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Biomedical subjects

A C Coats

Publications and source records attributed to A C Coats.

At least 37 records · Page 2Linked to original sources
PubMed1979

Voluntary nystagmus masquerading as Tullio's Phenomenon.

Nystagmoid eye movements elicited by humming loudly was initially misdiagnosed as Tullio's phenomenon (abnormal acoustical stimulation of the vestibular apparatus owing to labyrinthine fistula). Further workup lead to a final diagnosis of a form of voluntary nystagmus characterized in some reports as "hysterical mystagmus". Some of the characteristics of this example of voluntary nystagmus differed from generally accepted descriptions.

Adult↗
PubMed1979

Normal short-latency electrophysiological filtered click responses recorded from vertex and external auditory meatus.

We recorded normal electrophysiological responses to third-octave filtered clicks from external auditory meatus (EAM) and vertex electrodes referred to coupled earlobe electrodes (forehead ground). From both vertex and EAM, polarity-sensitive responses predominated at low frequencies and exhibited characteristics of both phase-locked neural responses (frequency-following response or FFR) and cochlear microphonics (CM). The FFR-like response predominated at the vertex site and the CM-like response predominated at EAM. At high frequencies, polarity-insensitive responses closely resembled rectangular-pulse click action potentials and brainstem evoked potentials, with clearly defined N1 and V peaks recorded from EAM and vertex, respectively. As frequency was lowered, the N1 and V peak latencies increased, the peaks broadened, and the latency-intensity curves steepened with greater prolongation occurring at lower click intensities. Lowering click frequency also shortened the N1-V interval and caused the plot of N1-V interval versus click intensity to become steeper. Plots of polarity-insensitive response amplitudes and thresholds against frequency revealed a high frequency bias for both N1 and V, but the V "frequency response" was flatter. A possible explanation of the shortened N1-V interval at low click frequencies based on this flatter V "Frequency response" is presented.

Acoustic Impedance Tests↗
PubMed1978

Human auditory nerve action potentials and brain stem evoked responses.

Latency-intensity (L-i) functions for (1) the auditory nerve action potential (AP) N1 peak, (2) the brain stem evoked response (BER) V peak, and (3) the N1-V interval were related to hearing level and lesion location. The AP L-l curves tended to steepen with increasing 4 to 8 kHz hearing level. This relationship was identical for cochlear and retrocochlear ears, except for a few retrocochlear ears with "inappropriate AP perservation." Both high-frequency cochlear loss and retrocochlear abnormality prolonged peak V latency, but retrocochlear abnormality generally prolonged it more. Among cochlear-loss ears, as 4 to 8 kHz hearing levels increased, N1-V intervals decreased and L-i curve slopes increased. In contrast, retrocochlear abnormality greatly prolonged N1-V intervals. As a retrocochlear sign, N1-V prolongation was slightly more reliable than V prolongation.

Action Potentials↗
PubMed1977

Human auditory nerve action potentials and brain stem evoked responses: effects of audiogram shape and lesion location.

Simultaneously recorded auditory nerve action potentials (APs) and brain stem auditory-evoked responses (BSERs) were correlated with audiogram shape and with location of patholgoic condition. High frequency (4 to 8 kHz) hearing loss (1) prolongs AP and BSER latency, (2) shortens the interval between the first AP peak (N1) and the fifth BSER peak (V), and (3) creates relatively large latency differences between condensation and rarefaction responses (thus bringing into question the common practice of combining condensation and rarefaction responses). Ears with retrocochlear deficits in the subjects in the study were detected reliably by prolonged N1 to V interval and increased BSER peak V latency. The reliability of these retrocochlear signs was further increased by allowing for the effects of audiogram shape. Another retrocochlear sign, termed "inappropriate AP preservation," was positive in 40% to 50% of the retrocochlear ears.

Action Potentials↗
PubMed1977

Voluntary nystagmus.

Voluntary nystagmus is a pendular, rapid, conjugate, primarily horizontal, benign nystagmus initiated and maintained by voluntary effort. The amplitude is variable, but always low. The rate is constant and rapid. Convergence is variable--apparently essential in some, nonessential in others, but related in all of our cases. This condition appears to have a familial component and is more common than originally thought. Voluntary nystagmus should be considered when dealing with any patient exhibiting nystagmus in order to minimize the possibility of misdiagnosis as occurred in one of our cases.

Adolescent↗
PubMed1976

The air caloric test. A parametric study.

We studied the normal air caloric response's intensity and variability. Intensities of "preliminary standard" (47 C, 25 C, 60 seconds, 10 liters/min) air and standard bithermal water responses were the same, but the air responses were more variable. Control experiments suggested that the tendency of the air stream to equilibrate toward ambient may account for much of air's relatively high variability. Increasing the air irrigation's duration, flow rate, and separation from body temperature increased response intensity. Air's test-retest variability decreased when flow rate and duration increased and when temperature approached ambient. Therefore, we suggested that irrigating temperatures be chosen as close to ambient as possible and duration and flow rate be made as large as possible. From a table equating air and standard bithermal water responses, we selected tentative clinical air irrigation parameters of 27.5 C, 45.5 C, 100 seconds, and 13 liters/min.

Adolescent↗
PubMed1975

Superior vestibular nerve sectioning. Experimental studies in squirrel monkeys.

Spontaneous, positional, and paroxysmal positional nystagmus were studied before and after sectioning the superior division of the vestibular nerve and the anterior vestibular artery in squirrel monkeys. Histopathologic study of the temporal bones confirmed the degeneration of the macula utriculi with release of statoconia, but failed to identify the released utricular statoconia within the vestibular endolymphatic space in any animal. Postoperatively the animals consistently demonstrated direction-fixed spontaneous nystagmus until the end of the experiment (five months). Positional tests and Dix-Hallpike maneuver occasionally changed the intensity of the spontaneous nystagmus, but never elicited paroxysmal positional nystagmus. Possible reasons for not demonstrating paroxysmal positional nystagmus in the squirrel monkey are as follows: a resorption of statoconia; slight morphological alteration of the sensory epithelia of the posterior cristae; interference of the posterior crista function due to partial collapse of the membranous ampulla; the existence of interspecies difference; or possibly a faulty hypothesis regarding the etiologic mechanism of benign paroxysmal positional vertigo.

Animals↗
PubMed1975

Temporal bone findings in cryptococcal meningitis.

A 19-year-old woman with cryptococcal meningitis died as a result of her disease, in spite of both intravenous and intraventricular administration of amphotericin B. Gross and microscopic examinations revealed multiple cysts containing Cryptococcus neoformans within the central nervous system. Studies of the temporal bones revealed both neural and end organ destruction with the presence of Cryptococcus when stained by Gomori methenamine silver nitrate method. We present the results of audiometric and vestibular examinations. The case history depicts a progressive neurological involvement by Cryptococcus.

Adult↗
PubMed1975

"Saccadic nystagmus" in cerebellar cortical atrophy.

An ocular dyskinesia designated "saccadic nystagmus" was observed in a patient with cerebellar cortical atrophy. Saccadic nystagmus is a sustained ocular dyskinesia present during visual fixation and abolished by eye closure. It is difficult to distinguish visually from either pendular or jerk nystagmus without eye movement recordings. The oscillations are horizontal and rapid and may be influenced by direction of gaze. Caloric nystagmus (eye closed) and optokinetic nystagmus were normal in our patient. Visual fixation abolished caloric nystagmus, which was replaced by saccadic nystagmus.

Caloric Tests↗