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At least 1,225 records · Page 68Linked to original sources
PubMed2004

Rapid prototyping of temporal bone for surgical training and medical education.

OBJECTIVE: The skills of ear surgery are best developed by dissecting a temporal bone. However, only a limited number of trainees can be afforded this opportunity because of the scarcity of available bones. The aim of this study was to investigate the validity of a prototype temporal bone model for surgical training and education. MATERIAL AND METHODS: A simulated 3D model of a human temporal bone was made using a selective laser sintering method. The powder layers were laser-fused based on detailed CT data and accumulated to create a 3D structure. Conventional surgical instruments were used to dissect the model under a microscope. RESULTS: The model was as hard as real bone and surface structures were accurately reproduced. The model could be shaved using a surgical drill, burr and suction irrigator in the same way as a real bone. The malleus and incus were reproduced. The semicircular canals and the oval and round window niches were identified. Cavity structures, such as the semicircular canal, vestibule, antrum and air cells, were filled with powder which had to be removed using a pick and suction irrigator during dissection. A magnified model was useful for educating medical students. CONCLUSION: This prototype 3D model made using selective laser sintering serves as a good educational tool for middle ear surgery.

Humans↗
PubMed1983

Cochlear dysfunction in the jerker mouse.

Surface preparations show that the jerker (je/je) mutant mouse has a normal total number of cochlear hair cells when young but that these progressively degenerate with increasing age. However, no gross 8th nerve action potentials or cochlear microphonics could be detected at the round window in 12-20-day-old mutants, although many hair cells still appear to be intact at these ages. Light microscopy of surface preparations is apparently a poor indicator of the functional state of hair cells, at least in genetically determined inner ear defects. The endocochlear potential (EP) was significantly higher in the mutants than in controls during the maturation of the cochlea. During anoxia induced in adults, EP fell to a significantly less negative value in mutants than in control mice. This abnormality in the anoxia potential probably reflects an organ of Corti abnormality.

Age Factors↗
PubMed1992

[Evaluation of compound action potential tuning curves from normal guinea pig cochleas].

Eighteen ears of normal guinea pigs were examined by means of compound action potential tuning curve (AP-TC) with different measure parameters. AP-TC was measured at pure-tone of various frequencies using simultaneous masking procedure by the electrodes on the round window. AP was evoked by filter click (2, 3, 4, 5, 6, 10 kHz) with an intensity 10, 30 and 50 dB above threshold. Masker level producing 30% reduction in AP amplitude was used. The results showed that AP-TC was more sharply as test frequency was elevated. It is corresponded well with the published results. No differences in tuning (i.e., the form of the curves and Q10 dB values) and thresholds were found between two different times for the same animal. In addition, the Q10 dB values of AP-TC were gradually reduced along with the elevate of the test stimuli intensity from 10 to 50 dB above threshold.

Action Potentials↗
PubMed1977

Joint Committee on Aviation Pathology: XVII. Round window tear in aviators.

It is the intent of this paper to draw attention to round window tears with the inherent symptomatology that has, for the first time, been documented in two aircrew members. It is also felt important to emphasize that the condition, regardless of etiology, could be catastrophic to the flying pilot and may be an up-recognized cause of otherwise unexplainable accidents. Not all cases of window tears cause vertigo-but some do. Not all vertigo so caused is prostrating--but some is. Because of the findings in two reported cases, it is postulated that round window membrane tear may be a significant cause of pilot disorientation. It may have been the root cause of peculiar and previously unexplained air crashes. The corollary of this hypothesis is the proposition that, in the future, careful attention be paid to the ears of pilots recovered from what would otherwise appear to be a mysterious accident.

Adult↗
PubMed2001

Distinguishing cochlear pathophysiology in 4-aminopyridine and furosemide treated ears using a nonlinear systems identification technique.

