Postmortem changes in ear canal resonance and tympanic membrane impedance in the human ear

BACKGROUND: The human temporal bone preparation is a common model for research of physical processes of the ear canal and middle ear. In the past decade only a few reports were published discussing changes of the vibration behaviour of the tympanic membrane, as well as the ear canal resonance, during the time between death and preparation of the temporal bone. The aim of our study is to verify whether measurements at the temporal bone of dead humans can be really applied to the in vivo situation. METHODS: We investigated whether changes of the ear canal resonance and the vibration of the tympanic membrane depend on temperature and time after death. In a female human body we defined the resonance of the outer ear and the impedance of the tympanic membrane using a tympanometer and a real ear measurement system during nine hours post mortem. RESULTS: We were able to prove that before the preparation of the temporal bone none of the parameters changed significantly. CONCLUSIONS: In conclusion, the method of preserving the bone after its preparation is decisive for the validity of measurements at the isolated (post mortem) human temporal bone.     

Histopathological studies of temporal bones of patients with malignant melanoma

Although malignant melanoma is known to metastasize to various sites including the temporal bones, there have been few studies on temporal bone histopathology in malignant melanoma. Here we describe the temporal bone histopathology of 5 patients (10 temporal bones) who died of malignant melanoma with multiple metastasis to many internal organs and bones. We investigated the temporal bone based on the following three points: 1) the presence of metastatic lesions in the temporal bone, 2) inner ear pathology, and 3) the distribution of melanin in the inner ear. Normal melanin distribution was also studied in 35 temporal bones of patients without malignant melanoma. Metastatic malignant melanoma was observed in 5 temporal bones from 3 patients, in two of whom the internal auditory canal was involved bilaterally by melanoma cell infiltration. In the remaining patient (one ear), metastatic melanoma was found along the dura mater of the posterior cranial fossa to the mastoid air cells. In the former two patients, the inner and outer hair cells as well as the stria vascularis showed degenerative changes to various extents. In particular, the inner ear changes were severe in the ear with the decongestion of the inner ear vessels. Melanin was found in the modiolus, stria vascularis, osseous spiral lamina, membranous labyrinth, and endolymphatic sac, as previously reported. The amount of melanin in the inner ear increased with age in the control patients, but was greater than in the controls, in all of the cases of malignant melanoma except one, in which metastatic lesions were present in the internal auditory canal with marked congestion of the inner ear vessels.     

Temporal bone imaging

Ameliorated computed tomography techniques and new magnetic resonance sequences have led to an important improvement in temporal bone imaging. Computed tomography is still the method of choice for imaging of temporal bone fractures, middle ear disease, and conductive hearing loss, although magnetic imaging can add important information. Patients with lesions of the cerebellopontine angle; internal auditory canal; inner ear; and, in general, all patients with sensorineural hearing loss, vertigo, and tinnitus are best examined with magnetic resonance imaging. In some cases, however, such as congenital malformations and petrous apex lesions, magnetic resonance imaging and computed tomography are complementary. The value of both modalities is discussed.     

Head-related transfer functions of the barn owl: measurement and neural responses

Sounds arriving at the eardrum are filtered by the external ear and associated structures in a frequency and direction specific manner. When convolved with the appropriate filters and presented to human listeners through headphones, broadband noises can be precisely localized to the corresponding position outside of the head (reviewed in Blauert, 1997). Such a 'virtual auditory space' can be a potentially powerful tool for neurophysiological and behavioral work in other species as well. We are developing a virtual auditory space for the barn owl, Tyto alba, a highly successful auditory predator that has become a well-established model for hearing research. We recorded catalogues of head-related transfer functions (HRTFs) from the frontal hemisphere of 12 barn owls and compared virtual and free sound fields acoustically and by their evoked neuronal responses. The inner ca. 1 cm of the ear canal was found to contribute little to the directionality of the HRTFs. HRTFs were recorded by inserting probetube microphones to within about 1 or 2 mm of the eardrum. We recorded HRTFs at frequencies between 2 and 11 kHz, which includes the frequencies most useful to the owl for sound localization (3-9 kHz; Konishi, 1973). Spectra of virtual sounds were within +/- 1 dB of amplitude and +/- 10 degrees of phase of the spectra of free field sounds measured near to the eardrum. The spatial pattern of responses obtained from neurons in the inferior colliculus were almost indistinguishable in response to virtual and to free field stimulation.     

