described. Tympanostomy tubes had been placed in her left ear nine times. The perforation at the grommet showed no ingrowth of squamous epithelium; the fine structure of the tympanic membrane was normal. There were a few mucus strands present in the middle ear, which was lined with a one- to three-cell layer epithelium, where only a few secretory cells were found. In the right ear the thick tympanic membrane showed papillary projections of the squamous epithelium extending from the outer epidermal layer deep into the stroma and close to the collagenous layer of lamina propria. A large marginal perforation was present in the posterior quadrant, but there was no ingrowth of squamous epithelium from the canal into the middle ear. From the anterior margin, a concave veil-like sheet of squamous epithelium had grown onto the incus, chorda tympani and the stapes head. Numerous finger-like projections extended from the margin of this epithelium to the stapedial footplate and the epitympanum. The mucous membrane of the bony portion of the Eustachian tube in both ears was normal to the cartilage level, and the defective ventilation was in all likelihood caused by a dysfunction at the pharyngeal end of the Eustachian tube.

Neuroepithelial suprastructures in abnormal human inner ears were studied by light microscopy, scanning electron microscopy, and x-ray diffraction. The most common abnormality was calcification, which selectively affected the gelatinous membranes (otoconial, cupular, and tectorial) and the secretory tissues (stria vascularis and utricular dark cells). The structures most frequently affected were the otoconial membranes. The minerals involved were apatite, octacalcium phosphate, and vaterite, replacing the normal layer of calcium carbonate in the form of calcite crystals. The first two of these substances were sometimes mixed with calcite. In the saccule such abnormal otoconial deposits were usually associated with a collapsed saccular wall. Formation of abnormal otoconia is characterized as primary (no pre-existing normal calcite otoconia) or secondary (formed after the destruction of normal otoconia). Such deposits probably depend upon an abnormal composition of the endolymph, especially upon an elevated concentration of phosphate ions. It is inferred that a normal endolymphatic microhomeostasis is necessary to maintain the functional state of the neuroepithelial suprastructures.

In 24 temporal bones from patients with otosclerosis prepared by the method of microdissection and surface preparations, otosclerotic foci could be clearly seen during removal of the otic capsule. The state of activity of each focus was estimated on the basis of its consistency and vascularity. Small anterior foci constituted the most common form of involvement of the otic capsule. All were judged to be inactive, and none of them appeared to have caused obvious sensorineural degeneration. No cases of "pure cochlear otosclerosis" were seen. Sensorineural degeneration was associated with large anterior foci which reached the upper basal turn. One specimen displayed a circumscribed sensorineural degeneration in the upper basal turn, with an almost exact correspondence between the location and extent of the cochlear lesion and the site of invasion by the otosclerotic process in the bone and endosteum bordering on scala media and scala tympani. It is postulated that a toxic factor had diffused from the focus and acted directly on the organ of Corti. When multiple foci were present they were usually poorly defined. The otosclerotic process involved the round window, with new lamellar bone formation in the scala tympant of the lower half of the basal turn. The most extensive sensorineural degeneration in the entire material was seen in this group. One specimen also had severe cochlear hydrops. In three specimens large shunts were observed to connect the otosclerotic foci with the cochlear vasculature, which was severely dilated. Where otosclerosis involved the endosteum of the scala tympani, loss of vessels was observed. One specimum with extensive active capsular otosclerosis had severe sensorineural degeneration of the vestibular system. Vestibular pathology in fenestrated ears is also described. In a specimen from a patient with no caloric reaction, numerous hair cells were present in the macular organs.

Various forms of sensorineural degeneration patterns related to noise exposure are illustrated in six pairs of temporal bones selected from a group of 33 male patients with histories of noise exposure. For the entire group the commonest form of lesion, associated with a 4-kHz dip in the audiogram, was a relatively diffuse degeneration in the second quadrant of the basal turn, in the 9-13 mm area. An advanced form of this lesion had a wide gap of more or less complete sensorineural degeneration affecting the entire second quadrant and displaying various degrees of extension toward the apex and base. The pattern associated with an "abrupt high-tone loss," with more or less complete hair cell and nerve degeneration in both the second and first quadrants and extending to the basal end of the cochlea, was rare. In one case this pattern appeared to have evolved from the first type of lesion as the remaining nerve fibers in the first quadrant had degenerated. The protective effect of the acoustic shadow of the head for the right ear, in shooting from the right shoulder, is demonstrated for the higher frequencies. Two almost identical cases of sharply-circumscribed single areas of degeneration in the first quadrant and one case with two such areas represent the third type of lesion. In one of these cases there was a history of firearm usage. It is postulated that this type of lesion is caused by impulse noise. In most of the material the degeneration pattern differed markedly from the diffuse degeneration seen with presbycusis. Degeneration patterns with knife-sharp transitions between completely degenerated and apparently undamaged areas appear to be characteristic of noise-induced injuries.

