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PubMed1999

Endoscopy of the middle ear through the eustachian tube: anatomic possibilities and limitations.

HYPOTHESIS: This anatomic study was designed to provide otosurgeons with a detailed description of the technique of transtubal middle ear endoscopy and anatomic landmarks facilitating orientation. To establish the role of transtubal endoscopy, its anatomical potentials and limitations were studied. BACKGROUND: Transtubal endoscopy has recently been described as an atraumatic tool for exploring the tympanic cavity. From the nasopharynx, a thin, flexible endoscope is advanced into the middle ear through the Eustachian tube. After the endoscope has been placed, it offers an anteroposterior view of the tympanic structures. METHODS: Temporal bone blocks and whole skulls of recently deceased persons were examined to define the average range of view obtained by transtubal endoscopy. Key structures in each region of the tympanic cavity were chosen for inspection, and positive identifications were noted. RESULTS: With a 0.8-mm, flexible, steerable scope, most mesotympanic structures (stapes suprastructure, incudostapedial joint, tympanic chord, and inner surface of the eardrum) were clearly defined. Areas of the posterior wall that were not accessible with the otomicroscope (lateral tympanic sinus, tympanic sinus, and facial recess) were also seen. Unlike with transtympanic endoscopy, the epitympanum (incudomalleal joint and malleus neck) was also evaluable. The stapes footplate was not seen well and the round window niche was unable to be inspected in the anteroposterior view inherent in the technique. Technical factors (poor illumination and small image size) and the unfamiliar anteroposterior view made orientation in the middle ear difficult. CONCLUSION: Transtubal middle ear endoscopy is a suitable method for exploring the tympanic cavity without traumatizing the eardrum.

Ear, Middle↗
PubMed2006

Middle ear ossicles motion at hearing thresholds with air conduction and bone conduction stimulation.

Hearing threshold data with bone conduction and air conduction stimulation are combined with physiological and mechanical measurements of the middle ear ossicles vibration to compute the vibration level of the ossicles at threshold stimulation. By comparing the displacements of the stapes footplate with the two stimulation modalities and assuming the vibration of the stapes footplate to be the input to the cochlea when stimulation is by air conduction, the importance of middle ear ossicles inertia with bone conduction stimulation is evaluated. Given the limitations of the analysis, the results indicate that the inertia of the middle ear is not an important contribution to the perception of BC sound for frequencies below 1.5 kHz; it seems to contribute to perception of bone conducted sound between the frequencies 1.5 and 3.5 kHz. At frequencies above 4 kHz, the analysis failed since the input to the cochlea is probably not through the oval window with bone conduction stimulation. Comparison of basilar membrane vibration data verified the calculations for frequencies between 0.8 and 3.5 kHz. It was also found that the fluid flow at the round window, rather than at the oval window, reflects the stimulation of the basilar membrane with bone conduction stimulation.

Acoustic Stimulation↗
PubMed1977

[CSF-rhinorrhea due to removal of an acoustic neuroma (author's transl)].

After removal of an acoustic neuroma by the suboccipital route cerebrospinal fluid rhinorrhea was observed. This procedure was complicated by meningitis and pneumatocephalus. Finally, after one neurosurgical and four otosurgical interventions, the cerebrospinal fluid leak was identified in the membrane of the round window. It was plugged with a fascial graft.

Adult↗
PubMedDate not supplied

Hearing preservation after inner ear gene therapy: the effect of vector and surgical approach.

Over seventy studies have examined the potential of gene therapy in the inner ear. For the most part, they have focused on adenoviral vectors and delivery into the cochlea. Most studies have emphasized looking at the expression of marker genes driven by a CMV promoter and have used first-generation adenoviral constructs. E1/E3/E4 deleted adenoviral vectors carrying the green fluorescent protein (GFP) gene were injected into the round window, the basal turn of the cochlea (via a cochleostomy) or into the superior semicircular canal. Hearing was then tested 24 h after viral gene transfer. Large vector titers in small volumes of fluid were well tolerated with the round window approach resulting in complete hearing preservation with transfer of GFP to hair cells and spiral ganglion cells. Injection of comparable doses of vector into a basal turn cochleostomy resulted in high-frequency hearing loss. Addition of a pancaspase inhibitor protected hearing when larger volumes of fluid were administered to the inner ear.

