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Biomedical subjects

P R Lambert

Publications and source records attributed to P R Lambert.

At least 37 records · Page 2Linked to original sources
PubMed1994

Electric auditory brain-stem responses in nucleus multichannel cochlear implant users.

OBJECTIVE: The electrically elicited auditory brain-stem response (EABR) has been proposed as a tool for use in cochlear implant device setting. To systematically examine the relationships of psychophysical perceptions and EABRs, implant users underwent a series of comparative measurements. The characteristics of the EABR were assessed for their predictive value in determining the subjective measures needed to set the implant device. DESIGN: Characteristics of the EABR and various perceptual measures in a group of cochlear implant users served as compared variables in a correlational study. SETTING: The study was carried out in the audiology clinic of a university hospital. The audiology clinic maintained a fully equipped evoked potential laboratory, and was part of an otolaryngology department that supported a cochlear implant program. SUBJECTS: The subjects consisted of 10 consecutively selected postlinguistically deafened adult multichannel cochlear implant users. MAIN OUTCOME MEASURES: Morphology, latency, and amplitude measures of the EABR recordings were compared with behavioral perceptions of threshold, most comfortable and uncomfortable loudness levels. RESULTS: Perceptual measures of threshold were found to be significantly related to the threshold of the EABR across subjects and electrode position. Simple linear regression analysis was used to measure the degree of the relationship. An r value of 0.89 attests to a significant relationship. The EABR wave latencies and amplitudes were found to have no significant relationship to any of the perceptual measures examined. CONCLUSIONS: Although EABR cannot replace behavioral measurements for device setting, in difficult cases EABR thresholds may be used as a starting point from which to estimate settings for the device.

Adult↗
PubMed1994

Inner ear hair cell regeneration in a mammal: identification of a triggering factor.

Recent observations have shown that mammals possess a limited capacity for regeneration of inner ear sensory epithelia. It is clear, however, that a mitogenic growth factor will be necessary to up-regulate this capacity before clinical application becomes feasible. This study used in vitro cultures of adult mouse vestibular organs for assessing the mitogenic effect of transforming growth factor alpha (TGF-alpha). Sixty-one utricles and cristae were maintained in culture for 7 to 8 days. Neomycin was used to damage the hair cells. Autoradiography permitted identification of any cell which had undergone mitosis during the culture period. The proliferative response was compared in organs exposed to TGF-alpha and those maintained in the basic culture medium only. The results demonstrated that TGF-alpha significantly increased cell proliferation in the sensory epithelia and also in the marginal zones surrounding them. This finding provides a scientific basis for the concept that inner ear hair cell damage in humans may someday be reversible pharmacologically.

Animals↗
PubMed1993

Regenerative proliferation in inner ear sensory epithelia from adult guinea pigs and humans.

Supporting cells in the vestibular sensory epithelia from the ears of mature guinea pigs and adult humans proliferate in vitro after treatments with aminoglycoside antibiotics that cause sensory hair cells to die. After 4 weeks in culture, the epithelia contained new cells with some characteristics of immature hair cells. These findings are in contrast to expectations based on previous studies, which had suggested that hair cell loss is irreversible in mammals. The loss of hair cells is responsible for hearing and balance deficits that affect millions of people.

Adult↗
PubMed1992

Primary lymphoma of the temporal bone.

Involvement of the temporal bone by lymphoreticular neoplasm is rare; all reported cases have been of secondary involvement. This article presents what we believe to be the first two reported cases of primary temporal bone lymphoma. The patients, an elderly man and a boy, both presented with infection of the ear, hearing loss, and facial nerve paresis. In both cases, facial paresis resolved after appropriate chemotherapeutic treatment. Patient presentation and clinical course are discussed in light of published work on temporal bone malignancy. Further investigation, including computed tomography and biopsy, should be considered for patients who present with an apparent middle ear infection unresponsive to medical therapy. The development of facial paralysis in such a patient warrants heightened suspicion of malignancy.

Aged↗
PubMed1992

Promontory electrical stimulation in postoperative acoustic tumor patients.

Complete deafness can follow acoustic tumor surgery and results from labyrinthine injury, auditory nerve trauma, and/or vascular compromise. A central auditory prosthesis is one potential rehabilitative strategy in such patients. Anatomical studies suggest that some spiral ganglion cells may survive after vascular occlusion, and we have demonstrated responses to electrical stimulation in patients after labyrinthectomy. It was thus hypothesized that patients deafened after a hearing conservation attempt, but maintaining an intact auditory nerve, could utilize an intracochlear implant. To investigate this possibility, promontory electrical stimulation was performed on three patients who had tumors less than 2 cm and who had serviceable preoperative hearing, but no responses postoperatively. Behavioral responses and electrically evoked auditory brainstem and middle latency responses were obtained from two patients, one of whom was 6 years postsurgery. These data indicate that a cochlear implant may be possible after acoustic tumor surgery.

