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At least 73 records · Page 4Linked to original sources
PubMed1983

Clinical implications of experiments on alteration of the labyrinthine fluid pressures.

Hearing is affected by changes in hydrostatic pressure of the perilymph, but very high pressures are required to produce a significant loss. Among the observed findings in cats are a rapidly reversible decrease in the sensitivity of the cochlear microphonic that is greater for low frequencies, harmonic distortion and reduction of dynamic range as measured by the input-output function for the cochlear microphonic, and a change in the summating potential from negative to positive. These changes are attributed to a temporary reduction in the size of the cochlear duct due to a shift of water molecules out of the cochlear duct into the blood until the resulting increase in osmotic pressure balances the increase in hydrostatic pressure. Consequently, the organ of Corti is biased "upward" away from the scala tympani. Increasing the hydrostatic pressure of the endolymph produces a "downward" biasing of the organ of Corti and has an opposite effect upon the summating potential. Presumably this is what happens in Meniere's disease. Because of the presence of the perilymphatic canaliculi, the locus of the hydrostatic pressure effect is assumed to be in the region of the reticular lamina. A theory has been developed to explain why cochlear function is very sensitive to relative differences between the hydrostatic pressures of the perilymph and the endolymph but is resistant to large variations in the absolute magnitudes of those pressures. Some of the clinical implications of this theory are discussed.

Animals↗
PubMed1998

Importance of type IV collagen, laminin, and heparan sulfate proteoglycan in the regulation of labyrinthine fluid in the rat cochlear duct.

The distribution of major components of the basement membrane, such as type IV collagen, laminin, and heparan sulfate proteoglycan (HSPG), was investigated in the rat cochlear duct. Immunofluorescence demonstrated that type IV collagen, laminin and HSPG were distributed along capillaries in the cochlear duct, including the stria vascularis, spiral ligament, spiral prominence and spiral limbus. Additionally, type IV collagen, laminin and HSPG were found to be distributed from the basement membrane of Reissner's membrane to that of the spiral prominence in a linear pattern. The scala media was surrounded by these basement membrane components, demarcating endolymph from perilymph, along epithelial cells except at the stria vascularis. These findings suggest that type IV collagen, laminin and HSPG create the anatomical separation between endolymph and perilymph, thus indicating that they may be involved in the regulation of fluid transport between the endolymph and perilymph.

Animals↗
PubMed1999

[Preoperative evaluation of translabyrinthine cholesteatomas by MRI].

PURPOSE: Hearing preservation is one of the major goals of surgical resection of invasive cholesteatomas. Patients were prospectively evaluated using a 3D-CISS MR acquisition in order to improve the detection of perilymphatic fistulae. MATERIALS AND METHODS: 16 patients (10 M, 6 F) presenting with a primary (1 case) or a secondary (post-otitis) middle ear cholesteatoma extending to the osseous labyrinth (as defined by HR-CT) were evaluated at MR (1.5 T Vision, Siemens). The 3D-CISS sequence (TR: 12.25 ms, TE: 5.90 ms, flip angle: 70 degrees, slice thickness: 1 mm, matrix: 307 x 512, FOV: 200) allowed detection of invasion of the membranous labyrinth using a 3 level grading scale: 1) normal fluids, 2) focal and 3) diffuse obliteration of labyrinthine fluid. RESULTS: While CT showed a definite osseous labyrinthine fistula, the 3D-CISS sequence depicted either a normal membranous labyrinth (9 cases), a focal obliteration of the basal turn (1 case) or lateral semi-circular canal (3 cases) or a diffuse obliteration of the labyrinthine fluid (3 cases). Diffuse obliteration of the labyrinth fluid and 1 out 3 cases of focal obliteration of the semi-circular canal were found to have perilymphatic fistulae at surgery. None of the normal labyrinths were associated with perilymphatic fistula formation. CONCLUSION: The 3D-CISS sequence allows a comprehensive preoperative evaluation of the membranous labyrinth. Loss of signal from the labyrinthine fluid due to invasion or compression of the membranous structures accounts for the lack of specificity of the technique.