Adenoviridae↗
PubMed2000

Fine structure and multicomponents of the electrically evoked otoacoustic emission in gerbil.

Like the acoustically evoked distortion product otoacoustic emissions (DPOAE), the amplitude spectrum of the extracochlear electrically evoked otoacoustic emission (EEOAE) also shows peaks and valleys, which are termed the fine structure (FS) of the EEOAE. The hypothesis that the FS of the EEOAE is generated by multiple wave interactions in the cochlea is investigated by examining the relationship between the FS and the multiple-delay components of the EEOAE. The bulla of the gerbil was exposed using a ventral surgical approach. One pole of a bipolar electrode was placed in the round window niche, and the other pole on the surface of the first cochlear turn. A microphone was used to measure electrically evoked sound pressure change in the ear canal. A recently developed multicomponent analysis method was used to detect the EEOAE multiple delays. It was found that the FS is the spectral representation of the multiple-delay components. The relative power of a prominent long delay component (LDC) shows a negative relationship to the electrical stimulus level. Both the FS and the LDC were abolished by intravenous furosemide. Reconstructed signals showed that mathematical removal of the EEOAE LDC also completely eliminated the FS. These data demonstrate that the FS and the EEOAE multicomponents are properties of normal cochlear mechanics in a healthy ear and that the FS is a manifestation of the multicomponents. The findings in this study strongly indicate that the FS of the EEOAE evoked by extracochlear electrical stimulation is generated by wave interaction in the cochlea. The similarity between the EEOAE FS and the DPOAE FS suggests that they may share the same mechanism.

Animals↗
PubMed1987

Ototoxicity of neomycin and polymyxin B following middle ear application in the chinchilla and baboon.

Previous experimental studies have demonstrated structural damage of the organ of Corti and stria vascularis following application of combination antibiotic otic drops to the middle ear. In this investigation the ototoxic effects of neomycin and polymyxin B (two antibiotics often used together in ototopical preparations) were separately evaluated after administration of each agent to the middle ear cavities of chinchillas and baboons. The antibiotics were administered in saline solution at the same concentrations used in Cortisporin Otic Suspension (3.5 mg/ml neomycin base, 10,000 units/ml polymyxin B). In both the rodent and primate, polymyxin B consistently produced greater cochlear damage than did neomycin. In fact, the extent of hair cell loss and strial injury produced by polymyxin B alone was, in many cases, comparable to that previously observed after application of Cortisporin Otic Suspension itself. Hair cell loss in the baboon was markedly less severe than in the chinchilla. It is believed that differences in position and structure of the round window membrane are important factors in the differing levels of ototoxicity observed in the rodent and primate.

Animals↗
PubMed2000

[Histopathological studies of intratemporal growth behavior of middle ear carcinoma].