Adult↗
PubMed1991

Multichannel cochlear implant and electrically evoked auditory brainstem responses in a child with labyrinthitis ossificans.

Ossification of the cochlea following meningitis presents a surgical challenge. Electrode mapping, especially in the young child, is difficult given the uncertainty of electrode contact with viable neural elements. This paper reviews surgical technique and the use of auditory brainstem responses to map the electrodes. A 4-year-old child deafened by meningitis at age 20 months had bilateral cochlear ossification by computed tomography. At surgery, a canal wall-down mastoidectomy and closure of the ear canal were performed. A trough around the modiolus was drilled, and the electrode array was placed in it. Post-operatively, the patient gave aversive or no responses to electrode stimulation. To assess electrode function, auditory brainstem responses to individual electrode activation were obtained under general anesthesia. Functioning electrodes could thus be selected for mapping. The patient now responds well to sound.

Child, Preschool↗
PubMed1991

Auditory evoked potentials.

Auditory evoked potentials (AEPs) have become an integral part of the current otologic/audiologic test battery. With these techniques, synchronous neural activity can be examined from the peripheral end organ of hearing up to the cortical structures responsible for audition. The clinical applications of AEPs range from their use as an indicator of auditory sensitivity in patients who either cannot or will not respond in a conventional behavioral test situation to their use in the diagnosis and monitoring of various otologic and neurologic disorders. As such, measurement of AEPs allows the clinician a unique glimpse of the auditory system.

Audiometry, Evoked Response↗
PubMed1990

Promontory electrical stimulation in labyrinthectomized ears.

Bilateral deafness can occur in patients with Menière's disease who have undergone a labyrinthectomy in one ear. To investigate the feasibility of a cochlear implant in the labyrinthectomized ear, promontory electrical testing by transtympanic needle was performed in six patients who had undergone a unilateral transmastoid labyrinthectomy 6 weeks to 5 years previously. All patients had a behavioral response to the stimulus, and each described a different pitch percept with the four frequencies used. Five of the patients demonstrated an electrically evoked middle latency response. These data are comparable with behavioral and electrophysiologic responses from ears deafened by other causes and now successfully implanted. The results suggest that peripheral neural elements and central auditory pathways remain at least partially functional many years after a labyrinthectomy. Thus, a labyrinthectomy should not be withheld as a surgical option if otherwise indicated.

Adult↗
PubMed1990

Trends in rehabilitation after cochlear implantation.

Although postimplant rehabilitation is generally considered to be an important aspect of a cochlear implant program, the literature reports widely varying practices in the implementation of such programs. The National Institutes of Health consensus statement on cochlear implantation (May 1988), while recognizing that aural rehabilitation facilitates maximal use of the implant, offers no specific guidelines or recommendations. A questionnaire survey was made of over 200 otolaryngologists to determine current practices in a variety of aspects of their cochlear implant programs. Results were obtained from a total of more than 1400 patients, including adults, adolescents, and children. Rehabilitation is an integral part of the cochlear implant program in the vast majority of active programs surveyed. General aspects of cochlear implant programs, as well as those of rehabilitation programs in particular, are discussed.

Adolescent↗
PubMed1990

Congenital absence of the oval window.

From 1983 to 1987, seven patients with conductive hearing loss were found to have congenital absence of the oval window. Six of these patients underwent vestibulotomies and reconstruction with House wires or total ossicular reconstruction prostheses. Surgical findings included absent or rudimentary stapes in all cases, abnormal facial nerves in four cases, and abnormal long processes of the incus in four cases. All patients had normal external ear canals and tympanic membranes. Hearing initially improved 20 to 45 dB in four of the six patients reconstructed. Over time, however, much of this initial hearing gain was lost. A marked difference in hearing results was evident between this series of absent oval window cases and a recent series of major atresia cases.

Adolescent↗
PubMed1990

Use of the bone conduction ABR Wave I response in determination of cochlear reserve.

