Core cutter for harvesting cortical bone grafts for reconstructions of the ossicular chain.
(1/66)
Cortical bone autografts have been used to reconstruct the ossicular chain for more than 30 years. We describe a core cutter burr which facilitates the rapid harvesting of grafts which are suitable for a number of different types of reconstruction. The use of these grafts to reconstruct different defects of the ossicular chain is also presented. (+info)
A new mammaliaform from the early Jurassic and evolution of mammalian characteristics.
(2/66)
A fossil from the Early Jurassic (Sinemurian, approximately 195 million years ago) represents a new lineage of mammaliaforms, the extinct groups more closely related to the living mammals than to nonmammaliaform cynodonts. It has an enlarged cranial cavity, but no postdentary trough on the mandible, indicating separation of the middle ear bones from the mandible. This extends the earliest record of these crucial mammalian features by some 45 million years and suggests that separation of the middle ear bones from the mandible and the expanded brain vault could be correlated. It shows that several key mammalian evolutionary innovations in the ear region, the temporomandibular joint, and the brain vault evolved incrementally through mammaliaform evolution and long before the differentiation of the living mammal groups. With an estimated body weight of only 2 grams, its coexistence with other larger mammaliaforms with similar "triconodont-like" teeth for insectivory within the same fauna suggests a great trophic diversity within the mammaliaform insectivore feeding guild, as inferred from the range of body sizes. (+info)
Nievergelt-Pearlman syndrome with impairment of hearing. Report of three cases in a family.
(3/66)
Three cases of the Nievergelt-Pearlman syndrome occurring in a family are presented. In addition to the major features of the syndrome (symphalangism, carpal fusion, atypical club foot with massive tarsal fusion, and congenital dislocation of the head of the radius), all three patients exhibited conductive deafness, which had not been recorded in previous reports. The clinical findings strongly suggested that the loss of hearing was due to fusion of the ossicles of the middle ear. (+info)
Peripheral specialization for fine analysis of doppler-shifted echoes in the auditory system of the "CF-FM" bat Pteronotus parnellii.
(4/66)
Pteronotus parnellii uses the second harmonic (61-62 kHz) of the CF component in its orientation sounds for Doppler-shift compensation. The bat's inner ear is mechanically specialized for fine analysis of sounds at about 61-62 kHz. Because of this specialization, cochlear microphonics (CM) evoked by 61-62 kHz tone bursts exhibit prominent transients, slow increase and decrease in amplitude at the onset and cessation of these stimuli. CM-responses to 60-61 kHz tone bursts show a prominent input-output non-linearity and transients. Accordingly, a summated response of primary auditory neurones (N1) appears not only at the onset of the stimuli, but also at the cessation. N1-off is sharply tuned at 60-61 kHz, while N1-on is tuned at 63-64 kHz, which is 2 kHz higher than the best frequency of the auditory system because of the envelope-distortion originating from sharp mechanical tuning. Single peripheral neurones sensitive to 61-62 kHz sounds have an unusually sharp tuning curve and show phase-locked responses to beats of up to 3 kHz. Information about the frequencies of Doppler-shifted echoes is thus coded by a set of sharply tuned neurones and also discharges phase-locked to beats. Neurones with a best frequency between 55 and 64 kHz show not only tonic on-responses but also off-responses which are apparently related to the mechanical off-transient occuring in the inner ear and not to a rebound from neural inhibition. (+info)
CT virtual endoscopy of the auditory ossicular chain: clinical applications.