BACKGROUND: Otological hemorrhage otorrhea, and pain are amongst the first clinical signs of the middle ear carcinoma, which is usually diagnosed in advanced stages. Sudden deafness, facial nerve paralysis, and other symptoms of inner ear damage may be observed in the final stage. However, middle ear carcinoma is diagnosed extremely seldom in its early stages. The clinical management of this pathology is based on the knowledge of the tumor's pathways and its anatomic behavior. METHODS: Our study investigated 20 cases of middle ear carcinomas from the Wittmaack temporal bone bank (14 squamous cell carcinomas, 5 adenocarcinomas, and 1 adenoidcystic carcinoma) to analyze the behavior of the tumor growth and its influence on clinical symptoms. The aim was to determine criteria for early clinical diagnosis. RESULTS: The tumor arises in different regions of the temporal bone, and varying symptoms will subsequently reflect its pathway. When the tumor is confined to the middle ear area, its main location is the hypotympanum from which tumor spreads into the eustachian tube and, via infiltration of the adjacent bone structures (anterior wall of the middle ear), into the tensor tympani muscle and the sympathetic plexus of the internal carotid artery. Destruction of the ossicles was observed in the mid-tympanic cavity, and often only a thin layer of fibrous tissue from the Fallopian canal separated the tumor from the facial nerve (this nerve was rarely affected directly). The medial wall (labyrinthine wall) of the tympanic cavity remained intact in the majority of examined cases. The tympanic sinus, the round window niche, and the oval window niche did not show tumor infiltration. In the epitympanum, the tumor grew and infiltrated the adjacent mastoid. Larger tumors affected the internal auditory canal and infiltrated the acoustic nerve and the labyrinth. CONCLUSION: Improving the poor prognosis of middle ear carcinoma requires early diagnosis based on axial computed tomography (CT). Important factors in patient selection include age (50-70 years), sex (mostly women), and especially clinical symptoms (otorrhea, pain, hearing loss).

Adenocarcinoma↗
PubMed2004

Effect of edaravone on streptomycin-induced vestibulotoxicity in the Guinea pig.

OBJECTIVES/HYPOTHESIS: The effect of topical administration of edaravone to the inner ear was investigated in guinea pigs with streptomycin-induced vestibulotoxicity. METHODS: Vestibulotoxicity was induced in 20 animals by delivery of streptomycin into the inner ear through osmotic pump for 24 hours. Edaravone (n = 8, systemic administration group) or saline (n = 6, control group) was injected intraperitoneally once a day for 7 days or edaravone-soaked Gelfoam was placed on the round window before wound closure (n = 6, topical administration group). RESULTS: Yaw head tilt and spontaneous nystagmus were observed in all animals after the operation. The number of spontaneous nystagmus beats in the topical administration group was statistically less than that in other two groups at 12, 18, and 24 hours after the operation. CONCLUSION: The study results suggest that topical administration of edaravone better suppresses streptomycin-induced vestibulotoxicity than systemic administration.

Administration, Topical↗
PubMed1999

Chronic electrical stimulation by a cochlear implant promotes survival of spiral ganglion neurons after neonatal deafness.

This investigation examined the consequences of neonatal deafness and chronic intracochlear electrical stimulation delivered by a cochlear implant during maturation. Kittens were bilaterally deafened by an ototoxic drug administered daily for 2 weeks immediately after birth. Unilateral electrical stimulation was initiated at 7-10 weeks of age and continued over periods of 22-47 weeks (4 hours/day; 5 days/week). Bipolar intracochlear electrodes delivered one of several different electrical signals designed to be temporally challenging to the central auditory system. Morphometric evaluation of spiral ganglion (SG) cell somata within Rosenthal's canal demonstrated a mean of approximately 50% of normal cell density maintained in the chronically stimulated ears, compared with approximately 30% on the control deafened side. This 20% difference in density was highly significant and was greater than differences reported in earlier studies using 30 pps stimulation delivered by either intracochlear bipolar or round window monopolar electrodes. However, the duration of stimulation was also longer in the present study, so it is unclear to what extent the nature of the temporally challenging stimulation vs. its duration contributed to the marked increase in survival. Measurements of the SG cell somata revealed a pronounced decrease in cell diameter in neonatally deafened cats studied about 1 year after deafening, and an additional decrease after long-term deafness (2.5-6.5 years). Furthermore, in the cochlear regions with the greatest stimulation-induced differences in SG cell density, direct measurements of cross-sectional soma area of the largest cells revealed that cells were significantly larger in the stimulated ears. Thus, in addition to the marked increase in the number of surviving SG cells, larger soma area contributed modestly to the pronounced increase in neural density following chronic electrical stimulation.

