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Biomedical subjects

C G Fowler

Publications and source records attributed to C G Fowler.

66 records · Page 4Linked to original sources
PubMed1985

Frequency dependence of the binaural interaction component of the auditory brainstem response.

The frequency dependence of the binaural interaction component of the auditory brainstem response was examined. Subjects included 24 with normal hearing and 5 with severe high-frequency losses. Tone pips of 100 and 80 dB pe SPL at 1 000 and 4 000 Hz were presented monaurally and binaurally. The binaural interaction component was derived by subtracting the binaural response from the addition of the left and right monaural responses. The binaural interaction component was produced by both 1 000 and 4 000 Hz, although it was larger and more reliable with 1 000 Hz. The absence of responses to 4 000 Hz in cochlear-impaired subjects did not alter appreciably the morphology of the binaural interaction component to 1 000 Hz. The correspondence between the binaural interaction component and the masking level difference was not good.

Adult↗
PubMed1984

Fibrescope urethrocystoscopy.

Cystourethroscopy with a small calibre flexible fibrescope may be performed under topical lignocaine anaesthesia with less discomfort to the patient than with a conventional rigid cystoscope. The method is safe and reliable. The technique is especially useful in out-patient surveillance of bladder cancer.

Anesthesia, Local↗
PubMed1984

Practical experience with flexible fibrescope cystoscopy in out-patients.

Four hundred and seventy-four patients were examined by flexible cystoscopy under topical urethral anaesthesia in the out-patient clinic in the first year after the technique was introduced as the routine method for diagnostic cystoscopy. The technique has proved safe, efficient and highly cost-effective.

Cystoscopes↗
PubMed1984

Fibrescopes in urology.

Innovations in fibrescope design have coincided with a renewed interest in endoscopy of the upper reaches of the urinary tract. This may result in changes in the investigation and treatment of some renal diseases.

Cystoscopes↗
PubMed1983

Effects of stimulus repetition rate and frequency on the auditory brainstem response in normal cochlear-impaired, and VIII nerve/brainstem-impaired subjects.

The effects of signal repetition rate and frequency on the auditory brainstem responses of normal listeners, of persons with cochlear lesions, and of persons with VIII nerve/brainstem lesions were evaluated. The normal group exhibited more waves I and II than did the cochlear and VIII/brainstem groups. The normal and cochlear groups exhibited more waves III and V than did the VIII nerve/brainstem group. The latency of wave I was not different among groups, whereas wave V was significantly later in the VIII nerve/brainstem group than in the other groups. Waves I, III, and V were later for 50/s than for 10/s. Waves I and III displayed shorter latencies for 4000 Hz than for 2000 Hz, whereas wave V displayed similar latencies for the two stimuli. In conclusion, cochlear pathology (less than or equal to 65 dB HL) does not prolong the latencies of waves I and V. A dual mechanism is discussed to explain the rate-dependent latency shift of wave V.

Adult↗
PubMed1983

The impact of optical urethrotomy on the management of urethral strictures.

The introduction of optical urethrotomy by Sachse has reduced the need for urethroplasty: 261 urethroplasties were performed between 1964 and 1983, of which 87 were performed in one stage on patients who would today have undergone urethrotomy as the procedure of first choice. The results in this group are compared with those in 151 patients treated between 1978 and 1983 by 265 internal optical urethrotomies. At 5 years 50% of those treated by urethrotomy needed no further treatment, compared with 83% of those treated by urethroplasty. Nevertheless, the ease and safety of urethrotomy makes it the procedure of first choice, and urethoroplasty should be reserved either for cases where urethrotomy is unsuitable or where it has been tried on several occasions without success.

Adolescent↗
PubMed1982

Brain stem auditory evoked potentials: applications in clinical audiology.

The brain stem auditory evoked potentials (BAEP) or, more appropriately, the auditory brain stem response (ABR) is a series of 5-7, vertex-positive, time-locked electric events. They are usually aroused by a brief, rapid onset, high intensity acoustic click or tonal pip. The vertex positive nature of the events is dictated by the placement of surface electrodes, usually featuring an active electrode on the vertex, a referent electrode on the mastoid or earlobe ipsilateral to the signal source, and a ground electrode on the forehead or other neutral tissue. The size of the ABR is sufficiently small, often fractions of a microvolt, to require the use of many signal presentations (1000-2000 stimuli) and digital averaging of the resulting electrical activity for the stimulus time-locked potentials to be elicited from other physiologic "noise." Since the auditory brain stem potentials are known to be elicitable near a subject's behavioral threshold for the stimulus used, and since the various potentials are thought to originate from different points in the brain stem, they have proved useful in hearing evaluations of human beings for two purposes: a) they are useful as a means of measuring hearing sensitivity from patients who cannot or will not give accurate voluntary responses; and b) they are useful as a diagnostic tool for determining the probable cause of an auditory disorder.