Specimens of human otoconia obtained from autopsy material and representing various stages from fetal to advanced old age, were studied by microdissection, scanning electron microscopy, electron microprobe analysis, and x-ray powder diffraction. The typical adult otoconial configuration is a cylindrical, finely serrated body with pointed ends; crystallographically, it corresponds to a single crystal of calcite. Other, less numerous typed include jointed otoconia, pure rhombohedrons and multifaceted, presumably immature forms. Many otoconia achieve the adult configuration during fetal development. The multifaceted otoconia are most numerous, and the rhombohedrons proliferate, during childhon in the young adult, but saccular otoconia are the larger. In middle and advanced age the otoconia decrease in number, especially in the saccule. Saccular otoconia degenerate progressively in a posteroanterior direction across the macula; they assume a specific, fibours, hollowed-out appearance, which is not duplicated by either chemical etching or autolysis. Neogenesis and growth of otoconia appear to occur postnatally, with different characteristic growth potentials for those of the saccule and the utricle. Age-related saccular otoconial degeneration appears to involve the organic material, which disappears either before or simultaneously with the mineral substance.

The specimens were obtained from a 63-year-old white male with acquired lues. The patient experienced sudden profound deafness on the left side 15 years prior to death, and a similar loss on the right side 3 years later. By the time of death he had carried a single induction coil in the right ear for 3 years and multiple (5) hardwire electrodes in the left ear for 8 years. A complete micro-dissection or "mini-autopsy" of the specimens was performed, and the modiolus was sectioned. Photomicrographs of the dissections will be shown. In the right ear supporting elements and numerous nerve fibers were present in the apical turn. The electrode on this side was apparently tolerated well; scala tympani was normal in shape and appearance. On the left side no nerve fibers were found in the osseous spiral lamina and there was extensive new bone formation in scala tympani. It is difficult to determine if or to what extent the implants were responsible for the severe sensorineural degeneration observed in both specimens. There was severe scarring and ossification of the posterior ampulla in both ears, in all likelihood resulting from the surgery. Some aspects of surgical techniques will be discussed in view of the histopathological findings.

The organization and the otologic research in the Otorhinolaryngology Department of the University of Helsinki are described. The department has 4 surgical wards, each with 22 beds, and a new surgical wing with 6 full-sized operating rooms. The ear research is centered on middle ear histopathology and immunology, focusing especially on secretory and chronic otitis media. There is an audiological and vestibular unit, the latter is expanding rapidly. Acoustic neuroma surgery is performed as team work with a neurosurgeon. The department takes part in a cochlear implant and Audiant prosthesis program.

Cochlear hair cell counts from individuals who had clinically normal hearing prior to their death have been plotted for various age bands as a function of the number of hair cells per millimetre against their position in the cochlea. Position has been expressed as the distance of that observation of hair cell density from the base of the cochlea, divided by the total length of the cochlea, thereby giving a proportional representation of the cochlea in the range of 0.0 to 1.0 with 20 subdivisions of 0.05. There is an age-related decrease in the number of hair cells in the normal population, and this is more marked for the outer hair cells.

Otoconial membranes from a large number of normal albino and pigmented guinea pigs were examined by light microscopy. In more than 20% of the animals, microdissection revealed that the crystalline layer of the otoconial membrane was incomplete, leaving large areas of the underlying gelatinous layer uncovered by crystals. These defects were bilateral, more or less symmetrical, and invariably more extensive in the saccule than in the utricle. In two animals, huge single conglomerates of crystals were found on both the saccular and utricular maculae. None of the animals displayed abnormal behavior or posture and no obvious cause for the otoconial defects was found. The presence of a hereditary congenital condition is postulated. The high incidence of otoconial defects in guinea pigs makes them poorly suited for most investigations of experimentally induced pathology. Therefore, previous reports of otoconial pathology in guinea pigs should be viewed in the light of these findings.