Animals↗
PubMed1999

Hair cell protection from aminoglycoside ototoxicity by adenovirus-mediated overexpression of glial cell line-derived neurotrophic factor.

Aminoglycosides are commonly used antimicrobial drugs that often have ototoxic side effects. The ototoxicity often involves permanent loss of cochlear hair cells (HCs). Neurotrophic factors have been shown to protect a variety of tissues, including HCs, from toxic trauma. To determine if glial cell line-derived neurotrophic factor (GDNF) can protect cochlear HCs from trauma, we inoculated an adenoviral vector encoding the human GDNF gene into guinea pig cochleae via the round window membrane 4 days prior to injection of aminoglycosides. Control groups showed little or no negative influence of the viral inoculation on cochlear structure and function. In contrast, ears that were inoculated with the GDNF vector had better hearing and fewer missing HCs after exposure to the ototoxins, as compared with controls. Our results demonstrate the feasibility of gene therapy for cochlear application and suggest that virus-mediated overexpression of GDNF may be developed as a valuable prevention against trauma-induced HC death.

Adenoviridae↗
PubMed1995

Effect of endolymphatic hydrops on capsaicin-evoked increase in cochlear blood flow.

Capsaicin, which causes release of neuropeptides including substance P, has been shown to cause dose-related increases in cochlear blood flow (CBF). Since CBF regulation is altered in animal models with endolymphatic hydrops, this study was designed to examine the effect of hydrops on capsaicin-induced CBF changes. CBF responses to 0.01 and 0.001% capsaicin applied to the round window membrane were measured in normal and 12-week hydropic guinea pigs using laser Doppler flowmetry. With 0.01% capsaicin, CBF increased by only 13 +/- 7.8% in the hydropic ear, compared with 34% +/- 13% in the normal animal (p = 0.027). With 0.001% capsaicin, CBF increased by only 7.5 +/- 4.2% in the hydropic ear, compared with 28 +/- 16% in the normal ear (p < 0.001). These findings demonstrate a reduced responsiveness to capsaicin with endolymphatic hydrops and suggest that hydrops causes an alteration in the peptidergic sensory fibers of the inner ear or in the vascular smooth muscle or both. The results are consistent with previous reports of reduced vascular responsiveness in hydropic guinea pigs and provide further evidence for abnormal CBF regulation in hydrops.

Alkaloids↗
PubMed1990

Computer-aided 3-D temporal bone anatomy for cochlear implant surgery.

To define anatomical relationships important in cochlear implantation, computer-aided three-dimensional reconstruction and measurement of middle and inner ear structures in six normal temporal bones were performed. Our findings were as follows: 1. When viewed from the posterior hypotympanotomy (facial recess) approach, the inferior 10% to 30% of the round window (RW) membrane was visible in only half the cases. 2. The most inferior portion of the basal turn of the scala tympani was not only inferior but also slightly anteriorly behind the RW membrane in more than half the cases. 3. The shortest distances from the aperture of the RW niche and from the margin of the RW to the stapes head were 2.38 +/- 0.33 and 2.15 +/- 0.22 mm, respectively. 4. The distance between the RW and the most inferior portion of the basal turn scala tympani was 5.15 +/- 0.34 mm. 5. The direction of the electrode advancement lay at a sharp angle to the inferior part of the RW (mean 31.9 +/- 3.6 degrees). 6. The direction from the RW to the most inferior portion of the basal turn scala tympani lay 16.0 +/- 5.3 degrees anteroinferior to the direction of the advancement of the electrode to the RW. 7. The distance between the margin of the RW and the basilar membrane of the cochlea was 0.58 +/- 0.10 mm at the superior aspect of the RW, and was 1.23 +/- 0.12 mm at the lateral aspect of the RW. 8. Dissecting away less than 1 mm (mean 0.7 +/- 0.27 mm) of the RW margin inferiorly or inferolaterally was enough to permit straight insertion of the electrode in most cases.