Brain Stem↗
PubMed1976

Deafness and vitiligo.

Seven cases of congenital deafness and an autosomal recessive pedigree pattern were observed in an inbred kindred. Three of the cases also had vitiligo, and there were 2 other cases of vitiligo in this kindred. The vitiligo also appeared to have an autosomal recessive inheritance pattern.

Deafness↗
PubMedDate not supplied

Effects of noise bandwidth on the late-potential masking level difference.

The masking level difference (MLD) is a psychoacoustic phenomenon derived from the subtraction of S pi No thresholds (signals pi radians out of phase and noise in phase at the two ears) from SoNo thresholds (signals and noise in phase at the two ears). The purpose of this study was to determine if the MLD derived from the late components (P1, N1, P2, N2) of the auditory evoked potentials was a physiological correlate of the behavioral MLD. Subjects were 15 young adults with normal hearing. Comparisons were made between behavioral and late potential thresholds to 500 Hz stimuli in So and S pi conditions in quiet, and to 500 Hz stimuli in SoNo and S pi No conditions in narrow band (50 Hz) and wide band (600 Hz) noise. No significant differences were seen for behavioral or late-potential thresholds to So and S pi conditions. The S pi No thresholds was significantly lower than the SoNo threshold, yielding an MLD for both the behavioral and physiological responses. The magnitudes of both the behavioral and late-potential MLD were larger with the narrow band noise than with the wide band noise. Evidence, therefore, is provided that the late-potential MLD reflects similar processes as are responsible for the behavioral MLD.

Acoustic Stimulation↗
PubMedDate not supplied

Adaptation of the acoustic reflex.

Acoustic reflex adaptation is reviewed in normal and abnormal auditory systems. The measurement variables affecting the acoustic reflex threshold are discussed with reference to the intensity level above reflex threshold at which the adaptation is measured. The effects of the activator frequency and activator intensity level on the time course of normal reflex adaptation are reviewed. The diagnostic application of acoustic reflex adaptation is discussed with reference to the different definitions of abnormality found in the literature. The acoustic reflex patterns, including absence, threshold, and adaptation of the reflex, are reported in patients with different degrees of hearing loss, in order to identify the false-positive rates associated with cochlear hearing losses. Finally, the diagnostic accuracy of acoustic reflexes is discussed in subjects having lesions of the CNVIII, brain stem, CNVII, and neuromuscular systems. In summary, a method is advocated for measuring acoustic reflex adaptation over 10 seconds, which allows analysis at both 5 and 10 seconds. Further research is needed on procedural variables including activator intensity level and ipsilateral recording methods, which may increase the diagnostic accuracy of acoustic reflex adaptation.

Adaptation, Physiological↗
PubMedDate not supplied

Aging and middle ear function in rhesus monkeys (Macaca mulatta).

This study provided tympanometric data on rhesus monkeys (Macaca mulatta) and more support for this monkey as a good model for human peripheral auditory function. There have been few published reports concerning middle ear function in rhesus monkeys, and these experiments addressed that need. In the first experiment, peak acoustic admittance (Ytm) and ear-canal volume (Vea) were measured in 17 older adult monkeys and 16 younger adult monkeys. In the second experiment, middle ear resonance frequency was measured in eight younger adult monkeys and four older adult monkeys. Overall, peak Ytm, Vea, and resonance frequency were similar for monkeys and humans. Specifically, peak mean Ytm and mean Vea in monkeys were comparable to those values in human children. There was a trend for older monkeys to have decreased peak Ytm and Vea, but these trends did not reach statistical significance. There was a significant sex effect similar to what has been reported in humans. Male monkeys had larger peak Ytm values and larger Vea values compared with female monkeys regardless of age. Finally, there were no significant age or sex effects on resonance frequency.

Aging↗