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PubMed1988

[Perilymphatic fistula. Diagnostic and therapeutic difficulties].

The symptoms and signs of perilymphatic fistulae (PLF) are very varied and frequently misleading. The operative demonstration of a perilymph leak is not always obvious and the therapeutic results are sometimes disappointing. The study of 26 cases demonstrates certain concepts concerning the diagnostic and therapeutic difficulties. Any atypical cochleovestibular symptoms, particularly occurring in a traumatic context, should suggest the possibility of PLF. Exploratory surgery must be performed according to a rigorous protocol in order to demonstrate the fistula. Search for a fenestra ovalis sign due to pressure on the membrane of the fenestra rotunda may help to reveal a lesion of the annular ligament. Simple filling of the breach is not always effective, especially at the level of the stapes. Stapedectomy frequently constitutes the best solution for fistulae of the fenestra ovalis.

Adult↗
PubMed1988

[Oxygen partial pressure measurements in the perilymph and scala tympani in normo- and hyperbaric conditions. An animal experiment study].

The purpose of this study was to examine the influence of hyperbaric oxygen on the oxygen tension (pO2) in the normal inner ear. We examined 16 anaesthetised guinea pigs by means of an oxygen-sensitive micro-coaxial needle electrode, using the method described by Baumgaertl and Luebbers. In all animals the pO2 in the perilymph of the scala tympani fell by 34% of the original value during insertion of the sensor into the scala tympani. After we had flooded the hyperbaric chamber with pure oxygen under normobaric conditions the pO2 increased by 244.3% of the original values. Furthermore the pO2 increased by 9.4 times the original values during hyperbaric oxygen at 1.6 bar.

Animals↗
PubMed1988

[Simultaneous determinations of oxygen partial pressure in the scala tympani, electrocochleography and blood pressure measurements in noise stress in guinea pigs].

In 14 guinea pigs the pO2 in the perilymph of the scala tympani fell to 50%-80% of the original value during exposure to noise consisting of 4,000 Hz clicks with a repetition rate of 20/s, 100 dB CHL = 120 dB SPL p.e., repeated twice over a period of 24 minutes each time. For the measurements of the pO2 we used the thin 0.5 micron micro-coaxial needle electrode described by Baumgärtl and Luebbers, which was placed through the round-window membrane in the scala tympani to a depth of 600 micron. The simultaneously recorded CAP latency times were prolonged by 0.8 ms at a test loudness of 60 and 80 dB CHL. The amplitudes of the CM had declined by 60%-70% of the original values at a test loudness of 80 dB SPL p.e. The intra-arterial blood pressure in the common carotid artery of all animals remained constant. As the cortilymph spaces communicate with the perilymph of the scala tympani, our measured decline of pO2 in the perilymph could indicate a cortilymph hypoxia. During exposure to noise the oxygen-dependent Na+ and K+ pumps, which maintain the ion balance and function of the organ of Corti, can decompensate due to lack of oxygen. That would lead to a K+ contamination of the cortilymph and to an intracellular Na+ accumulation, which can cause microstructural damage (hair cell-cilia fusion, hair cell, synaptic and dendritic swelling, hair cell contraction and sustained depolarization), which would be reflected in the CMs and CAPs.

Animals↗
PubMed1988

[Topography of the round window and its significance for the surgical therapy of perilymph fistulas].

The clinical findings concerning the diagnosis of a rupture of the round window membrane vary widely. Therefore, microtopography of the round window was studied using 45 serially sectioned human temporal bones of the Wittmaack Collection, ENT Clinic, University of Hamburg. Our morphometrical data show a great variety in respect of the dimension of the round window membrane and the angle between the window membrane and the tympanic membrane. The extension and the microtopography of the promontory are as variable as the mucosal folds in the round window niche. It can be concluded that a direct view of the round window membrane is possible only in rare cases. Surgical manipulations to improve the view of the round window should be avoided because of the danger of an iatrogenic lesion of the inner ear.

Adolescent↗
PubMed1987

Perilymph fistula resulting from microfissures.

Perilymphatic fistulas are well documented in the otolaryngologic literature as a cause for both auditory and vestibular symptoms. The anatomic location of fistulas has been clinically confirmed in both the oval and round windows. Furthermore, membranous tears within the cochlea have been described post mortem and may be the cause of the remaining fistulas which are suspected but not confirmed surgically. A fourth source of perilymph fistula has previously been suggested by Okano and Harada. During the past several years, surgical confirmation of perilymph leakage from two microfissure areas has been observed. These cases will be briefly discussed along with their clinical implications. Speculation as to the type of hearing loss caused by fistulas will be offered. Hypotheses concerning the various symptoms encountered in patients and the location of the defect will also be addressed.

Adult↗
PubMed1987

[Scanning electron microscopy studies of the structure of tissue in the cochlear opening of the cochlear aqueduct].