To test the adequacy of physiologic indices derived from a third-order polynomial model quantifying cochlear mechano-electric transduction (MET), 24 Mongolian gerbils were exposed to either 250-mM glucose (control), 150-mM 4-aminopyridine (4-AP), or 30-mM furosemide solutions applied to the round window (RW) membrane. The cochlear microphonic (CM) was recorded from the RW in response to 68- and 88-dB SPL Gaussian noise. A nonlinear systems identification technique (NLID) provided the frequency-domain parameters and physiologic indices of the polynomial model of MET. The control group showed no change in both compound action potential (CAP) thresholds and CM. Exposure to 4-AP and furosemide resulted in a similar elevation in CAP thresholds and a reduction in CM. However, the polynomial model of MET showed different changes. The operating point, slope, and symmetry of the MET function, the polynomial model parameters, and related nonlinear coherences differed between the experimental groups. It is concluded that the NLID technique is sensitive and specific to alterations in the cochlear physiology.

4-Aminopyridine↗
PubMed2000

Acoustic impedances at the oval window, and sound pressure transformation of the middle ear in Norwegian cattle.

In 15 cadaver ears from Norwegian cattle, sound pressure transfer functions have been measured (1) for sound input to the tympanic membrane, (2) for sound input to the oval window with the footplate in place, but with the ossicular chain removed, and (3) for sound input to the oval window with also the footplate removed. The output pressure was measured in an enclosure cemented to the round window. The data allow calculation of equivalent sound pressures at the input positions, as well as the acoustic input impedances at the oval window with intact footplate, Z(sc), and with the footplate removed, Z(c). The difference Z(s)=Z(sc)-Z(c) is the acoustic impedance contribution of the footplate and annular ligament. Z(sc) is mainly determined by the stiffness of the annular ligament at low frequencies, and by the cochlear input impedance Z(c) at higher frequencies. Z(c) is predominately resistive, a minor reactive part at low frequencies is attributed to the stiffness of the round window membrane. Z(s) and Z(c) are equal in magnitude at about 0.4 kHz. Rather close RLC fits have been obtained for all the three impedances, Z(sc), Z(s), and Z(c). The fitted values for the resistive parts of Z(sc) and Z(c) are 62.9 and 58.2 acoustic Gomega, respectively. The relatively small difference, 4.7 Gomega, is attributed to the resistance of the annular ligament. The fitted resistance of Z(s) is somewhat larger, 8.6 Gomega, but is anyway of minor importance relative to the dynamic stiffness of the annular ligament. This stiffness depends on the static pressure difference across the footplate. Each of the averaged Z(sc) corresponds to minimum stiffness. The fitted acoustic compliance is 6.89 x 10(-15) m3/Pa. The acoustic inertance plays a minor role. It is attributed to the mass of the footplate and the co-vibrating liquid in the inner ear, and has a fitted value of 4.7 x 10(5) Pa s2/m3. A sound pressure at the eardrum is equivalent to a larger pressure at the footplate, about 16 dB larger at frequencies below 100 Hz, increasing to about 30 dB at 10 kHz. In the vestibulum at the inner side of the footplate, the sound pressure at 20 Hz is about 20 dB below the equivalent pressure at the outer side. The two pressures approach toward higher frequencies, and above 1 kHz they are nearly equal.

Acoustic Impedance Tests↗
PubMedDate not supplied

The topographic relations of the high jugular fossa to the inner ear. A radioanatomic investigation.

The radioanatomy of high jugular fossae and their topographic relations to the inner ear structures were investigated in 245 unselected temporal bones. One hundred and fifty specimens were submitted to multidirectional and 10 to computed tomography. After careful chemical and fermentative maceration plastic casts were made, using polyester resin and silicone rubber. With the use of vacuum, even minute structures became filled with the casting material. The specimens offered a three-dimensional view of the jugular fossae and surrounding structures. Fifty-eight (24%) of the total 245 specimens had high jugular fossae at a level above the lower border of the round window. Five casts showed a dehiscence of the peripheral portion of the vestibular aqueduct caused by the high jugular fossa. In 2 casts the proximal portion of the cochlear aqueduct was affected. In some casts the posterior semicircular canal, the facial canal, the stapedial muscle and the round window lay so close to the fossa that a dehiscence could not be excluded. In a clinical material of 102 high fossae the radiographic findings were in accordance with the experimental results. High jugular fossae were predominantly found in pyramids with low-grade mastoid bone pneumatization and sparse or no perilabyrinthine air cells.