Total facial nerve decompression: technique to avoid complications

Exposure of the facial nerve from the brainstem to the parotid can be accomplished without injury to the nerve, tympanic membrane, external auditory canal, ossicular chain, inner ear or structures within the cerebello-pontine angle. The procedure has reliably provided good results for patients who have had the proper indications with facial paralysis from Bell's palsy, herpes zoster oticus, infection, hemi-facial spasm, temporal bone fracture and tumors. The current technique for exposure through the mastoid, middle cranial fossa and retrolabyrinthine combined approaches are described. This technique, properly performed, is a valuable treatment for facial nerve lesions.     

Temporal bone findings in Pierre Robin syndrome

This is the first complete report on the histopathologic study of the temporal bones from an infant with a well-documented Pierre Robin syndrome (micrognathia, glossoptosis and cleft palate), demonstrating multiple middle and inner ear anomalies. The anomalies are basically architectural malformations rather than neutral or end organ developmental anomalies. The anomalies in this case, except for a few points, are somewhat similar in both ears. Multiple anomalies include: abnormal narrowing of the crus commune-utricle junction, superiorly located crus commune and posterior semicircular canal, underdeveloped modiolus, absence of the bony septum between the middle and apical coil (existence of scala communis in left ear), abnormally small internal auditory meatus, and abnormal direction of internal auditory canal, large cartilaginous mass around the superior semicircular canal and in the tympanic end of the fissula ante fenestram, small facial nerve, large facial bony canal dehiscence, anomalic stapes, etc.     

Echocardiographic spectrum of supracardiac total anomalous pulmonary venous connection

We report an unusual case of a 13-year-old girl with a benign osteoma associated with a cholesteatoma in the external auditory canal and serous otitis media. The osteoma was located in the antero-inferior wall of the right external auditory canal. A cholesteatoma was present between the osteoma and the tympanic membrane. Computed tomography revealed a soft tissue density within the external auditory canal and in the middle ear cleft. The shadow in the middle ear cleft was considered to represent the serous otitis media. Surgical removal of the osteoma and cholesteatoma proved successful, and no recurrences or complications have occurred in the first year postoperatively.     

Infrared temperature measurement in the ear canal with the DIATEK 9000 Instatemp and the DIATEK 9000 Thermoguide. Comparison with methods of temperature measurement in other body parts

Temperature of the tympanic membrane is recommended as a "gold standard" of core-temperature recording. However, use of temperature probes in the auditory canal may lead to damage of tympanic membrane. Temperature measurement in the auditory canal with infrared thermometry does not pose this risk. Furthermore it is easy to perform and not very time-consuming. For this reason infrared thermometry of the auditory canal is becoming increasingly popular in clinical practice. We evaluated two infrared thermometers-the Diatek 9000 Thermoguide and the Diatek 9000 Instatemp-regarding factors influencing agreement with conventional tympanic temperature measurement and other core-temperature recording sites. In addition, we systematically evaluated user dependent factors that influence the agreement with the tympanic temperature. MATERIALS AND METHODS: In 20 volunteers we evaluated the influence of three factors: duration of the devices in the auditory canal before taking temperature (0 or 5 s), interval between two following recordings (30, 60, 90, 120, 180 s) and positioning of the grip relative to the auditory-canal axis (0, 60, 180 and 270 degrees). Agreement with tympanic contact probes (Mon-a-therm tympanic) in the contralateral ear was investigated in 100 postoperative patients. Comparative readings with rectal (YSI series 400) and esophageal (Mon-a-therm esophageal stethoscope with temperature sensor) probes were done in 100 patients in the ICU. The method of Bland and Altman was taken for comparison. RESULTS: Shortening of the interval between two consecutive readings led to increasing differences between the two measurements with the second reading decreasing. A similar effect was seen when positioning the infrared thermometers in the auditory canal before taking temperatures: after 5 s the recorded temperatures were significantly lower than temperature recordings taken immediately. Rotation of the devices out of the telephone handle position led to increasing lack of agreement between infrared thermometry and contact probes. Mean differences between infrared thermometry (Instatemp and Thermoguide, CAL-Mode) and tympanic probes were -0.41 +/- 0.67 degree C (2 SD) and -0.43 +/- 0.70 degree C, respectively. Mean differences between the Thermoquide (Rectal-Mode) and rectal probe were -0.19 +/- 0.72 degree C, and between the Thermoguide (Core Mode) and esophageal probe -0.13 +/- 0.74 degree C. DISCUSSION: Although easy to use, infrared thermometry requires careful handling. To obtain optimal recordings, the time between two consecutive readings should not be less than two min. Recordings should be taken immediately after positioning the devices in the auditory canal. Best results are obtained in the 60 degrees position with the grip of the devices following the ramus mandibulae (telephone handle position). The lower readings of infrared thermometry compared with tympanic contact probes indicate that the readings obtained represent the temperature of the auditory canal rather than of the tympanic membrane itself. To compensate for underestimation of core temperature by infrared thermometry, the results obtained are corrected and transferred into core-equivalent temperatures. This data correction reduces mean differences between infrared recordings and traditional core-temperature monitoring, but leaves limits of agreement between the two methods uninfluenced.     

