Biomedical subjects
Publications and source records attributed to A Uziel.
Recent experiments have shown the healing potential of growth factors in tissue repair. Epidermal interference and fibroblast growth factors in the healing of acute and chronic tympanic membrane perforations are reviewed and discussed.
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Choice of the side for cochlear implantation should take into account peripheral (extracortical) factors and central (cerebral dominance) factors. From 111 patients implanted with a Nucleus device, the authors found that significant peripheral factors were the degree of cochlear ossification, the duration of deafness before cochlear implantation, and the preoperative promontory test dynamic range (degree of response on the promontory test in decibels); cause of deafness and residual hearing were not correlated with speech discrimination. Cerebral dominance was indirectly determined by handedness. Handedness laterality was determined by a questionnaire. There was no significant difference in results between patients implanted on their dominant side and patients implanted on their nondominant side. When ears are different according to their peripheral factors, the authors suggest implanting the better ear, provided there is no significant hearing in that ear. When both ears are identical, the side of implantation should be the side of handedness laterality to facilitate device manipulation (a practical reason).
The authors describe the surgical technique and results of the Nucleus device in 50 recipients. Cochlear ossification was present in one third of patients. Total insertion was possible in all cases with a partial ossification (< or = 8 mm), and once in a case with a total ossification (> 8 mm) of the scala tympani of the basal turn. Results were not significatively different in normal cochleas and in ossified cochleas. The authors describe a per-operative algorithm in front of a basal turn ossification, emphasizing on the insertion in scala vestibuli through the oval window. According to the results, the authors prefer the use of a multi-channel cochlear implant than a monochannel implant, even in ossified cochleas.
The contribution of short-latency evoked potentials to the exploration of auditory, visual and somatosensory neurosensory pathways is capital. The determination of short-latency vestibular evoked potentials has encountered many difficulties, mainly due to the necessity to find a specific, very short stimulation in order to select and synchronize the vestibular nerve fibers. Recent studies in animals have demonstrated short-latency potentials evoked by angular accelerations, linear accelerations or electric shocks on the round window. The generators of these potentials seem to be located in the vestibular nerve and nuclei. Electric stimulations of the internal ear have the advantage of providing a study of the peripheral vestibular pathways separately on both sides, while accelerations involve both vestibula, which probably makes the interpretation of data very difficult.
The uptake of two tritiated carbohydrates, D-[3H]-glucosamine and L-[3H]-fucose, to the developing rat cochlea was examined using light and electron microscopic radioautography. Both carbohydrates, administered to in vitro developing rat cochleas, shared a similar ultrastructural labeling pattern on the microvilli and apical cell region and on the tectorial membrane (TM) fibrils. On embryonic day 18, the radiolabeling appeared on the apical surface of the undifferentiated epithelium that will develop into both spiral limbus and Kölliker's organ (KO), while on postnatal day (PD) 1, it was only located on the apical surface of the KO. When D-[3H]-glucosamine was administered in vivo to newborn rats, the radiolabeling was observed in the TM covering the KO at PD 3. Lastly, D-[3H]-glucosamine administered in vivo to PD 7 rats, appeared at PD 9 in the TM region lying just above the organ of Corti. The present findings support the previously suggested leading role of the spiral limbus and KO in the secretion of the TM during cochlear development. The secretion of carbohydrates, and probably of other matrix components, starts on the spiral limbus and KO region and progressively extends to the organ of Corti.
Click-evoked otoacoustic emissions (OAEs) were recorded from both ears in two groups of neonates ranging in age from a few days to two months after birth. The first group consisted of 55 full-term neonates with normal developmental history and health status, including absence of middle ear disease and familial history of hearing loss. The second group consisted of 40 infants admitted to an intensive care baby unit for various pathological conditions (anoxia, prematurity, hyperbilirubinemia, meningitis). The method achieved 97% success in assessing cochlear function in the normal group; it was possible to identify a clear and reproducible response in all ears, except 3, at 70 dB SPL (i.e. approximately 30 dB nHL). The detection-threshold of OAEs was comparable to that measured in adult ears. Several babies from the second group produced no OAEs and were also tested by auditory brainstem responses (ABR): these infants demonstrated ABR thresholds higher than 30 dB nHL. OAEs provide an objective tool for a rapid and effective screening test for cochlear impairment in neonates.
Topical application of FGF (fibroblast growth factor), a potent mitogen for mesodermal and neuroectodermal cells, was given to promote the healing of tympanic membrane perforations in rats. Calibrated tympanic membrane perforations were performed in 30 rats. At day 0, each rat received 40 microliters of placebo in the right ear and 40 microliters of a solution containing FGF in the left ear at different concentrations. The quality of healing was observed by otomiscroscopy and by light microscopic examination of histological sections. The mean time of closure was significantly shorter in ears receiving an amount of 400 ng FGF (6.1 days), as compared to non-treated ears (8.8 days). Using a higher dose of FGF, the promoting effect was counterbalanced by a high rate of myringitis. Using a dose of 200 ng of FGF, no difference was noticed between placebo group and FGF group.