Interest in bone-conducted stimulus auditory brainstem response (BC-ABR) testing has centered around evaluation of cochlear integrity in neonates and in patients who are difficult to evaluate audiometrically. The present study was designed to evaluate the Wave I component of the BC-ABR and to determine the utility of this response in assessment of cochlear reserve. The source of Wave I has been shown to be the distal eighth nerve. It was postulated that the presence or absence of this component would provide ear specific information useful for determination of cochlear integrity. In order to test this hypothesis, patients with a documented unilateral hearing loss were studied. Stimulus presentation was via the Radioear B-70 bone vibrator used in conventional audiometric assessment. Evoked potential responses were recorded at four presentation levels. Subjects had either normal hearing bilaterally or normal hearing in one ear and a mild-to-profound sensorineural hearing loss in the opposite ear. Our data indicate that the Wave I response, when measured in this fashion, is ear specific. Ear specificity was shown to be aided by good waveform morphology, as typically observed in younger subjects, and by a relatively large discrepancy in hearing thresholds between the normal and hearing-impaired ears. This technique may be of value in determination of cochlear reserve in patients with problematic masking dilemmas.

Adult↗
PubMed1989

Comparison of tympanic membrane to promontory electrode recordings of electrocochleographic responses in patients with Menière's disease.

The purpose of the present study was to evaluate ECoG recordings obtained simultaneously from a transtympanic electrode and a tympanic membrane electrode in 26 patients with unilateral Meniere's disease. The ECoG recordings were examined quantitatively with regard to absolute amplitude of the summating potential and action potential. Recordings were examined qualitatively in terms of overall waveform quality and ease of component wave identification. All patients demonstrated a clear response with both electrodes. Although the transtympanic electrode resulted in the most robust responses in overall amplitude, the tympanic membrane electrode provided recordings equal to or, in most cases, superior to other noninvasive, extratympanic methods currently available. Furthermore, in our patient population, the likelihood of a positive (upward-going) summating potential was less for the tympanic membrane electrode recordings than for the TT electrode recordings. The major advantages of the TM electrode system are its unique method of stimulus delivery and its ease of application.

Adult↗
PubMed1988

Simultaneous recording of noninvasive ECoG and ABR for use in intraoperative monitoring.

Monitoring auditory evoked potentials, especially surface recorded responses (ABR), during neuro-otologic surgery is being widely used. Recording of the most peripheral components of the ABR with surface electrodes can be difficult, however, in patients with hearing loss. To enhance wave I, a newly designed canal electrode for noninvasive electrocochleography (ECoG) has been used. A small reticulated foam plug is inserted in the ear canal and serves as the electrode. The signal is transduced through a center polyethylene tube. The advantages of this system for ECoG are several: (1) simplified signal presentation, obviating the need for custom ear mold or button transducer; (2) large electrode surface area that lowers impedance and improves signal to noise ratio; and (3) stability of the electrode during manipulations within the surgical field. There are several advantages to supplementing ABR with simultaneous ECoG. First, there is a significant enhancement in wave I amplitude, an important factor when monitoring from hearing impaired patients in an operating room environment. Ability to clearly define wave I permits use of the I-V interwave interval, which can be a more sensitive parameter than wave V latency alone. Secondly, more rapid feedback on changes in cochlear function is available since, compared to surface recordings alone, fewer responses need to be averaged.

Audiometry, Evoked Response↗
PubMed1988

Electrocochleography: methods and clinical applications.

The use of electrocochleography (ECoG) as a tool in the diagnosis, assessment, and monitoring of certain neuro-otologic disorders has attracted renewed attention in the United States. The use of ECoG among otologists and audiologists has increased in recent years, primarily due to the availability of relatively easily applied, noninvasive extratympanic electrodes. Information derived from ECoG recordings has been shown to be helpful in the objective identification and monitoring of Meniere's disease and endolymphatic hydrops. In addition, ECoG may be used to enhance our ability to observe the most peripheral component of the auditory brain stem response (Wave I) for routine clinical assessment or during intraoperative monitoring procedures in which certain structures of the ear are at risk for permanent damage. This article provides an overview of current techniques and clinical applications of ECoG.

Audiometry, Evoked Response↗
PubMed1987

Light microscopic evidence of hair cell regeneration after gentamicin toxicity in chick cochlea.

This study examines the temporal pattern of hair cell loss in the chick basilar papilla following ten days of gentamicin administration in hatchling chicks. Chicks were subsequently killed at ages 11, 18, 25, and 32 days. The basilar papillae were embedded in plastic and serially sectioned for light microscopic analysis. Hair cell counts were obtained at 100-microM intervals throughout the length of the papilla. Significant hair cell loss was documented basally in the 11-day-old chicks, and spread apically over time to maximal loss in the 18-day-old animals. Relative to the control chicks, there was a 36% hair cell loss in these animals. Interestingly, there appears to be a progressive partial recovery of the normal hair cell counts in the 25- and 32-day-old animals.

Animals↗