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[Gherini-Causse endo otoprobe and HGM argon laser. Value in the surgery of ear abnormalities].

Performing a stapedectomy in a slightly fixed otosclerotic footplate may induce an excessive motion of the labyrinthine fluids, damaging inner ear membranes and Corti hair cells fragilized by proteolytic enzymes. The fluid motion in the cochlear canal is quantic size only. The replacement of a slightly fixed footplate by an ideal compliance and impedance transmitting device, may allow the surgeon to get a tremendous improvement of hearing (as a Meniere disease). The Gherini-Causse multi-use endo-otoprobe combined with a HGM Argon Laser, if associated with a Skeeter Oto-tool drill, looks to be an efficient and safe solution to this otologic surgical challenge.

Argon

[Effects of body posture on cochlear performance].

Experimental research has demonstrated that changes in body position influence auditory function and, specifically, supine position produces a sensorineural hearing loss at low frequencies. The hypotheses to interpret these phenomena are principally referred to an increase of hydrostatic pressure of labyrinthine fluids. In order to evaluate the effects of head position on the cochlear performance a modern test battery has been performed to study cochlear function in 11 normal subjects ranged in age from 22 to 34 years. The tests (Remote Masking:RM; Brief Tone Audiometry:BTA; Critical Ratio:RC) have been evaluated in two positions: sitting upright and supine with the head at a 20 backward angle. The results of our research have shown that in all the cases, the supine position produces a significant shift of the auditory threshold at 250 and 500 Hz, and a decrease of RM values in about all of the cases. We have estimated non statistically significant differences for the RC and BTA values, in more than half of the ears tested. On the basis of the significance given to RM, BTA, RC: we can deduce that the modifications of the auditory performance related to an increase in perilymphatic hydrostatic pressure, induced by the head position are produced by an increase in rigidity of the mechanical vibratory structures of the cochlea rather than the expression of sensorineural damage.

Adult

[Clinical aspects of sudden deafness and vestibulopathy].

Clinical aspects of sudden deafness and sudden vestibular loss. The cases of sudden deafness and/or sudden vestibular loss are 90% idiopathic. Initially they can be overlooked but they can be responsible for an important sensorial impairment. In 65% of cases, and within the first two weeks, there may be a relevant or complete recovery or functional compensation. Etiology and pathogenesis are considered to be pluri-factorial; multiple virus infection including the Herpesvirus family, is the most relevant and better documented cause. Such an infection is responsible for a derangement of inner ear microcirculation, ions imbalance at labyrinthine fluids level, reduction of receptors and nervous supply function. Therapy is essentially symptomatic and therefore the most widely used drugs are cortisonics and heparin. In the Author's opinion also dextran 40, by slow endovenous drip, and carbogen (O2 95% + CO2 5%), by inhalations, are very effective with only rare contraindications. The occurrence of an important number of spontaneous improvements or even recoveries does not authorize therapeutic abstension especially in severe or delayed cases.

Hearing Loss, Sudden

Effect of urea on osmolality of perilymph.

Blood osmolality was altered in chinchillas by intravenous administration of urea. Serum osmolality peaked rapidly at 30 minutes after administration and decreased slightly to a plateau for 180 minutes. Perilymph and CSF osmolality lagged substantially behind the increase in serum osmolality and equaled serum osmolality only after one hour. Perilymph osmolality followed changes in the serum up to 60 minutes with a definite time lag. This phenomenon suggests the existence of a selective blood-labyrinth barrier that is permeable to urea and water. However, the time lag due to the barrier may permit the reduction of hydrostatic pressure in the labyrinth. The results of the present study seem to render partial explanation of improved hearing in patients with Meniere's disease who were treated with urea.

Animals

Effects of posture and age on tympanic membrane displacement measurements.

This study used changes in posture to investigate the transmission of cerebro-spinal fluid (CSF) pressure changes to the cochlear fluids in subjects falling into two age groups. Results were obtained from 32 subjects: 16 aged 19 to 32 years and 16 aged between 40 and 63. Measurements were made with the subject sitting upright and then at 63 degrees to the vertical, using a technique which measures displacement of the tympanic membrane in response to acoustic stimulation of the stapedial reflex. Changes in such measurements are believed to represent changes in perilymphatic fluid pressure. Statistical analysis of the results showed the magnitude of changes in Tympanic Membrane Displacement (TMD) measurements with postural change to be smaller in the older group than in the younger age group. In addition, a larger proportion of the older subjects showed no change in TMD measurements with change in posture. The proportion of subjects in each age group who showed no change in TMD measurements with change in posture was similar to the proportion of temporal bones of subjects of similar ages that had non-patent cochlear aqueducts as determined by a previous histopathological study. Audiometric testing revealed a link between hearing threshold and presumed patency of the communication routes between cochlear and cranial fluids. The magnitude of the tympanic membrane displacement was found to decrease with age in agreement with previous studies showing decrease of stapedial reflex magnitude with increasing age. It is suggested that the communication between cochlear and cranial fluids may be important in the pathogenesis of auditory dysfunction in several patient groups.