This paper analyzes the main difficulties encountered in cochlear implants in children. Neurophysiological data indicate that cochlear implants should be put during the first 3-4 years of life. The principal controversies concern: the indications of cochlear implants, the type of implant (mono or multichannel), surgical problems, problems of implant set-up, strategy of rehabilitation.
This paper reports our experience about intraoperative facial nerve monitoring carried out in 97 patients operated on by a retrosigmoid approach. Intra-operative facial nerve monitoring was performed using a pneumatic sensor which transforms into acoustic signals contractions of facial muscles elicited by mechanical, electrical or thermal stimulations of facial nerve. Long term results showed that a normal facial function (grade I) was achieved in 90.5% of patients, 4 patients were grade II, 2 patients grade III, a total paralysis (grades V and VI) was persistent in 3 patients. Our experience with facial nerve monitoring suggests a modification of the strategy of dissection based upon a preservation of the arachnoid veil and a medial to lateral direction of dissection.
This paper summarizes the most recent findings dealing with the anatomical development of the human cochlea, and especially with ultrastructural data from both scanning and transmission electron microscopic studies. It also briefly reviews physiological findings and attempts to specify the timing of the main developmental events, i.e. the onset of function, the acquisition of adult properties, and the sensitive periods.
The various techniques of cochlear implantation are described. Implants may be divided into mono- and multi-electrode and into intra- and extra-cochlear. Cochlear implants are indicated only in patients with total or deep bilateral deafness with residual fibres still functioning in the acoustic nerves. Intra-cochlear multi-electrode implants are the most sophisticated ones and usually provide better performances than those observed with mono-electrode implants.
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Otoemissions are acoustic signals emitted by the cochlea in response to a short acoustic stimulation (click) that may be recorded with a miniaturized microphone placed within the external auditory canal. They reflect the active mechanisms of the cochlea as they relate to the contractile properties of the outer hair cells, which determine the cochlear properties of sensitivity to and selectivity of frequencies. We have been studying for 5 years the clinical applications of otoemissions in over 500 patients. Otoemissions in 100% of normal ears may be recorded, and the detection threshold is generally 10 dB lower than the psycho-physiological threshold. In pathology, otoemissions present a practical interest in the following applications: objective investigation of perception hearing loss, early screening of cochlear disease consecutive to administration of ototoxic drugs, or sound-induced trauma; exploration of Meniere's disease; study of modifications induced by osmotic substances; diagnosis of retrocochlear disease; quick objective assessment of cochlear function in the newborn and the child.
Evoked acoustic emissions (EAEs) and spontaneous acoustic emissions (SAEs) recordings hold some promise as a fast, objective and non-invasive audiological procedure, especially in children. However, accurate interpretation in the emission response must be based on the basic properties of the emissions present in a younger age group. In so doing, the properties of emissions were investigated in 49 ears from 26 children, whose ages varied between 2 days and 10 years. EAEs could be recorded in all normal ears, but the incidence of long-duration EAEs decreased with age. There were no statistically significant variations in recording the EAEs detection threshold with age. The incidence of SAEs also decreased with age.
Short-latency potentials evoked by round window electrical stimulation were recorded in guinea pig by means of vertex-pinna skin electrodes using averaging techniques. Constant current shocks of 20 microseconds or 50 microseconds (25-300 microA) were used to evoke both auditory and vestibular brain-stem potentials. Pure auditory potentials, comparable to those evoked by acoustic clicks, were obtained by 20 microseconds electrical stimuli and disappeared during an auditory masking procedure made with a continuous white noise (110 dB SPL). Short latency potentials labeled V1, V2 and V3 were obtained by 50 microseconds electrical stimuli during an auditory masking procedure. This response disappeared after specific vestibular neurectomy, whereas the auditory response evoked by acoustic clicks or by electrical stimulation remained unchanged, suggesting that these latter potentials had a vestibular origin.
Click-evoked otoacoustic emissions were recorded in a group of normally hearing subjects (n = 52 ears) and a group of patients demonstrating several common types of sensorineural hearing loss (n = 85 ears) in order to study the clinical applicability of acoustic emissions. In the normally hearing population, all ears demonstrated acoustic emissions that could be elicited at intensities below the normal subjective threshold for the sequence of clicks (mean, -5.2 dB hearing level [HL]). Sixty-seven percent of the normal ears showed long (greater than 20 ms) click-evoked emissions, and spectral analysis showed a broadband spectral component with several narrowband frequency peaks. In patients with sensorineural hearing loss, the incidence of acoustic emissions decreased and the detection threshold increased linearly with increasing threshold. No emissions were elicited from ears exhibiting subjective click thresholds greater than 35 dB HL. Hearing-impaired ears showed a significantly higher proportion of short duration emissions and a significant reduction in the mean number of narrowband frequency peaks in comparison to the controls. Therefore, acoustic emissions can be used as a reliable technique for objective study of normal micromechanical activity within the cochlea and for detection of subtle changes in cochlear disease. However, they have not been demonstrated to be useful in differentiating cochlear disease.