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Biomedical subjects

R A Ruth

Publications and source records attributed to R A Ruth.

At least 19 recordsLinked to original sources
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

Trends in electrocochleography.

Currently there appears to be a resurgence of interest in the measurement of the peripheral-most electrical potentials of the auditory system. These measurements, known collectively as electrocochleography, may be used (1) to assess and monitor patients with Meniere's disease or endolymphatic hydrops, (2) to enhance wave I of the surface recorded ABR, and (3) as a means of monitoring the peripheral auditory structures during surgery. Various recording techniques and electrode types are reviewed and suggestions are provided for response interpretation in several patient populations.

Acoustic Stimulation↗
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↗
PubMed1988

Use of disposable ear canal electrodes in auditory brainstem response testing.

In this study a disposable ear canal electrode and stimulus delivery system (the Enhancer l) was evaluated for its clinical utility and the observed enhancement of the auditory brainstem response Wave I with its use. Data were collected from normally and abnormally hearing subjects, with both the conventional forehead-to-mastoid electrode array and the forehead-to-ear canal electrode arrangement provided by the Enhancer I ear canal electrode setup. For the normally hearing group, simultaneous acquisition of forehead-to-ipsilateral ear canal and forehead-to-ipsilateral mastoid electrode linkages was obtained. For the abnormally hearing subjects, a comparison was made between the Enhancer I system and the conventional forehead-to-mastoid electrode configuration used with a TDH-49 transducer for click delivery. Our findings indicate that Wave I was enhanced substantially when using the disposable ear canal electrode compared with the more conventional forehead-to-mastoid electrode configuration for both normally and abnormally hearing subjects. The Enhancer I electrode evaluated in this study proved to be painless for the subjects and extremely easy to use, requiring no more time in subject preparation than the more common surface recording electrode application.

Adult↗
PubMed1987

Meningitis and facial paresis. Implications for cochlear implantation.

Most postlingually deafened individuals receive auditory sensations with a cochlear implant. We describe a postmeningitic patient with bilateral facial paresis who failed to be stimulated with a multichannel device. In light of the facial dysfunction, primary auditory nerve damage by meningitis is postulated as the cause of implant failure. Preoperation electrical stimulation of the cochlea using an alternating current signal is recommended as a means of assessing cochlear implant candidacy.

Cochlear Implants↗
PubMed1985

Brain-stem auditory-evoked potentials during lidocaine infusion in humans.

Auditory brain-stem responses (ABR) were recorded in six healthy male volunteers during intravenous infusion of lidocaine that achieved systemic blood levels similar to those seen with conduction anesthesia and antiarrhythmic therapy. Following an initial loading dose of lidocaine (1 mg/kg), subjects noted prominent tinnitus, perioral numbness, and drowsiness. All of these symptoms except drowsiness abated during continued infusion as blood concentrations reached equilibrium. All subjects noted that the click stimuli used to elicit ABR varied markedly in intensity and character throughout the lidocaine infusion. Although waves I and III were unaffected by lidocaine, wave V exhibited significant decreases in amplitude and increases in latency. Therefore, the more central components of the auditory system seem to be the prominent site of lidocaine's central nervous system effects.

Acoustic Stimulation↗
PubMed1979

Audiometric evaluation of noise induced hearing loss.

Audiometric evaluation in conjunction with other components of the hearing conservation program serves to minimize the potential hazard of noise related hearing loss. Success of the industrial hearing conservation program rests in large measure with the implementation of competent audiometric testing procedures. Thus, consideration must be given to certain critical factors necessary for measurement of hearing sensitivity, such as the qualifications of the examiner, monitoring schedules, test environment, instrumentation, method of testing, recording of results, interpretation of test findings, and appropriate referral criteria.

Audiometry↗
PubMed1977

Prediction of hearing sensitivity from acoustic reflexes in mentally retarded persons.

The ability of the sensitivity prediction from acoustic reflex (SPAR) technique to estimate hearing loss in mentally retarded subjects was investigated by comparing measured pure-tone thresholds determined through tangible-reinforcement operant-conditioning audiometry with predicted sensitivity from the SPAR procedure. Measurements were completed on a total of 32 retarded individuals having hearing levels ranging from normal to profound hearing loss. With minor exception, absences of the acoustic reflex were always accompanied by clearly abnormal tympanometry findings in the probe ear; therefore, the problem of unexplained absences of the reflex appeared to be minimal. Hearing loss never was present in those subjects for which SPAR predicted normal hearing, and the SPAR procedure never failed to detect an existing sensorineural hearing loss. On the other hand, there was some tendency for hearing loss to be predicted in normal-hearing subjects and for extent of hearing loss to be overestimated in subjects having a hearing loss.

Adolescent↗