Acoustic mechanisms: canal wall-up versus canal wall-down mastoidectomy

The contribution of the middle ear air spaces to sound transmission through the middle ear in canal wall-up and canal wall-down mastoidectomy was studied in human temporal bones by measurements of middle ear input impedance and sound pressure difference across the tympanic membrane for the frequency range 50 Hz to 5 kHz. These measurements indicate that, relative to canal wall-up procedures, canal wall-down mastoidectomy results in a 1 to 5 dB decrease in middle ear sound transmission below 1 kHz, a 0 to 10 dB increase between 1 and 3 kHz, and no change above 3 kHz. These results are consistent with those reported by Gyo et al. (Arch Otolaryngol Head Neck Surg 1986;112:1262-8), in which umbo displacement was used as a measure of sound transmission. A model analysis suggests that the reduction in sound transmission below 1 kHz can be explained by the smaller middle ear air space volume associated with the canal wall-down procedure. We conclude that as long as the middle ear air space is aerated and has a volume greater than 0.7 ml, canal wall-down mastoidectomy should generally cause less than 10 dB changes in middle ear sound transmission relative to the canal wall-up procedure.     

Petrous bone tumors: primary non-Hodgkin lymphoma of the inner ear canal and cerebellopontile angle

BACKGROUND: We report about a primary Non-Hodgkin Lymphoma (NHL) of the internal auditory canal. The only previously known manifestations of a NHL in the temporal bone have been infiltrations or hemorrhagic complications due to a late manifestation or advanced systemic disease. Involvement of both temporal bones is typical. CLINICAL CASE: The 60-year-old female patient complained of an acute one-sided deafness, accompanied by a high-pitched tinnitus, rotating vertigo, and paralysis of the left half of the face. RESULTS: We found a deafness in the left ear, spontaneous nystaxis, which was interpreted as a deficiency in excitement of the vestibular organ, and a complete peripheral facial paralysis. Diagnostic imaging studies revealed a large, intrameatal solid mass in the temporal bone, measuring 1.2 x 0.8 cm. Histologic examination after translabyrinthine tumor removal demonstrated a centroblastic Non-Hodgkin Lymphoma. The following extensive interdisciplinary staging examination showed no other tumor manifestations; the CSF analysis was negative. CONCLUSIONS: The uniqueness of this case lies in the detection of a primary nongeneralized centroblastic lymphoma of the internal auditory canal. In contrast to infiltrations of systemic NHL in the same location, in which the advanced disease is responsible for the bad prognosis, this isolated lymphoma of the internal auditory canal seems analogous to extranodal MALT Lymphomas with a better prognosis. The primary extranodal NHL of the temporal bone, not reported in previous studies, is discussed with regard to clinical symptoms, differential diagnoses, and therapeutic strategies.     

Relationship between evoked otoacoustic emissions and middle-ear dynamic characteristics

Evoked otoacoustic emissions (EOAEs) are considered to originate from outer hair cell movement and to be transmitted to the external auditory meatus through the ossicular chain and eardrum in a retrograde fashion. Therefore, the effect of the middle ear on EOAEs seems to be large. A sweep frequency middle-ear analyzer (MEA) has been developed that gives much more information on middle-ear dynamic characteristics than a conventional impedance meter. In this paper, applying our own EOAE measuring system and the MEA, EOAEs and middle-ear dynamic characteristics of normal subjects were measured, and an attempt was made to clarify the relationship between EOAEs and middle-ear dynamic characteristics. It is concluded that EOAEs are detected most distinctly at the middle-ear resonance frequency and that EOAEs are most detectable in normal subjects whose middle-ear mobility is moderate.     