Adolescent↗
PubMed1997

[The errors of the operative technique as a cause of unsuccessful tympanoplasty. Part II].

This study is based on the author's personal experience in a middle ear reconstructions. Errors can occur at each surgical stage--tympanic membrane and chain reconstructions, mobilisation of the footplate. At any moment the surgeon can gain or loose the dB. The operating technique is the main factor. A proper operative technic includes a good operating approach and excellent hemostasis. The tympanic membrane, should be as thin as possible, exactly and carefully dissected. Care should be taken to avoid any damage to the fascia graft fibers. Bad or unsure material should be discarded. The graft should not be too large because if it overlaps the EAC wall, it narrows the canal. If the graft is too small, secondary edge performation can occur. The shallow placement of the graft risk a bad contact. Opposite--too deep--poor ventilation of the middle ear and may lead to adhesions. The annulus should be well prepared, free of epithelial remnants. If not cholesteatoma could develop and discontinuity between the neotympanium and the ossicular chain abolish the transmission effect. The mechanical and lever principles during reconstruction of the sound transmission should be kept in mind at all times. The reconstructed system must be delicate and light. The round window reflex is the most important indice of good performed reconstruction, and should be used similar to the modern monitoring system. Try to prevent the natural structures. They are the most valuable material for the future reconstruction.

Ear Ossicles↗
PubMed1996

Auditory nerve neurophonic produced by the frequency difference of two simultaneously presented tones.

When two phase-locked sinusoidal stimuli having frequencies of F1 and F2 are simultaneously introduced to the ear of the gerbil, a difference tone (DT) can be observed (DT = F2-F1, where F2 > F1) in the time-averaged electrical response recorded from the cochlear round window (RW). Tetrodotoxin (TTX), which blocks the axonal firing of the cochlear nerve fiber, greatly attenuates this DT response, suggesting it is primarily neural in origin. Alternating the polarity of a single phase-locked tone cancels out the RW cochlear microphonic (CM) from the time-averaged response, leaving a residual auditory nerve neurophonic (ANN) response if the stimulus frequency is low enough to result in phase-locked firing of cochlear nerve axons. Simultaneous presentation of 1 kHz (F1) and 2 kHz (F2) tones, each being phase-locked with alternating polarity, produces a small ANN in response to the original tones and a large time-averaged ANN in response to the DT. Even when the frequency of the individual tones is too high to support phase-locking, a large DT-ANN can also be measured in response to simultaneously presented tones. A robust time-averaged DT-ANN can be measured when the temporal and intensity relationships between F1 and F2 are varied widely, with the latency (but not amplitude) of the response following the stimulus envelope. The DT-ANN produced by pairs of tones having frequencies ranging from 500 Hz to 3.5 kHz is largest in response to a DT of approximately 700-1100 Hz. This is in contrast to the ANN generated in response to a single tone, which decreases in magnitude as the stimulus frequency increases from 500 to 1500 Hz. Robust DT-ANNs can be measured from the gerbil even when the F2 frequency is greater than 30 kHz.

Acoustic Stimulation↗
PubMed1999

Auditory rehabilitation in neurofibromatosis type 2: a case for cochlear implantation.

Cochlear implantation has a limited but definite role in the rehabilitation of certain neurofibromatosis type 2 (NF2) patients. The presence of a dead ear either before, or after, tumour removal does not necessarily imply loss of function in the eighth nerve; in some instances the hearing loss will be cochlear. Promontory or round window electrical stimulation may help to identify those individuals with surviving eighth nerve function. In such patients multichannel cochlear implantation promises a better level of audition than the auditory brain stem implant. This paper highlights such a case and the management problems are discussed.

Adolescent↗
PubMed1999

Spread of amniotic fluid cellular content within the neonate middle ear.

