Central deafness: fact or fiction?

Although there has been some skepticism about the existence of central hearing loss because of the absence of an acceptable tool for its evaluation, techniques are now available for its measurement. There are some excellent behavioral methods available [1]. However, with judicious use of ABR, electrocochleography, and transcranially and ipsilaterally elicited middle-ear muscle reflexes, certain forms of central dysfunction can be studied physiologically.

Disposition of acetaminophen in milk, saliva, and plasma of lactating women.

Acetaminophen (APAP) is a widely used analgesic and antipyretic, but its disposition in human milk has not yet been reported. Twelve nursing mothers (nursing two to 22 months) were given a single 650-mg peroral dose of APAP. Simultaneous saliva and milk samples were collected at zero, 1/4, 1/2, 3/4, 1, 2, 3, 5, 8, 12, and 24 hours after maternal dosing.

Amplification in sudden deafness: a case study.

This report describes a case of traumatic sudden deafness in an adult and the unanticipated clinical problems in providing appropriate amplification and aural rehabilitation. The effect of acoustic distortion on central visual perceptual processes and previously ingrained aural language patterns is presented as a viable explanation. Implications regarding the necessity of evaluating the interaction between the auditory and visual channels are discussed.

Disposition of salicylazosulfapyridine (Azulfidine) and metabolites in human breast milk.

A nursing mother with ulcerative colitis was treated with salicylazosulfapyridine (SASP, Azulfidine). Multiple milk samples were collected over a 2-month period. Maternal plasma, saliva, urine and nursing infant's urine were collected.

Guillain-Barré syndrome associated with Epstein-Barr virus in a cytomegalovirus-negative patient.

Epstein-Barr virus and cytomegalovirus have both been associated with Guillain-Barré syndrome after antibody investigations in several patients. In the teenage female patient in this present report, Guillain-Barré syndrome following infectious mononucleosis was associated with sero-conversion against Epstein-Barr virus but not cytomegalovirus. The findings are consistent with the hypothesis that Epstein-Barr virus might be an etiological agent for the Guillain-Barré syndrome and that infection with cytomegalovirus is not a requisite for the syndrome.

Influence of otitis media on hearing and development.

Otitis media affects nearly every child at some time; many children have mild-to-moderate hearing losses for prolonged periods. The effects of these losses on language and educational development may be significant; possible mechanisms are discussed. Especially in suboptimal listening situations, speech perception may be impaired by even a mild hearing loss.

Binaural interaction in brainstem-evoked responses.

Binaural interaction (BI) in brainstem-auditory-evoked responses (BSERs) was defined as any deviation from the predictions of a model that assumes two independent monaural BSER generators whose outputs are additive. Brainstem-auditory-evoked responses were recorded in response to right (R) monaural, left (L) monaural, and binaural click stimuli. The monaural BSERs were added to give the model's prediction (P) of binaurally evoked BSER (P = L + R), and this trace was then subtracted from the actual binaurally evoked response (B).

Changes in human eighth nerve action potential as a function of stimulation rate.

The primary clinical utility of electrocochleography at the Louisiana State University Medical Center is the detection of hearing losses in children. This frequently requires the administration of a general anesthetic. Time required for this procedure could be shortened if stimuli were presented at a more rapid rate than the customary 10/s, provided the response amplitude is not significantly diminished by adaptation.

Bone-conduction electrocochleography: clinical applications.

Cases are presented which show the clinical utility of recording an electrocochleographic response to bone-conducted stimuli. The procedure is fraught with problems of acoustic control and artifact generation, but has distinct although limited values in clarifying masking dilemmas in patients with bilateral hearing loss.

Superior ultra-audiometric hearing: a new type of hearing loss which correlates highly with unusually good speech in the "profoundly deaf".

This paper reports 42 severely-to-profoundly deaf subjects, 6 of whom have better hearing in the range of 8 to 14 kHz than below 8 kHz. Data on speech capabilities in these six subjects suggest that this ultra-audiometric range may contribute to their speech comprehension and control.

New developments in evaluating central auditory mechanisms.

Five tests are reviewed for their ability to assist in the evaluation of the central auditory mechanism. These are: 1) the Masking Level Difference (MLD); 2) ipsilaterally and contralaterally evoked stapedius muscle reflex; 3) electrocochleography; 4) early brain stem responses; and 5) dichotic listening. A summary chart outlining the tests most commonly in use and their areas of special productivity is also presented.

Electrocochleography in children. A retrospective study.

A follow-up study of 35 children subjected to electrocochleography (Ecog) was conducted to determine (1) agreement of Ecog results with other audiometric measures obtained subsequently, and (2) accuracy of recommendations for patient management made on the basis of Ecog results. The latter was determined by parental experience, educational placement and achievement, and information from medical and paramedical personnel currently managing the children. These data indicate that Ecog test results are valuable in helping select between possible management alternatives in children who are not testable by behavioral means.

Tone burst electrocochleography in humans.

Using tone burst stimuli with fixed parameters of rise time and duration, a functional relationship has been demonstrated between frequency and intensity of the stimulus and peak latency of electrocochleographic recordings. The feasibility of a "map" of the human cochlear partition has been shown for frequencies above 2 kHz.

Quinine-induced alterations in drug disposition.

In normal volunteers, chronic quinine administration shortened plasma antipyrine half-life and significantly increased the intraindividual correlation between the disposition of quinine and antipyrine. Decreased plasma antipyrine half-life appears to be due to a quinine-induced enhancement of antipyrine metabolism. A dose-dependent prolongation of plasma quinine half-life was observed and attributed primarily to an increased apparent volume of distribution of quinine, although our data did not permit separation of an effect on quinine metabolism from an effect on quinine distribution between the peripheral and central compartments.

Fluorometric assay of bethanidine in plasma.

A fluorometric method for determining bethanidine in blood plasma is described. The bethanidine is extracted into chloroform, a drug-dye complex with eosin Y is formed, and the fluorescence is measured (excitation, 535 nm; fluorescence, 560 nm). The assay detects 0.