Biomedical subjects

C R Morehouse

Publications and source records attributed to C R Morehouse.

6 recordsLinked to original sources

PubMed1998

Antiviral therapy in a child with pediatric human immunodeficiency virus (HIV): case study of audiologic findings.

Over the past decade, much research has been conducted to determine the auditory consequences of human immunodeficiency virus (HIV) infection and acquired immune deficiency syndrome (AIDS). This research, primarily using adult patients, has focused on the involvement of the central auditory nervous system (CANS). Measures of auditory evoked potentials, particularly the auditory brainstem response (ABR), can document changes in the CANS as the disease progresses and during treatment with antiviral therapies such as zidovudine (AZT) and didanosine (ddI). This case study presents the audiologic findings for a child with HIV infection. Evaluations were performed over a 2-year period prior to the initiation of antiviral therapy and following treatment. Audiologic measures included behavioral audiometry, tympanometry, otoacoustic emissions, and ABR latency/intensity functions and rate studies. Findings indicated a gradual shortening of all ABR component latencies following the initiation of antiviral therapy. In addition, a high-frequency hearing loss was detected during the final evaluation subsequent to 19 months of treatment with AZT and ddI.

Anti-HIV Agents↗

PubMed1997

Validity of the ipsilateral acoustic reflex as a screening parameter.

Historically, the ipsilateral acoustic reflex (IAR) has played a prominent role in middle ear screening protocols. However, in 1990, the American Speech-Language-Hearing Association's revised guidelines, "Screening for Hearing Impairment and Middle Ear Disorders," deleted the IAR as a screening parameter. This decision was based on studies that demonstrated that the inclusion of the IAR resulted in a high false-positive rate without adding to the hit rate and thus was a major contributor to over-referral. However, other investigations demonstrated the converse, that the IAR is a sensitive and contributory measure in a screening protocol. Our data suggest that the conflicting results are due to different operating systems in the middle ear analyzers that were used to elicit the IAR. Based on our findings, an optimal IAR screening protocol would use a pulsed elicitation immittance system (multiplexing circuit) and a maximum intensity level of 105 dB HL. Further, if the IAR screening were to be carried out using an automated (programmed) immittance system with an equivalent volume change criteria for IAR detection, the equivalent volume change of > or = 0.03 ml is recommended.

Adolescent↗

PubMed1991

Derived guinea pig compound VIIIth nerve action potentials to continuous pure tones.

A technique is described which verifies neural activity to a very faint continuous sine wave through subtraction of two different far-field whole nerve action potentials from one another. A brief transient is presented to an animal in order to elicit a supra-threshold action potential. The technique is then repeated, but on the second trial a near-threshold sine wave is mixed with the transient and another action potential is collected. The resultant evoked is then subtracted from the evoked potential generated by the transient alone and a small but persistent difference potential is acquired that presumably represents the unit activity occupied by the continuous sine wave. Four experiments are presented to show the validity of this technique, along with a surprising stability of the derived-response latency despite a 30 dB range of the probes. The technique may have promise in predicting behavioral responses to sinusoids acquired from individual animals.

Acoustic Stimulation↗

PubMed1991

Objective auditory threshold estimation using sine-wave derived responses.

A derived response method of acquiring frequency specific auditory evoked potentials that utilizes a pure tone in combination with a toneburst is applied to the measurement of hearing sensitivity in guinea pigs, chinchillas and pocket gophers. Two experiments which demonstrate that thresholds acquired via tone-derived responses are 10 to 15 dB more sensitive than thresholds to solitary tonebursts are described. The derived potentials approximate behaviorally acquired thresholds at frequencies of 0.5 kHz and above. This technique may provide a more rapid means of assessing hearing sensitivity in laboratory animals than by behavioral means.

Acoustic Stimulation↗

PubMedDate not supplied

Strategies for infant auditory brain stem response assessment.

The use of auditory brain stem response (ABR) represents a new dimension in auditory and neurological pediatric assessment. Because the ABR may be altered by stimulus and procedural variables, the lack of an established standard has reduced its clinical efficiency. This paper describes a suggested ABR protocol for infants. Included are stimulus and electrode considerations, measurement criteria, and procedures. In addition, ABR results are presented from 125 newborns ranging between 40 and 49 weeks gestational age. The effects of age and intensity on latency and amplitude are discussed.

Audiometry↗

PubMedDate not supplied

A comparison of auditory brain stem response and behavioral screening in high risk and normal newborn infants.

A total of 345 newborn infants received a behavioral screening consistent with protocol adopted by the Joint Committee on Infant Hearing. Infants were divided into three groups consisting of 108 at-risk for hearing loss, 80 intensive care nursery graduates, and 157 normal control infants. Of the total, 315 newborns received auditory brain stem response (ABR) assessment. The results suggest that 4% of the high risk population had irreversible hearing loss to such a degree that amplification was warranted. Discussion focuses on the questionable use of behavioral screening in the newborn nursery and the application of ABR in a high risk population.

Arousal↗