The structure of the internal and external tissue of the cochlear opening of the cochlear aquaeduct was examined by light microscopy on semithin sections and by scanning electron microscopy. The whole area is filled with a net of mesenchymal cells. The cell axes are randomly orientated inside the aquaeduct. On the outside of the cochlear aquaeduct fibrocytic tissue fills a space which is triangular in cross-section between the basal part of the cochlea wall of the tympanic scala and the middle portion of the round window membrane. In this area the direction of the net is uniform and it gives the impression of anchorage of the round window membrane on the perilymphatic side. The rim bordering the perilymphatic space is a dense net but not fully closed. The scanning electron microscopic pictures taken perpendicular to this border structure show clearly a texture of mesenchymal cells with open spaces. No closed "membrana limitans" was found. The possible function of the fixation of the round window membrane to the perilymphatic space giving rise to an asymmetric perilymph movement is discussed with regard to the physiology of sound transmission.

Animals↗
PubMed1987

Effects of isosorbide on perilymphatic pressure and oxygenation.

Using a servocontrolled micropipet pressure measuring system, the effect of intravenous and oral administration of isosorbide, a hyperosmolar agent that is an anhydrate of sorbitol, was examined in 11 fasting cats. Following intravenous administration of 2 g/kg of the agent, perilymphatic pressure has shown, on the average, a significant reduction of 136% of the initial value (3.6 +/- 0.3 mm Hg). A strong rebound phenomenon, however, with a 61% rise to the initial value, was noted, and this did not come down in 3 hours. On the contrary, no rebound phenomenon was noted after oral administration, which caused a significant 60% drop in perilymphatic pressure for more than 90 minutes. Using polarographic technique, perilymphatic oxygen tension was measured and showed a maximal increase of 145% to the initial value. The time it took to reach the maximal PO2 tension was equal to the time it took to come down to the minimal perilymphatic pressure. This is a strong indication that isosorbide improves perfusion and increases blood flow of the inner ear vessels.

Administration, Oral↗
PubMed1986

[Pharmacokinetics of amikacin in the perilymph and blood serum. An approach to the comparative evaluation of the potential ototoxicity of aminoglycoside antibiotics].

The pharmacokinetics of amikacin in serum and perilymph was studied on guinea pigs treated with its single subcutaneous administrations in doses of 100, 200, 400 and 800 mg/kg. Proportional relation between the values of the areas under the concentration against time curves of the antibiotic in serum and perilymph was shown. It suggested that the level of the antibiotic penetration into the internal ear might be predicted by the area under the concentration against time curve of the aminoglycoside. It was demonstrated that in equitherapeutic doses when D/Deq = 1 aminoglycosides had different areas under the concentration against time curve. Thus, the area under the curve of amikacin was 2.2 times higher than that of sisomicin. It was also demonstrated that the angle coefficient characterizing the relationship between the area under the concentration against time curve in perilymph and the dose standardized with respect to the equitherapeutic value was markedly higher for amikacin than for sisomicin.

Amikacin↗
PubMedDate not supplied

The osmotic effect of glycerol on the stria vascularis and endolymph.

In the chinchilla, quantitative changes in strial thickness, area of the endolymphatic space, serum osmolality, and serum levels of glycerol, glucose, total protein sodium, potassium and chloride were determined at 1, 2, 3 and 5 h after the intraperitoneal administration of 6 g/kg glycerol. The serum osmolality, glycerol, glucose and potassium levels increased, while serum sodium and chloride decreased. Quantitative changes in cochlear structure included an increase in strial thickness and a decrease in area of the endolymphatic space. In all the animals (n = 50), the increase in strial thickness was closely correlated (correlation coefficient r = 0.57) to an increase in serum osmolality. This correlation with strial thickness improved (R = 0.71) when the interval between injection and animal sacrifice was used in combination with serum osmolality. The increase in stria thickness was also closely correlated to an increase in serum glycerol and to a decrease in serum chloride. A decrease in endolymphatic volume was found most consistently at 3 h after the i.p. administration of glycerol.

Animals↗
PubMed1987

Persistent traumatic perilymph fistulas.

Thirty-four ears have been explored to rule out perilymph fistulas resulting from ear trauma. Eight ears (24%) were identified with a fistula, often persisting months (average 7.5 months) after the precipitating injury. Repair of fistulas, even if done relatively late, markedly reduces vestibular symptoms and may improve low and middle frequency sensorineural hearing. Complications from negative explorations are rare.

Ear↗
PubMedDate not supplied

Perilymphatic calcium and VIII nerve action potentials during gentamicin bolus i.v. injections. A preliminary study.

Life-threatening human sepsis is often treated using bolus intravenous aminoglycoside injections with transient deafness as a reported side effect. Young adult cats were given various high dosages of gentamicin in bolus injections (1 ml in 30 s). Scala vestibuli calcium and gentamicin, blood gentamicin and compound action potentials of the VIII nerve were measured shortly after the injections and 45 min later. An obvious relationship could be demonstrated between levels of gentamicin, decreased calcium content and acoustic thresholds elevation. Even after a high dose of 175 mg/kg that abolished action potentials at t = 2 min, recovery invariably occurred. It is believed that the reported transient hearing loss in humans may be partly attributable to a temporary blockage of calcium by gentamicin.

Action Potentials↗