Adolescent↗
PubMed1965

BACKGROUND AND EVOKED ACTIVITY IN THE AUDITORY PATHWAY: EFFECTS OF NOISE-SHOCK PAIRING.

Unanesthetized cats with electrodes permanently implanted along the auditory pathway were presented first with suistained " white" noise stimuli and then with the same noise paired with subcutaneous electric shocks. Pairing noise with shock decreased both background and noise-evoked activity inthe inferior colliculus, and, in some cats, also in the cochlear nucleus, trapezoid body, and at the round window. No changes occurred in medial geniculate or auditory cortex recordings. The effects in the inferior colliculusdo not depend on changes in the degree of arousal of the animal, on change in the medullary auditory areas, or on the actions of the middle-ear muscle.

Animals↗
PubMed1996

[Experimental research on delayed responses in cochlear microphonics records in guinea pigs].

Clinical application of evoked otoacoustic emissions (EOAEs) is expected to serve as an objective indicator of inner ear function. Delayed extra waves (delayed responses) from human cochlear microphonics (CMs) have been observed and they appear to be electrical correlates of EOAEs. Delayed responses must be examined for their relation to EOAEs in animal experiments before clinical application. The present experiment was performed to elucidate the relationship between delayed responses and the EOAEs in guinea pigs. Delayed responses to weak sound stimuli were recorded from the round window and from the scala media. The second waves, which corresponded to CMs, were compared with the fourth or fifth waves. The input-output curves of the fifth waves saturated earlier and crossed the curves of the second waves. Both the second wave and the fifth wave decreased in anoxia, but their time course of amplitude changes in anoxia were different. EOAEs peaked between 2.5 kHz and 3.5 kHz in the frequency distribution. The EOAEs also were anoxia-sensitive, corresponding to changes in the CMs and the delayed responses in the time course of anoxia. The results of the present experiment demonstrate that the delayed responses were electrical correlates of the EOAEs. EOAEs are believed to represent energy leaks to the external and middle ear from intracochlear micromechanics linked to retrograde transduction mechanism of the outer hair cells. This was supported by the relationship between the delayed responses from the CMs and the EOAEs. The EOAEs and delayed responses may serve as tools for application in clinical testing as acoustical and electrical indicators of intracochlear micromechanical function.

Animals↗
PubMed2001

L-n-acetyl-cysteine protection against cisplatin-induced auditory neuronal and hair cell toxicity.

OBJECTIVES: The aim of this study is to determine the efficacy of L-N-acetyl-cysteine (L-NAC) as a protectant for inner ear auditory sensory cells against the toxic effects of cisplatin. STUDY DESIGN: Prospective laboratory study of the otoprotective effect of L-NAC on auditory neurons and hair cells in vitro. METHODS: The study has two arms. The first arm evaluated the neuroprotective effect of L-NAC on early postpartum auditory ganglion cell cultures. Two culture media were used. The two media differed in that one of them was enhanced by the addition of neurotrophins (neurotrophin type 3 and brain-derived neurotrophic factor) and a growth factor (transforming growth factor-beta1). Then the survival of cisplatin-treated auditory neurons was studied before and after pretreatment with protective levels of L-NAC. The second arm of the study evaluated the effect of L-NAC on cisplatin damage initiated to auditory hair cells. Early-postpartum organ of Corti explants were grown in culture. Their rate of survival was studied after exposure to toxic levels of cisplatin. Then, survival of cisplatin-damaged hair cells was studied after they were pretreated with L-NAC. RESULTS: Pretreatment of cultures with L-NAC protected both auditory neurons and hair cells from the effects of exposure to toxic levels of cisplatin. This observed otoprotective effect was dose dependent. CONCLUSIONS: Our in vitro studies have demonstrated that L-NAC protected both auditory neurons and hair cells from the toxic effects of cisplatin. Because it protects both of these inner ear structures, L-NAC may be potentially useful in protecting hearing, in general, from cisplatin-induced damage. In addition, L-NAC has low systemic and mucosal toxicity. It also has a low molecular weight that may allow it to readily cross the round window membrane. All these characteristics make it potentially suitable for transtympanic application for the prevention of the ototoxicity of cisplatin in vivo.

