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At least 127 records · Page 7Linked to original sources
PubMed1990

Cochlear and cerebrospinal fluid pressure: their inter-relationship and control mechanisms.

The patency of the cochlear aqueduct is a key factor in intra-cochlear hydromechanics. If patent, the cerebrospinal fluid (CSF) provides the reference pressure for the perilymph and also to a large extent the endolymph, since Reissner's membrane can only withstand a relatively small pressure differential. The aqueduct often becomes sealed as a natural process of ageing. In this instance the reference pressure is from a source, its position unknown, within the boundaries of the cochlea itself. Relatively large and rapid changes in the cerebrospinal fluid pressure may result from everyday events such as coughing (ca. 175 mm saline) and sneezing (ca. 250 mm saline). The resistive nature of the cochlear aqueduct and the mechanical compliance of the cochlear windows are probably important factors in limiting the amount of stress, and therefore possible damage, which may occur to the cochlea and cochlear windows for a given pressure change within the CSF system. A narrow aqueduct and compliant cochlear windows reduce the risk of structural damage. In practice, this should mean that the risk of structural damage will be increased by any process which reduces the compliance of one or both of the cochlear windows, for example, extremes of middle ear pressure perhaps brought about by Eustachian tube dysfunction or rapid barometric pressure changes. Techniques are now available which provide non-invasive indirect measures of perilymphatic pressure and CSF-perilymphatic pressure transfer. The tympanic membrane displacement measurement technique has been used to provide reliable measures of perilymphatic pressure and CSF-perilymphatic pressure transfer on an individual subject basis.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMedDate not supplied

Effect of peroral glycerol administration on inner ear fluid electrolytes of guinea pigs.

After the oral administration of 50% glycerol (12 mL/kg), serum, CSF and inner ear fluids from scala tympani perilymph, scala vestibuli perilymph, and scala media endolymph were collected from normal guinea pigs under sodium pentobarbital anesthesia (25-35 mg/kg). The sodium and potassium concentrations were determined by microflame photometry. Increases in sodium concentrations were found in CSF, scala tympani perilymph, scala vestibuli perilymph, and cochlear endolymph. No significant change was observed in the serum. These sodium increases were considered to be due to the dehydration caused by the osmotic action of glycerol. Potassium concentration was increased only in scala tympani perilymph. Oral administration of glycerol was found to be more gradual and effective in dehydration compared to intravenous injection.

Administration, Oral↗
PubMed1977

Labyrinth and cerebral-spinal fluid pressure changes in guinea pigs and monkeys during simulated zero G.

This study was undertaken to explore the hypothesis that shifts of body fluids from the legs and torso toward the head contribute to the motion sickness experienced by astronauts and cosmonauts. The shifts in body fluids observed during zero-G exposure were simulated by elevating guinea pigs' and monkeys' torsos and hindquarters. Cerebral-spinal fluid pressure was recorded from a transducer located in a brain ventricle; labyrinth fluid pressure was recorded from a pipette cemented in a hole in a semicircular canal. An anticipated divergence in cerebral-spinal fluid pressure and labyrinth fluid pressure during torso elevation was not observed. The results of this study do not support a fluid shift mechanism of zero-G-induced motion sickness. However, a more complete test of the fluid shift mechanism would be obtained if endolymph and perilymph pressure changes were determined separately; we have been unable to perform this test to date.

Animals↗
PubMed1977

[Determination of the perilymph density in the cochlea of guinea pigs (author's transl)].

The perilymph density of the sc. tympani, sc. vestibuli and the density of liquor cerebrospinalis in guinea-pigs are measured by determination from mass and volume of the fluid column in a glass capillary tube. For the density of perilymph in sc. vest. a value of (formula: see text) in sc. tymp. a value of (formula: see text), and for liquor a value of (formula: see text) was obtained.

Animals↗
PubMed1986

Possible implication of an efferent neuropathy in vestibular upset.

This essay examines two possible mechanisms whereby a neuropathy affecting the efferent vestibular innervation may cause incoordination of vestibular afferent input to the Vestibular Integrating Centres: firstly, by loss of the normal fine control of afferent impulses; secondly, by a disruption of the sodium-potassium pump mechanism that maintains the ionic stability of the inner ear fluids.

Humans↗
PubMed1987

Na and nonelectrolyte entry into inner ear fluids of the rat.

Kinetics of hydrophilic solute entry into endolymph (EL), perilymph (PL), and cerebrospinal fluid (CSF) were studied after intravenous administration (sodium, urea, glycerol, mannitol, sucrose) and cerebral lateral ventricle injection (urea, sucrose) of tracers in anesthetized rats. Samples of cochlear EL, PL of scala vestibuli (PLV), PL of scala tympani (PLT), and cisternal CSF were obtained. The data showed slow entry of tracers in PLV, PLT, and CSF as follows: Na greater than urea greater than mannitol approximately sucrose; slower entry of mannitol and sucrose in PLT and CSF than in PLV; 1 h delayed peak of radioactivity in PLV compared with the immediate peaks in PLT and CSF after CSF injection, and the value of PLV peak was 13% that in CSF; extremely slow entry of nonelectrolytes in EL. These results indicate that PLV originates mainly from plasma across a blood-perilymph barrier that restricts the entry of small hydrophilic solutes. The blood-perilymph barrier is most likely composed of an endothelial barrier associated with an epithelial secretion. The latter could be located at the vasculo-epithelial zone of the spiral limbus.

Animals↗
PubMed1976

Quantitative assessment of perilymph sources.

The problem of the perilymph origin--influx of cerebrospinal fluid (CSF) versus ultrafiltration within the cochlea--cannot be solved by mere qualitative proofs of tracer passage through the cochlear aqueduct. In order to gain quantitative data on the possible perilymph sources, an experimental study was designed to follow the time course of dye concentrations in the cisternal CSF and in the perilymph after tracer injection into the CSF at the vertex. By comparing the resulting concentration peaks in both fluids, the mean peak of the perilymph tracer concentrations was found to reach 36% of the maximum CSF concentration only. It is concluded that the local perilymph production within the cochlea exceeds the influx of CSF by a ratio of about 2:1. A working hypothesis of the double perilymph origin is discussed.

Animals↗
PubMedDate not supplied

[Protein study on perilymph susbstitution during cerebrospinal fluid flow through cochlear aqueduct].

Total protein contents in the perilymphy of Scala vestibuli and Scala tympani as well as in the cerobrospinal fluid (CSF) of guinea-pigs were determined, by which specimens were taken under the following various conditions: With or without subarachnoidal puncture before perilymph collection, by varying the amount of perilymph taken from Scala tympani, by fractionating collection and under post mortem condition. The results suggest that under physiological conditions the CSF also flows through the cochleae aqueduct and the protein concentration in the Scala tympani decreases especially in the basal winding. Because the protein content in CSF is inaverage four times lower than in fluids of the inner ear it is of preference to consider the question of connection between the CSF and the fluids of the inner ear. In the specimens taken the blood contamination was estimated on the basisof erythrocytes in the connection capillaries under microscope. The protein content in the perilymph of Scala vestibuli was found significantly higher in relation to perilymph of Scala tympani.

Animals↗