Effects of WR-2721 (amifostine) and its metabolite WR-1065 on the antiproliferative activity of chemotherapeutic agents on neuroblastoma cells in vitro

Approaches through the middle cranial fossa directed at reaching the internal auditory canal (IAC) invariably employ exposure of the geniculate ganglion, the superior semicircular canal (SSC) or the epitympanum. This involves risk to the facial nerve and hearing apparatus. To minimize this risk, we conducted a laboratory study on 9 cadaver temporal bones by using an image-interactive guidance system (StealthStation) to provide topographic orientation in the middle fossa approach. Surface anatomic fiducials such as the umbo of the tympanic membrane, Henle's spine, the root of the zygoma and various sutures were used as fiducials for registration of CT-images of the temporal bone. Accurate localization of the IAC was achieved in every specimen. Mean target localization error varied from 1.20 to 1.38 mm for critical structures in the temporal bone such as the apex of the cochlea, crus commune, ampula of the SSC and facial hiatus. Our results suggest that frameless stereotaxy may be used as an alternative to current methods in localizing the IAC in patients with small vestibular schwannomas or intractable vertigo undergoing middle fossa surgery.     

Radiation therapy in the management of carcinoma of the external auditory canal, middle ear, or mastoid

Twenty-three patients with squamous-cell carcinoma of the external auditory canal, middle ear, or mastoid were treated with combined surgery and irradiation, giving a 5-year NED rate of 48% (11/23). Except in extremely early lesions without bone involvement, treatment by radiation therapy alone was rarely successful and is not recommended. The most serious complication was osteoradionecrosis of the temporal bone; this occurred in 5 patients, all of whom received more than 2,100 rets due to faulty radiotherapeutic technique.     

Herniation of the singular nerve into the round window niche

We report two cases of herniation of the singular nerve into the round window niche and one case of bony dehiscence without herniation between the round window niche and the posterior canal ampulla. It is believed that the middle ear and the inner ear are completely separate. However, in the temporal bone of a 10- to 15-week-old human fetus, a communication between the round window niche and the posterior canal ampulla is observed. Later, the mesenchymal tissue in the communication is replaced by cartilage from near the posterior canal ampulla. If the communication does not fill with cartilage, ossification is not able to begin behind the posterior canal crista. When there is bony dehiscence behind the crista, the singular nerve fibers are easily pressed out by ossified endosteal bone and herniated into the round window niche.     

An evaluation of tympanometric estimates of ear canal volume

The accuracy of tympanometric estimates of ear canal volume was evaluated by testing the following two assumptions on which the procedure is based: (a) ear canal volume does not change when ear canal pressure is varied, and (b) an ear canal pressure of 200 daPa drives the impedance of the middle ear transmission system to infinity so the immittance measured at 200 daPa can be attributed to the ear canal volume alone. The first assumption was tested by measuring the changes in ear canal volume in eight normal subjects for ear canal pressures between +/- 400 daPa using a manometric procedure based on Boyle's gas law. The data did not support the first assumption. Ear canal volume changed by a mean of .113 ml over the +/- 400 daPa pressure range with slightly larger volume changes occurring for negative ear canal pressures than for positive ear canal pressures. Most of the volume change was attributed to movement of the probe and to movement of the cartilaginous walls of the ear canal. The second assumption was tested by comparing estimates of ear canal volume from susceptance tympanograms with a direct measurement of ear canal volume adjusted for changes in volume due to changes in ear canal pressure between +/- 400 daPa. These data failed to support the second assumption. All tympanometric estimates of ear canal volume were larger than the measured volumes. The largest error (39%) occurred for an ear canal pressure of 200 daPa at 220 Hz, whereas the smallest error (10%) occurred for an ear canal pressure of -400 daPa at 660 Hz. This latter susceptance value (-400 daPa at 660 Hz) divided by three is suggested to correct the 220-Hz tympanogram to the plane of the tympanic membrane. Finally, the effects of errors in estimating ear canal volume on static immittance and on tympanometry are discussed.     