Eight Old World monkeys were exposed 8 h daily for 20 days to octave-band noise having center frequencies from 0.5--8 kHz at levels of 117--120 dB SPL. Two additional animals received exposures to wide-band, 120-dB SPL noise on the same schedule, and one animal was exposed to the 2-kHz octave band for 40 h continuously. Behavioral audiograms were measured throughout exposure and during a 1-month recovery period. Following recovery, the animals were sacrificed and their ears examined histologically. Monaural audiograms are presented showing initial and final TTS and PTS measured at the end of the recovery period. These are compared with complete cytocochleograms for each ear. Hair cell loss was generally restricted to the outer rows, and was reasonably well correlated with pattern of hearing loss. Some cell loss, including inner hair cells, was found in the extreme basal turn, usually without associated high-frequency hearing loss. The relationships between exposure frequency, hearing loss, and locus of cochlear pathology are discussed, as are changes in TTS during exposure.

45CaCl2 was injected into gerbils in single or multiple doses, and the resulting radioactivity in serum, otoconial CaCO3, bone samples, and selected labyrinthine epithelium was determined by liquid scintillation spectrometry. Incorporation into both utricular and saccular otoconia occurred at the rate of 0.06-0.07 nmole Ca++ per day, corresponding to a fractional rate of uptake of 0.1%. The retention of radioactivity had a half-life of approximately 11 days. The rate of incorporation of calcium for the middle ear ossicles was 5-7 times that for otoconia and was similar to that for otic capsule and skeletal bone. The level of 45Ca++ was higher in the pigmented regions of the utricular membranous wall than in the non-pigmented areas of the utricular and ampullary wall and in the stria vascularis.

The cochleae of four patients with a diagnosis or suspicion of Alport's syndrome were examined by microdissection and surface preparations. Strial atrophy, found in all cases, was most pronounced in the middle and apical turns and mainly involved the inferior margin of the stria. Numerous vacuoles were seen in the spiral ligament behind the atrophic stria. The youngest patient, aged 16 years, who had little or no hearing loss, showed limited hair cell degeneration. The other two patients had severe hearing loss and extensive sensory cell loss of unusual distribution. In the specimens from the second patient, the extent of hair cell loss was fairly even throughout, but the loss of inner hair cells was far more severe than the loss of outer hair cells. In the third case, the loss of outer hair cells was most pronounced in the apical half of the cochlea. All of these specimens had only a mild secondary nerve degeneration. The specimens from the fourth patient were poorly preserved and showed only nerve degeneration.

Ceramic stems, their lateral end capped with a modelled ossicle, or ceramic prostheses manufactured with a cap-shaped head were used as a columella from the stapes footplate to the tympanic membrane or a fascia graft in 41 ears operated on during 1982-1985. Six ears had no membrane perforations and no severe disease of the tympanic mucosa. Twelve ears underwent primary operations for cholesteatoma and 23 ears had revision surgery. Good hearing improvement occurred in well-aerated ears while hearing in ears with extensive tympanic disease did not improve after surgery. No tissue reactions to the ceramic prosthesis were observed and no prosthesis was extruded. Ceramic can be regarded as an acceptable alternative to bone for columella grafts used in surgery for chronic middle ear disease when the stapes superstructure is missing.

Large cholesterol cysts were found in revision surgery in six patients with previous ear surgery one to 28 years ago. The cysts mimicked brain herniation in open cavities, filled the mastoid and ear canal in closed cavities, or caused postauricular swelling. Bone around the cysts was soft and granulomatous. Secretory cells were scarce in the epithelial lining of the lumen, but subepithelial glands were frequent. Cholesterol granulomas and hemosiderin-laden macrophages were present inside the wall. The cyst lining and the glands under it showed cytokeratin staining typical for simple and glandular epithelia. Antiprekeratin antibodies showed no decoration of the lining but reacted positively with the meatal skin. These findings prove that respiratory-type epithelium separated from an aerated middle ear does not undergo changes into keratin-forming epithelium.