Acetylcysteine↗
PubMed1990

[Ultrastructural changes of the cochlea in guinea pigs with acute bacterial otitis media].

Acute bacterial otitis media was induced in guinea pigs with H. influenzae to investigate the ultrastructural changes of the organ of Corti. The results showed that the stereocilia in the organ of Corti adjacent to the round window was disoriented and partially disappeared, there was an increase in the number of lysosomes and marked aggregation of smooth endoplasmic reticula, the surface of the supporting cells was damaged and broken. The most prominent damages were observed on specimens 7 days following the middle ear inoculation with H. influenzae. The damages to the supporting cells were repaired 21 days after the inoculation though the damaged stereocilia did not show any sign of recovery.

Animals↗
PubMed1996

Erbium laser in middle ear surgery: in vitro and in vivo animal study.

Cadaveric human temporal bones, cadaveric rabbits, and live rats were used to demonstrate the utility and safety of the erbium:yttrium-scandium-gallium-garnet (Er:YSGG) laser for otologic applications. The shallow penetration in water of this wave-length and its ability to ablate bony tissue with minimal collateral thermal effects spare underlying and adjacent structures and make it appealing for stapedotomy. The authors were able to satisfactorily perform small fenestra stapedotomy, atticotomy facial nerve decompression, and mastoidectomy. Temperature measurements from the round window area during Er:YSGG stapedotomy recorded an elevation of less than 2 degrees C, which is well within acceptable limits. An acoustic shock produced at the impact site is the major disadvantage and requires further in vivo investigation of the transient and sustained deleterious effects away from the application site. This work supports further investigation into potential applications of the Er:YSGG laser in otology.

Animals↗
PubMed2003

[Temporal bone study of residual mastoid inflammation in ears with normally appearing tympanic membrane].

We examined 395 temporal bones with an intact tympanic membrane to explore the relationship between residual inflammation in the middle ear cavity and development of mastoid pneumatization. Histopathological changes were studied in the middle ear cavity. Mastoid pneumatization was classified as good or poor based on the extent of mastoid tip development to the lateral semicircular canal. Specimens were 344 temporal bones with well-pneumatized mastoid and 51 with poorly-pneumatized mastoid. Otitis media was noted in 119 (34.6%) bones in the good group and 9 (17.6%) in the poor group. In well-pneumatized mastoid, chronic inflammatory changes were frequently observed at the lower portion of mastoid cells, the round window niche, and the tympanic sinus. In contrast, no such incidence of inflammatory change was noted in poorly-pneumatized mastoid. Our findings indicate that an intact tympanic membrane does not always mean freedom from mastoid inflammation, especially when the mastoid is well-pneumatized. This makes it important to check for possible remaining otitis media in patients with a well-pneumatized mastoid, even if the tympanic membrane appears normal.

Ear, Middle↗
PubMed2000

Preliminary results of a new delivery system for gentamicin to the inner ear in patients with Meniere's disease.

Intratympanic gentamicin therapy has gained some clinical popularity in the treatment of vertigo associated with Meniere's disease. This therapeutic modality offers some advantages over traditional surgical treatment. The vestibulotoxic effect of gentamicin is well documented, but there is no general agreement about the dose needed to control vertigo attacks without affecting hearing. In the current preliminary study 27 patients with Meniere's disease refractory to medical management were treated by small doses of gentamicin delivered via microcatheter in the round window niche and administered by an electronic micropump. The patients received a total dose of 0.24-90 mg. The effect on vestibular symptoms resulted in the cessation of vertigo in the 22 patients, control of drop attacks in 4 of 6, and release of aural pressure and fullness in 2 of 4. Significant hearing loss (anacusis) occurred in six patients, slightly related to the flow rate in the pump setting. Different explanations for the loss of hearing are presented. The new delivery system for gentamicin appears to be effective in controlling vertigo, but with an unacceptable negative effect on hearing. The effectiveness and the safety of this new delivery system must be investigated further in controlled studies. However, it opens up the possibility of future novel ways of treating inner ear diseases, such as sudden deafness and tinnitus, as well as for the protection, repair, and regeneration of inner ear sensory cell function in damage due to aging, noise, toxic substances, immune reactions, etc.