Six full-term neonatal temporal bones, with meconium contaminated amniotic fluid aspiration of varying degrees, were serially sectioned at 20 microm and every tenth section was stained by hematoxylin eosin and mounted on slides. All stained sections were studied, the data recorded and relevant details of all compartments photographed. In addition, four normal neonate temporal bones were studied, one by serial sectioning and three by microdissection. The lateral incudomalleal and tensor folds were present in all, membrane defects in the tensor fold were seen in two normal ears. Three ears in the aspiration group had much fetal tissue present rendering Prussak's space small. Four ears with aspiration had remnants of incus intercrural (medial) folds. The amniotic fluid cellular content (AFCC) was sparse or nonexistent in the supratubal recess, Prussak's space and hypotympanum. It concentrated to the areas around the stapes, to sinus tympani and round window niche, to lower lateral attic and posterior pouch, medial attic and in lesser amounts to superior attic, mastoid antrum and air cells. Massive amounts of AFCC in tympanic isthmus and posterior pouch may lead to formation of granulation tissue and blockage of the aeration pathways to attic proper and to Prussak's space. These changes may initiate the development of chronic secretory otitis media in infants.

Amniotic Fluid↗
PubMed1995

[Preoperative X-ray computed tomographic evaluation of major aplasia of the ear in children].

PURPOSE: To describe computed tomography (CT) findings in congenital aural atresia (CAA) and to illustrate the impact of these findings in the preoperative evaluation. MATERIALS AND METHODS: Sixty-seven congenital aural atresia (bilateral: 10) in 57 children were studied using high resolution CT. Sections 1.5 mm thick were removed from the coronal and the axial plans without sedation (mean age: 9, 6 years). RESULTS AND DISCUSSION: A narrow bony external auditory canal (EAC) was present in 24% of the cases. In one of these cases, the EAC contained a cholesteatoma and was consequently a clear indication of surgery. An hyperpneumatized mastoïd (22%), a posterior position of the temporo mandibular joint (16%), and a bulging medial temporal fossa (12%) made the operation much more difficult. The tympanic cavity was small in 68% of the cases, normal in 28% and absent in 4% of the cases without any detectable ossicular chain. Ossicular chain anomalies were present in 91% of the cases. This consisted most frequently of a fusion of the malleus and the incus (76%) with or without fusion to the tympanic wall (33%). Lateral and anterior displacement of the descending portion of the facial nerve was present in 62%. Oval and round windows were normal in 86% of the cases. A soft tissue opacity (33%) in the tympanic cavity made it difficult to evaluate the stapes, the incudo stapedial articulation, and the facial nerve. Simultaneous abnormalities of inner ear were exceptional (1 case). CONCLUSION: High resolution CT is the best method in CAA evaluation and for guiding the planning of the surgical correction.

Child↗
PubMed1998

Differentiation of cochlear pathophysiology in ears damaged by salicylate or a pure tone using a nonlinear systems identification technique.

Mongolian gerbils were exposed to either alpha-ketoglutarate, salicylate, or an 8-kHz pure tone. Cochlear microphonic (CM) was recorded from the round window in response to 68 and 88 dB SPL Gaussian noise. A nonlinear systems identification technique provided the frequency-domain parameters of a third-order polynomial model characterizing cochlear mechano-electric transduction (MET). A series of physiologic indices were derived from further exploration of the model. Exposure to the 8-kHz pure tone and round window application of salicylate resulted in different changes in the polynomial parameters and physiologic indices even though the threshold shifts were similar. A general reduction of CM magnitude was found after the tone exposure, and an increase at low-mid frequencies was demonstrated in the salicylate group especially at the lower signal level. The slope of the MET curve was reduced by the acoustic overstimulation. The root or the operating point of the MET was shifted in opposite directions after the two treatments. Sound-pressure levels that saturate MET expanded in the tone exposure group and narrowed in the salicylate group. The signal level also had effects on these indices.

Animals↗