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Biomedical subjects

C A Mangham

Publications and source records attributed to C A Mangham.

27 records · Page 2Linked to original sources
PubMed1983

Evaluation of tensor tympani muscle dominance in the biphasic acoustic reflex.

The Acoustic reflex frequently causes a biphasic change in impedance at onset. Understanding the cause of the biphasic response is important for establishing a physiological basis for the clinical measurement of reflex latency. The decrease in impedance at onset may be due to uncoupling of impedance contributed by the cochlea. Subsequent increases in impedance predominantly reflect stapedius muscle activity. The clinical implications of this physiologic model are discussed.

Acoustic Impedance Tests↗
PubMed1981

Management of intratemporal vascular tumors.

Vascular tumors (vascular malformations and hemangiomas) of the temporal bone are uncommon, and guidelines for their management have not been published. In an effort to develop an approach to their management, the present study examined the pathological, clinical, and surgical experience with ten of these lesions treated at the Otologic Medical Group, Inc., and St. Vincent Medical Center in Los Angeles from 1960 to 1980. Intratemporal vascular tumors occurred most frequently at two sites, the internal auditory canal and the geniculate ganglion. Histological features and clinical behavior did not correlate. Both vascular malformations and hemangiomata invaded the facial nerve. Surgical excision in these cases required severence and repair of the involved facial nerve. Complete surgical excision is the treatment of choice of vascular lesions of the temporal bone.

Adult↗
PubMed1980

Stapedius reflex quantification in acoustic tumor patients.

This investigation is a human application of previously reported work from our laboratories on experimental acoustic tumor effects on the stapedius reflex in monkeys. In this study, the contralateral stapedius reflex was elicited in human controls and in subjects with an acoustic tumor. Acoustic impedance was recorded on magnetic tape for offline analysis of reflex threshold, latency, rise, amplitude, decay, and relaxation. Typical tumor effects on threshold and decay were observed. Most important was the demonstration that decay measured at 20 db SL was more sensitive and more specific for tumor than decay measured at the conventional 10 db SL. Stapedius reflex latency, rise, and amplitude were more sensitive to the presence of a tumor than were measures of threshold and decay. These data indicate that qualification of the reflex will increase the utility of the test.

Acoustic Impedance Tests↗
PubMed1980

The negative acoustic reflex in retrocochlear disorders.

The most frequent impedance abnormality of an acoustic tumor is an absent reflex. However, this finding also occurs with middle ear disorders and is therefore nonspecific. This study recorded the contralateral acoustic reflex of human subjects suspected of having an acoustic tumor. Many tumor subjects, by visual inspection of the impedance bridge balance meter, appeared to have an absent reflex. Most of these subjects, in fact, had small amplitude negative reflexes by offline analysis on an averaging computer. Recognition of these negative reflexes increases the specificity and sensitivity of the reflex test for acoustic tumors. We recommend reflex testing with averaging computer monitoring to ensure their recognition.

Acoustic Impedance Tests↗
PubMed1979

A case for further quantification of the stapedius reflex.

Clinical stapedius reflex determinations presently include only threshold and decay measurements. Recent observations indicate that reflex latency, amplitude, and rise and relaxation times are sensitive to cochlear and brain stem disorders. Our investigations using a chronic animal model of an experimental acoustic tumor show that reflex amplitude, latency, and rise time are exquisitely sensitive to extrinsic pressure on the auditory nerve. Because of our observations and those of others, we suggest that further quantification of the reflex test will increase its sensitivity and reliability. Quantification can be achieved by an interface between an impedance bridge and a small computer to provide on-line averaged values for each reflex parameter.

Acoustic Impedance Tests↗