Adult↗
PubMedDate not supplied

Constructive interference in steady state-3DFT MR imaging of the inner ear and cerebellopontine angle.

PURPOSE: To assess the value of a three-dimensional Fourier transformation MR technique "CISS" (constructive interference in steady state) in imaging the inner ear. SUBJECTS: We studied 50 normal inner ears (40 axial, 10 coronal) and 10 pathologic inner ears in 60 patients. RESULTS: The cochlea, semicircular canals, and vestibulum were visualized in detail. Cranial nerve VII and the cochlear, superior vestibular, and inferior vestibular branch of cranial nerve VIII were identified in 90%, 94%, 80%, and 88% of the cases, respectively. A vascular loop was recognized inside the internal auditory canal in 6%, and in the porus in 30%, of the cases. The high signal of the cerebrospinal fluid and labyrinthine fluids (perilymph and endolymph) on the CISS images made excellent delineation of tumors in the cerebellopontine angle and internal canal possible and allowed detection of tumoral labyrinth involvement. The thin sections, high resolution of the images, and capability of producing multiplanar and three-dimensional reconstructions often offered additional information. CONCLUSIONS: The CISS sequence allows detailed study of the normal and pathologic inner ear and promises to be highly valuable in the demonstration of the vascular loop.

Adolescent↗
PubMed2002

Intratympanic ciprofloxacin and the human labyrinthine sampling model.

OBJECTIVE: The aim of the study was to investigate the potential absorption of intratympanic ciprofloxacin through the human round window membrane. STUDY DESIGN: A prospective study. METHODS: Ciprofloxacin was instilled into the middle ear of 10 patients undergoing acoustic tumor removal. The lateral semicircular canal and vestibule were subsequently opened and, using a microsyringe, labyrinthine fluid was aspirated. A sample each of serum and cerebrospinal fluid was also drawn. RESULTS: Into each middle ear, 0.5 mL ciprofloxacin (0.3%) was instilled. The time interval between the ciprofloxacin application to the round window membrane and sampling of labyrinthine fluid and plasma ranged from 9 to 120 minutes. There was no measurable ciprofloxacin in the labyrinthine fluid, cerebrospinal fluid, or serum of 10 patients. CONCLUSION: The lack of measurable absorption of intratympanic ciprofloxacin into the inner ear indicates that the chance of ototoxicity when ciprofloxacin is used clinically, even in the presence of a tympanic membrane perforation, is low.

Aged↗
PubMed2002

Rapid elevation of gentamicin levels in the human labyrinth following intravenous administration.

HYPOTHESIS: Adequate quantities of labyrinthine fluid can be sampled from the human labyrinth to perform quantitative analysis of medications. A rapid elevation of intralabyrinthine gentamicin levels after intravenous administration can be measured. A model for the sampling of human inner ear fluid in this manner is described. BACKGROUND: The risk of aminoglycoside ototoxicity has been a long-standing concern. The kinetics of gentamicin diffusion into the inner ear have been extrapolated to humans from various animal models. The validity of extrapolation to humans is unknown. We have developed a new model to measure the uptake of gentamicin in vivo. METHODS: A single intravenous dose of gentamicin (80 mg) was given perioperatively to 13 patients undergoing translabyrinthine acoustic neuroma surgery. The lateral semicircular canal and vestibule were opened and a microsyringe was used to obtain a sample of labyrinthine fluid concomitant with a serum sample. The gentamicin concentration of the labyrinthine fluid and serum was analyzed using a standard chemistry analyzer. RESULTS: After parenteral administration of gentamicin, fluid was obtained from the inner ear of 13 acoustic neuroma patients. Inner ear concentrations were between 1.0 and 3.8 mg/L. Serum gentamicin levels ranged from 1.2 to 10.5 mg/L. CONCLUSIONS: This method allows the sampling of intralabyrinthine fluid in humans. Gentamicin was noted immediately in the labyrinth after intravenous administration. This model may be expanded to measure other compounds given either by intravenous or transtympanic routes.

Adult↗