(5/66)
OBJECTIVE: To evaluate the clinical applications and limitations of CT virtual endoscopy (CTVE) in the auditory ossicular chain. METHODS: CTVE of the auditory ossicular chain was performed with 1.0 mm collimation at pitch 1.0, bone algorithm, 9.6 cm field of view, and 0.1-0.2 mm reconstruction interval in 40 patients with middle ear diseases. 30 cases were confirmed by surgery. Results were compared with the findings of axial high resolution CT (HRCT) and multiplanar reformation (MPR) images and surgery. RESULTS: The accuracy of CTVE images in detecting ossicular destruction was 92.6%, significantly higher than that of axial HRCT (83.9%) and multiplanar reformation (76.5%) images. CTVE could also clearly reveal the postoperative condition and congenital dysplasia of the auditory ossicular chain. CONCLUSIONS: CTVE can clearly demonstrate a three-dimensional image of the auditory ossicular chain and is useful in evaluating diseases of the ear, especially the auditory ossicles. CTVE could not clearly demonstrate abnormal soft tissue within the tympanic cavity, abnormal changes of the tympanic membrane and tympanic walls, and could be easily influenced by artificial factors. (+info)
Specification of jaw subdivisions by Dlx genes.
(6/66)
The success of vertebrates was due in part to the acquisition and modification of jaws. Jaws are principally derived from the branchial arches, embryonic structures that exhibit proximodistal polarity. To investigate the mechanisms that specify the identity of skeletal elements within the arches, we examined mice lacking expression of Dlx5 and Dlx6, linked homeobox genes expressed distally but not proximally within the arches. Dlx5/6-/- mutants exhibit a homeotic transformation of lower jaws to upper jaws. We suggest that nested Dlx expression in the arches patterns their proximodistal axes. Evolutionary acquisition and subsequent refinement of jaws may have been dependent on modification of Dlx expression. (+info)
Vibrometric studies of the middle ear of the bullfrog Rana catesbeiana II. The operculum.
(7/66)
The operculum and stapes footplate, the two moveable elements within the oval window of the frog, have been thought to function independently. In this study, laser interferometry was used to record the vibrations of both structures in response to free-field airborne sound. Contrary to expectation, the operculum appears to be coupled to the footplate. Coupling is achieved both by means of ligaments and by a cartilaginous flange of the footplate that underlies the operculum. The stapes footplate rotates about an axis located ventrolaterally, but the axis for the operculum is dorsomedial. As a result of this unusual morphology, the opercularis muscle, which connects the operculum and shoulder girdle, can potentially affect the movements of both the operculum and footplate. The proposed roles of the opercularis system in seismic signal detection and extratympanic sound transmission are critically reviewed in the light of this new evidence. An alternative or additional role for the opercularis system is proposed, involving the protection of the inner ear from high-amplitude displacements of the stapes footplate during breathing and vocalisation. (+info)
Diagnostic utility of laser-Doppler vibrometry in conductive hearing loss with normal tympanic membrane.
(8/66)
HYPOTHESIS: It was hypothesized that laser-Doppler vibrometry measurements of umbo velocity in aerated middle ears with conductive loss can differentiate ossicular interruptions, stapes fixations, and mallear fixations. More generally, we hypothesize that laser-Doppler vibrometry measurements of umbo velocity can give information about how differences in the impedance that the ossicles work against affect middle-ear function. BACKGROUND: Laser-Doppler vibrometry is a well-established research tool for exploring middle-ear function. The authors wished to investigate its potential as a clinical tool for differential diagnosis of the cause of conductive hearing loss. METHODS: Laser-Doppler vibrometry was used to investigate the relationship between the sound-induced velocity of the tympanic membrane at the umbo and the cause of conductive hearing loss when the tympanic membrane was normal and the middle ear was aerated. The results of measurements in 17 adult ears before exploratory tympanotomy were compared with the surgically determined cause of the hearing loss. The authors also measured the motion of the umbo in 10 patients who had undergone successful small-fenestra stapedectomy procedures. In all the studied ears, pure-tone audiograms were measured at the time of laser-Doppler vibrometry testing. RESULTS: There were clear statistical differences between the umbo velocity in normal ears and in ears with different ossicular pathologic conditions. There was also a clear separation of the results between ears with ossicular interruptions and ossicular fixation. The pattern of laser-Doppler vibrometry measurements in poststapedectomy ears approximated the pattern in ears with ossicular interruptions. CONCLUSION: Comparison of laser-Doppler vibrometry results and audiometry may be a sensitive and selective indicator of ossicular pathologic conditions as well as a useful tool for investigating middle ear function. (+info)