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PubMed1984

Probenecid reduces cochlear effects and perilymph penetration of furosemide in chinchilla.

Previous investigation has suggested that the ototoxicity of furosemide is related to penetration of the drug into the inner ear and that active drug transport out of the inner ear may be responsible for maintaining the serum-perilymph drug concentration gradient. We further tested this hypothesis by investigating the endocochlear potential (ototoxicity) and furosemide perilymph concentrations after furosemide administration to chinchillas pretreated with the organic anion transport inhibitor, probenecid. Probenecid pretreatment attenuated the fall in endocochlear potential seen after furosemide (25 mg/kg i.v.): untreated, 58.6 +/- 27.0 mV; probenecid pretreatment, 14.1 +/- 11.9 mV (P less than .01). Furosemide concentrations in perilymph were correspondingly lower after probenecid (P less than .003), although serum furosemide concentrations were not affected by probenecid pretreatment. Diuresis, measured over an 8-hr period after furosemide, was also uneffected by probenecid. These results confirm the proposed relationship between inner ear furosemide concentrations and the occurrence of ototoxicity due to this drug. However, the determinants of penetration of this drug into the inner ear are unclear. The observation that probenecid pretreatment attenuates the ototoxic effect of furosemide while the diuretic effect is preserved suggests this drug combination warrants further investigation.

Animals↗
PubMed1984

Perilymphatic fistula--a definitive and curable cause of vertigo following head trauma.

Vertigo or disequilibrium occurring in patients after concussive and nonconcussive head trauma may be due to a pathologic perilymphatic fistula from the inner ear through the oval and round window areas of the middle ear. Of 33 patients who had successful grafting of the fistulous area at middle ear exploration, 32 had resolution of vertigo, and 12 of 23 who had an associated hearing loss had improved hearing. Perilymphatic fistulas associated with vertigo and hearing loss after head trauma can be diagnosed with great certainty and are surgically curable in the great majority of cases. Patients with post-concussive syndrome, whose symptoms include vertigo or disequilibrium, should have a thorough otologic evaluation for the possibility of a perilymphatic fistula.

Craniocerebral Trauma↗
PubMed1984

Auditory evoked potentials--the cochlear summating potential in detection of endolymphatic hydrops.

With an expanded clinical and normative SP amplitude series, we have re-examined the incidence of SP enlargement in clinically defined Meniere and cochlear ears. The overall incidence of SP enlargement in the expanded series is somewhat less than that found in our previous study (56% versus 68%). This difference may be due to considerable preselection of patients included in the previous smaller clinical population, since many of these patients were recruited for the study because of diagnosed Meniere's disease. In contrast, the present, larger clinical population was selected from our normal service referral base, and thus contains a much higher percentage of diagnostic problems. The comparison between SP enlargement and hearing levels demonstrates that the SP test for Meniere's disease must be interpreted in the light of high-frequency hearing levels. If the patient has normal or near-normal hearing (4- to 8-kHz hearing levels 25 dB or less), SP enlargement will not be a good criterion for detecting the presence of Meniere's disease. Gibson and colleagues and Kumagami and associates have reported similar observations. Also, in the presence of severe high-frequency hearing loss (above about 70 dB), SP enlargement occurs relatively infrequently among ears with clinical diagnoses of Meniere's disease. However, in the mid-range (25 to 70 dB) of high-frequency loss, SP enlargement appears to provide a reasonably accurate test for Meniere's disease (with a "hit rate" among clinically defined Meniere ears of about 71%).(ABSTRACT TRUNCATED AT 250 WORDS)

Brain Stem↗
PubMed1981

Experimental study on the perilymphatic pressure.

The hydrostatic pressure was successfully and accurately measured through the round window membrane of the cat over a wide pressure range and long duration using glass micropipets of 1-5 micrometer tip inner diameter and an active nulling pressure measuring system. The dynamic changes in perilymphatic pressure occurring after inhalation of different gas mixtures (5 percent CO2 and 95 percent O2/carbogen, 5 percent and 10 percent CO2 in room air) were recorded. The maximal oxygenation of the perilymph combined with minimal increase in pressure was achieved following inhalation of carbogen. The correlation between variations of pressure of the perilymph and of the systemic blood circulation shows that a regulatory system is present in the inner ear vessels. The pressure measuring system used has proven to have all the requirements that are needed for its use in humans.

Animals↗
PubMed1983

[Effect of changes in electrolyte composition of the perilymph on endocochlear potentials].

Perfusion of the cochlear perilymphatic space was performed in guinea pigs with complete or partial removal of K+, Na+ or Ca++ from the solution. The most obvious changes of the endocochlear potential occurred in the deficiency of Na+ in the perilymph: i. e., after a short increase the potential steadily diminished in accordance with the degree of Na+ deficit in the perilymph. The deficit of K+ in the perilymph caused a lesser and reversible reduction of the potential. The absence of Ca++ in the perilymph did not affect the potential.

Animals↗
PubMed1981

Perilymph total protein levels associated with cerebellopontine angle lesions.

The total protein levels in the perilymph of patients with acoustic neuromas, meningiomas, and Meniere's disease are contrasted. All specimens were obtained from the lateral semicircular canal during removal of the bony labyrinth. Any specimens with significant contamination by hemoglobin or serum proteins, as judged by the presence of hemoglobin/haptoglobin complexes, were discarded from this study. The findings of greatly increased perilymph protein levels in the tumor groups confirmed the reports of other workers. The levels in the Meniere's disease group compared favorably with the normal protein levels in perilymph. A very significant (p Less Than 0.05) difference between the acoustic neuroma group and the meningioma group is noted. This difference is probably tumor related, because in all cases of both groups, tumor entered and filled the internal auditory meatus.

Cerebellopontine Angle↗