Adult

The dynamic posturographic pressure test for the presumptive diagnosis of perilymph fistulas.

A diagnosis of perilymph fistulas (PLFs) can be made only by identification of repeated accumulation of crystal-clear fluid from an otic capsule defect or labyrinthine window at tympanotomy. It would be highly desirable to base a decision to operate for the diagnosis and management of PLFs on a database that includes quantitative test data, which confirms, with a high probability, a clinical suspicion of PLF. This article reviews progress in the development of a test of the vestibular response to external auditory canal pressure changes as recorded by dynamic posturography. Based on results to date, it appears that a fistula test with dynamic posturography is more sensitive than those based on VOR responses. This may be due to the ability of dynamic posturography to isolate vestibular from both visual and somatosensory influences on motor responses during external canal pressure changes.

Ear Diseases

Osmolality changes in perilymph after systemic administration of glycerin.

Blood osmolality was altered in guinea pigs by intravenous administration of glycerin (glycerol). After glycerin administration, serum osmolality increased rapidly, reaching a plateau within 15 minutes. Perilymph osmolality lagged significantly behind the increase of serum osmolality and equalled serum osmolality only after one hour. While perilymph osmolality responded to changes of serum osmolality, there was some time lag noted in the response of perilymph, suggesting the existence of a blood-labyrinth barrier. It was observed that this barrier is permeably to glycerin and water, suggesting the possibility of transient reduction of hydrostatic pressure in the labyrinth by the injection of an osmotic agent into the systemic circulation.

Animals

[Otitis media and cochlea. Morphological and biochemical studies in guinea pigs (author's transl)].

The paper deals with: 1. the protein concentration in the perilymph (PL), the serum and the cerebrospinal fluid (CSF), 2. the protein pattern in the PL and 3. histological findings in the middle and inner ear in unilaterally ear-infected guinea pigs. The studies were performed 6 h to 21 days post infectionem (Fig. 1). The pathological changes in the middle ear, which, in most cases, were limited to the infected ear, were initially evaluated under the operating microscope and divided into 4 stages. The analytical and histological results were presented as functions of these stages. As the inflammation intensity increased, the protein concentration in the PL of the infected ears increased to a level exceeding that of the normal value more than ten times (Fig. 2). However, in the serum and in the CSF this concentration remained unchanged. Likewise, no significant protein increase in the PL of the contralateral ears was detectable in most cases. As the inflammation intensity increased, the number of the precipitation lines detectable immunoelectrophoretically increased in the PL of the infected ears (Fig. 3). An increase in the alpha1- and gamma-globulins and a decrease in Albumin was found by electrophoresis on cellulose acetate strips (Tab. 3). The histological findings correlated with initially established inflammatory stages of the middle ear mucous membrane (Tab. 4). As the inflammation intensity increased, the round window, too, was changed pathologically, so that in some cases of purulent otitis media middle ear secretion could enter the cochlea. The protein increase in the PL immediately after the infection is probably due to an increase in the blood vessel permeability in the inner ear.

Animals

Chemical composition in various compartments of inner ear fluid.

Sodium, potassium, chloride, glucose and total protein were determined in samples of scala vestibuli perilymph, scala tympani perilymph, CSF, cochlear endolymph and utricular endolymph from normal cats. Small but significant differences were evident in the concentrations of sodium and potassium between the scala vestibuli and scala tympani perilymph. It was also apparent that each compartment of endolymph has different values for sodium and potassium concentrations. Compared with the endolymph, the perilymph was found to contain a higher concentration of glucose and total protein. These findings are discussed from the view point of biological significance.

Cerebrospinal Fluid

Barrier systems in the inner ear.

Because of the highly complicated function of the central nervous system and sensory organs, barrier systems have necessarily developed to ensure stability of the extracellular fluids bathing these organs. Several barrier systems which can influence the composition of the inner ear fluids are discussed. They are the 1) blood-labyrinth barrier, 2) cerebrospinal fluid-labyrinth barrier, and 3) middle ear-labyrinth barrier. The experimental data are shown to indicate that these barriers serve to protect the inner ear through selective permeability. Arachidonic acid metabolites, particularly compounds of the prostaglandin series, were identified in perilymph, and were increased by the administration of stress-related hormones, and decreased after aspirin injection. The inner ear fluid composition responds to the changes of the surrounding fluid containing compartments. However, the degree of response appears to depend on the level of changes induced in the surrounding compartments. The concept of a threshold concentration of toxic substances in middle ear effusion to induce inner ear damage is also proposed.

Body Fluid Compartments

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

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

[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

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

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