Adult↗
PubMed2001

Electrically evoked otoacoustic emissions from the chicken ear.

The outer hair cell electromotile response is believed to underlie the sharp tuning and exquisite sensitivity of the mammalian inner ear, and contribute to the production of electrically evoked otoacoustic emissions (EEOAEs) and sound-evoked otoacoustic emissions (OAEs). Avian ears are also sharply tuned, extremely sensitive and generate spontaneous and sound-evoked OAEs, but avian hair cells do not exhibit somatic electromotility. However, stereocilia bundle movements have been observed in avian and amphibian hair cells suggesting that EEOAEs might arise from electrically evoked bundle movements. Here, we demonstrate for the first time that AC current applied to the round window of the chicken evokes EEOAE of up to 18 dB SPL. The EEOAE produces a bandpass response with maximum amplitude in the 1000-3000 Hz range; the response drops off rapidly above 4000 Hz and below 500 Hz. The impulse response to current pulses is characterized by a large peak sometimes followed by a damped oscillation with a frequency around 2000 Hz. EEOAEs decreased significantly after anoxia and paraformaldehyde damage of the cochlea. Kanamycin-induced hair cell loss also caused a significant reduction in EEOAE and distortion product OAE; these emissions showed only a small recovery at long recovery times, when most hair cells should have regenerated. These results suggest that the EEOAE has a biological origin in the cochlea, which could presumably involve electrically evoked stereocilia bundle movements.

Animals↗
PubMed1985

[Implantation technics for long-term recording of the compound action potentials in the guinea pig, Cavia porcellus. A comparison of methods].

Long-term recordings of the compound action potential of the acoustic nerve of young, pigmented guinea pigs were carried out by two different techniques of implantation. The electrodes were inserted either by way of the mastoid process into the bony recess above the round window or they were introduced into the facial canal via the stylomastoid foramen. Before and after each implantation, special tests (Preyer-reflex, otoscopy, impedance audiometry) were performed for preliminary selection of the animals and to discover postoperative induced disturbances of sound conduction in the middle ear. These tests showed that the proportion of operatively induced middle ear inflammations was reduced from 24 to 10%, if electrodes were implanted into the facial canal.

Acoustic Impedance Tests↗
PubMed1989

[Idiopathic perilymph fistula].

This article presents 6 cases with idiopathic perilymph fistulae. The etiology of idiopathic perilymph fistula may be congenital malformation of the otic capule. Diagnosis of idiopathic perilymph fistula primarily depends on history and exploratory tympanotomy, but ENG-fistula test and positional audiometry are worth of diagnosing. During microsurgical procedure, attention must be paid to the presence of membrane of the round window niche. If a good repair of fistula is not followed by a good result, other lesions such as double labyrinth membrane rupture should be considered.

Adult↗
PubMed1988

[Assessment of the effect of piracetam (Nootrop) on hydrogen clearance in the inner ear].

The animal experiment described in this report was conducted to study the effect of piracetam on the blood flow of the inner ear. Blood flow was measured indirectly by means of hydrogen clearance using the polarographic microanalysis technique. A group of twelve crossbred male and female guinea pigs were given 400 mg/kg body weight piracetam (2 ml/kg body weight of commercial solution for injection) by intravenous injection, and hydrogen clearance was measured before and after administering the study drug at the round window in the scala media at the base of the cochlea. Twelve animals in an control group were given an equal volume of physiological saline instead of the study drug. The H2 clearance measurements were taken before and after intravenous injection of saline. The operation and clearance measurements were performed under injection anaesthesia with 2.5 mg. diazepam and 25 mg. pentobarbital sodium, each per kg body weight. The guinea pigs were premedicated with atropine (0.5 mg./kg. body weight i.p.) and, after tracheotomy, were relaxed with pancuronium bromide (1 mg./kg. body weight i.v.) and respirated with a pneumatic respiration pump and the parameters blood pressure, pH and blood gases (pO2, pCO2) were continuously recorded. The results show that intravenous injection of piracetam in the above mentioned dose accelerates hydrogen clearance processes at the base of the cochlea from 8.68 +/- 3.48 to 5.37 +/- 2.05 minutes half-life. This effect is statistically significant (p less than 0.005).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