The influence of neomycin and streptomycin on the calcium metabolism of the otolithic membranes was investigated in the guinea pig. After chronic treatment with either drug, animals were injected intraperitoneally with radioactive calcium. Retention of calcium in the serum was unaffected by drug treatment, as was the incorporation of radioactivity into bone (femur and otic capsule). Both drugs inhibited the calcium uptake into saccular and utricular otolithic membranes by 30 to 40%.

We have studied saccular and utricular otoconia from Shaker-1 and Shaker-2 mice by X-ray diffraction and scanning electron microscopy. In contrast to previous reports, we found that the crystals were composed of calcite rather than polycrystalline hydroxylapatite. These crystals were indistinguishable mineralogically and morphologically from normal mouse otoconia. The reported occurrence of hydroxylapatite otoconia in the Shaker mouse is probably false.

Localized perivascular demyelinization of the peripheral processes of cochlear neurons was observed in surface preparations of the osseous spiral lamina in two neonates, one a premature infant with erythroblastosis fetalis, the other a full-term infant with cyanotic congenital heart disease. In both cases the cause of the demyelinization was unknown. Both infants had severe edema as a result of congestive heart failure and anoxia. The serum bilirubin level in the erythroblastotic child appeared too low to have caused injury to the nerve fibers. The demyelinization was most striking in the lower half of the basal turn. It was observed only in the immediate vicinity of meandering stretches of capillaries as they crossed the nerve fibers. In the premature infant there was hair cell loss throughout the cochlea; in the other there was no hair cell loss, but a malformed labyrinth of the Mondini type.

Temporal bones from four patients with capsular otosclerosis were examined by microdissection. Otoconia and abnormal crystalline deposits were studied by scanning electron microscopy and x-ray analytical methods. One patient showed more or less symmetrical invasion of the basilar membrane and osseous lamina by connective tissue from thickened endosteum adjacent to the larger anterior foci. In one ear sensorineural degeneration was circumscribed; in the other it was extensive and associated with cochleosaccular hydrops. Two other patients were deaf, with severe sensorineural degeneration; one had multiple active foci and evidence of cochleosaccular hydrops. In the fourth patient, who had small anterior foci, no specific inner ear pathology was found related to otosclerosis. In the hydropic labyrinths, apatite was present as abnormal deposits in the cochlear duct and as rigid crusts replacing the otoconia. Apparently these changes had been associated with abnormal labyrinthine fluid dynamics rather than with the otospongiotic process per se.

Normal cochlear function was preserved in a patient after excision of the membranous canal from a huge fistula at revision surgery eight years after the primary procedure. A recurrent cholesteatoma had eroded the entire prominence of the horizontal canal and surrounded its membranous portion. The cholesteatoma, including the membranous canal, was removed in a one-stage procedure. The open ends of the bony canal were sealed with a fascia soaked in fibrin glue. After initial dizziness and severely reduced hearing, the patient quickly recovered, with normal bone conduction and a stable 30-dB hearing level by air conduction. The lumen of the membranous canal was patent, and only the ampullar end was atretic. Presumably, the fistula became separated from fluid spaces by formation of perilymphatic partitions and by collapse of the membranous labyrinth adjacent to the fistula.

The remarkable susceptibility of the inner ear of the patas monkey (Erythrocebus patas) to the ototoxic action of dihydrostreptomycin (DHSM) (and streptomycin (SM)) is well established in this paper and affords a rare example of a species-specific reaction to a restricted class of compounds within the aminoglycoside group of antibiotics. In a series of experiments, behavioral and morphological observations together provided the following profile of DHSM ototoxicity in the patas monkey: Sudden onset of hearing loss beginning after 7-9 weeks of treatment; Substantial, though often partial, hearing impairment beginning at the high frequencies and progressing with or without continued treatment to the low frequencies; In the inner ear, a corresponding and selective loss of nerve fibers and of outer hair cells, relative to inner hair cells, beginning in the base of the cochlea and proceeding toward the apex; Continued and progressive loss of hearing for several months after cessation of drug treatment; and Non-auditory effects in some animals on the kidney and vestibular system. Results from control experiments confirmed this special relationship between the patas monkey and DHSM: Other nonhuman primates (macaques and vervet monkeys) were essentially unaffected by DHSM; The patas showed no equivalent sensitivity to other aminoglycosides such as kanamycin or to other forms of ototraumatic insult such as intense noise.