Induction of pulmonary tissue maturation in premature infants

Bleeding from the external auditory canal following head trauma is not unusual. It can be caused by a posterior dislocation of the mandibular condyle associated with a fracture of the tympanic bone. Although posterior dislocation is uncommon, it is the second most frequent complication after antero-medial displacement of the condyle. We report four cases of tympanic plate fracture and present CT images demonstrating the range of injuries seen.     

Distortion product otoacoustic emissions in human newborns and adults. I. Frequency effects

This study varied stimulus frequency and recorded distortion product otoacoustic emissions (DPOAEs) in human newborns and adults. Because of outer and middle ear acoustics, the same auditory input resulted in higher newborn stimulus sound pressure levels across a broad frequency range in the occluded outer ear canal. Noise levels in the canal were 5-15 dB lower for adults at frequencies less than about 3 kHz. The 2 f1-f2 DPOAE was the most reliably recorded DPOAE except at the lowest frequencies assessed. At the lowest frequencies the 2 f2-f1 DPOAE was more frequently recorded than any other DPOAE. There were no striking developmental differences in the kinds of DPOAEs that were recorded. The amplitudes of consecutively recorded 2 f1-f2 DPOAEs were generally within 1.5 dB of each other for all age groups (slightly better reproducibility for adults than newborns). The phases of consecutively recorded 2 f1-f2 DPOAEs were generally within 15 degrees of each other (often less than 10 and 5 degrees for newborns and adults respectively). At the highest frequencies assessed (f2 = 4.2-9.9 kHz) all subjects had similar amplitude 2 f1-f2 DPOAEs. At lower frequencies adult 2 f1-f2 amplitudes were significantly less than those of newborns. At the lowest frequencies reliably assessed (f2 = 1.5-2.1 kHz) term newborns had significantly larger 2 f1-f2 DPOAEs than preterm newborns. Newborn and adult 2 f1-f2 DPOAE amplitude X f2/f1, functions were quite similar although there were reliable differences. Age related differences in the outer and middle ears may explain some of the differences in DPOAEs that were observed.     

Tympanometric detection of middle ear effusion in infants and young children

Tympanometry, a test of middle ear status new to clinical pediatrics, was carried out on 280 subjects, 10 days through 5 years of age. The tympanograms obtained were compared with otoscopic findings and, in 107 of the subjects, with findings at myringotomy. Seven distinct tympanometric curve types were identified and defined, based on their degree of correlation with the presence or absence of middle ear effusion. In subjects 7 months of age and older, curves suggesting normal (high) tympanic membrane compliance in combination with atmospheric or near-atmospheric middle ear air pressure were rarely associated with effusion. Conversely, curves suggesting low tympanic membrane compliance were highly correlated with the presence of effusion. Curves suggesting intermediate compliance or reduced middle ear air pressure were also correlated with effusion, but the degree of correlation was dependent on the shape of the curve. In infants less than 7 months of age, many of the ears with effusion had "normal" tympanograms, presumably because external auditory canal walls in such infants tend to be highly distensible. Tympanometry is a simple, rapid, atraumatic, valid, and objective test, easily administered by paraprofessional personnel. Its use can result in improved detection of middle ear effusion and other middle ear abnormalities, and also appears to promote improvement in diagnostic acumen.     

Computer-stimulated test fitting of an implantable hearing aid using implantable hearing aid using three-dimensional CT scans of the temporal bone: preliminary study

In preparation for future implantation of the implantable middle ear transducer in patients, a method was sought for preoperatively test fitting a model of the device, using computer generated three-dimensional (3-D) temporal bone images derived from spiral computed tomography (CT) data. A 3-D model of the implantable middle ear transducer was designed using NIH Image software on a Macintosh computer. High resolution human temporal bone CT scans were obtained using a spiral CT scanner (Siemens Somatom Plus S). The 3-D transducer model was superimposed onto 3-D reconstructions of the temporal bone using ANALYZE software on a computer graphics workstation (Sun SPARCstation 10), showing the transducer "implanted" in the temporal bone. Measurements were validated using a cadaver temporal bone. This process produced images demonstrating the "fit" of the current transducer design in the mastoid region of the adult temporal bone. It permitted assessment of the proximity of surrounding structures such as the external auditory meatus, dura, or sigmoid sinus. Preliminary cadaver validation measurements confirmed the accuracy of this method. Three-dimensional CT is a feasible method for preoperative planning of the surgical implantation of devices in the temporal bone. This method of 3-D test fitting will be used in the future to determine optimum orientation and size limitations for human implantable devices.