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PubMedDate not supplied

Monitoring of the glycerol test with sinusoidal harmonic acceleration in Menière's disease patients.

Changes in auditory pure tone threshold and speech discrimination and the phase and gain in the sinusoidal harmonic acceleration test were measured in subjects with endolymphatic hydrops (Meniere's disease) following the administration of glycerol. Although all subjects showed a marked improvement in auditory function, a comparable change in vestibular function, as measured by the sinusoidal harmonic acceleration test, was not observed.

Acceleration↗
PubMedDate not supplied

Perilymph fistula: the Stanford experience.

Seventy-eight tympanotomies were performed to determine the presence of perilymph fistulas (PLFs); of these, 51% were found. The oval and round windows of all patients were grafted, whether PLFs were present or not. Of those patients with PLFs, 64% had resolution of their major symptom; when no PLF was found, 44% had a similar outcome. We concluded that 1) PLFs often behave as if they are epiphenomena in relation to hearing and balance, 2) PLFs can be intermittent, 3) PLF surgery is disappointing for restoration of hearing in sudden hearing loss when compared to the rate of spontaneous recovery, 4) stabilizing a fluctuating or progressive loss is a more realistic goal, and 5) establishing preoperative criteria for exploration is still a problem.

Adolescent↗
PubMed1989

Lack of effect of carbonic anhydrase inhibition on direct measurements of endolymph bicarbonate.

In the past, sodium, potassium, and chloride have been measured in endolymph directly, but bicarbonate has been measured only indirectly. We sampled endolymph directly while monitoring endocochlear potentials in normal and methazolamide-treated guinea pigs. Bicarbonate was determined in samples by use of a method that depends on reduction of NADH to NAD linked to malate formation from oxaloacetate. In 11 normal animals, the bicarbonate in endolymph was 20.2 mM +/- 4,4 mM (mean +/- standard deviation); in six of these, plasma bicarbonate was 23.1 mM +/- 3.5 mM. Nine animals treated with methazolamide (carbonic anhydrase inhibitor) had an endolymph bicarbonate of 19.5 mM +/- 3.9 mM; plasma bicarbonate in five of these was 25 mM +/- 3.2 mM. Carbonic anhydrase inhibition did not significantly affect endolymphatic bicarbonate levels.

Animals↗
PubMed1989

Round window membrane and perilymph in experimental otitis media with effusion.

To investigate the influence of middle ear effusion (MEE) on perilymph (PL), an experimental otitis media with effusion (OME) was manufactured in chinchillas by injecting the tympanic cavity with immune complexes. The presence of MEE lasted for up to 9 days after the injection of immune complexes. Perilymph was aspirated on the fourth, tenth, and 21st days after the inoculation. The mean concentrations of albumin, immunoglobulin G, histamine, and prostaglandin E2 (PGE2) were significantly greater in PL from ears with induced OME than in that from normal control ears. The 3H-PGE2 placed on the round window membrane of pathologically affected ears passed into PL in significantly greater amounts than in normal control ears. The findings indicate that the immune complexes placed in the middle ear cavity affect the biochemical milieu of PL, and that MEE is a result of immune complexes.

Albumins↗
PubMed1990

Histopathologic study of the perilymph-suctioned labyrinth.

A small amount of perilymph was suctioned from the scala tympani through the round window membrane of guinea pigs. The animals either were killed immediately after the suctioning or were kept alive for 1 to 3 months. For morphologic study, the conventional celloidin embedding method was employed, and the temporal bones were serially sectioned. Various kinds and degrees of changes in the membranous labyrinth were observed: hydrops, collapse, and rupture. Loss of outer hair cells in the upper turns of the cochlea was noted in the 1- to 3-month recovery specimens. These findings are identical to those found in animals in which artificial perilymph was injected into the subarachnoid space in order to produce experimental perilymphatic fistula. After comparing morphologic changes of the membranous labyrinth following use of each method, we concluded that perilymph suctioning from the round window can be used as an animal model of perilymphatic fistula.

Animals↗
PubMed1990

Experimental endolymphatic hydrops: are cochlear and vestibular symptoms caused by increased endolymphatic pressure?

The correlation between inner ear pressure and cochlear function was investigated in guinea pigs with unilaterally obliterated endolymphatic sacs and ducts. In 11 animals that developed endolymphatic hydrops, auditory thresholds as monitored by auditory evoked action potentials had increased with recruitment. Most of these animals also experienced episodes of spontaneous nystagmus. In control ears endolymphatic pressure did not differ more than 0.5 cm H2O from perilymphatic pressure. In six of 11 hydropic ears, endolymphatic pressure was more than 0.5 cm H2O higher than perilympathic pressure; auditory thresholds in all these ears had deteriorated within 2 weeks before pressure recording. No further hearing deterioration within this period was noted in five hydropic ears with endolymphatic pressure equal to or lower than perilymphatic pressure. Endolympathic-perilymphatic pressure gradients may contribute to auditory threshold increase in endolymphatic hydrops, but are not its only cause.

Animals↗
PubMedDate not supplied

Perilymphatic communication routes in the auditory and vestibular system.

Horseradish peroxidase was injected into the foramen magnum and oval window of guinea pigs to determine perilymphatic communication routes and boundaries. The primary route to the auditory system appeared to be through the cochlear aqueduct. Perineural spaces of the eighth nerve contributed to this communication and provided the principal perilymphatic communication routes to the vestibular system. Light and electron microscopic examination were used to identify membrane permeability and define boundaries in the epithelial lining of the auditory and vestibular endorgans.

Animals↗
PubMed1983

Management of sudden deafness.

Measurements according to the polarographic principle in cats have shown that the factors influencing the perilymphatic oxygen tension are the arterial PCO2, the arterial PO2, and the systemic blood pressure. In patients with sudden deafness, the oxygen supply to the vestibular tissues is significantly reduced but the response to carbogen is still possible. The vasodilation induced by carbogen in sudden deafness is not accompanied by a reduction (stealing effect) but by an increase of perilymphatic oxygenation. Therefore carbogen inhalation was used for the treatment of sudden deafness. In a prospective randomized study, carbogen inhalation yielded significantly better results than the intravenous infusion of papaverine and low-molecular dextran. Carbogen inhalation is recommended for the effective, noninvasive treatment of sudden deafness.

Animals↗
PubMed1983

Membranous ruptures in Meniere's disease: existence, location, and incidence.

Whether or not attacks of Meniere's disease are related to ruptures in the membranous labyrinth is still a point of contention. To help clarify this point, we used light microscopy to study the membranous labyrinth in 14 temporal bones with hydrops from patients with Meniere's disease, four bones with hydrops from patients without Meniere's disease, and 11 normal bones. Findings suggest that ruptures are specific to bones with hydrops from patients with Meniere's disease and that they occur more frequently in Reissner's membrane than in the vestibular membranes.

Ear, Inner↗
PubMed1983

Perilymph fistulas in infants and children.

During the years 1975 through 1981 we performed exploratory tympanotomies on 33 infants and children (44 ears) to verify the presumptive diagnosis of perilymph fistula (PLF). A PLF was identified at the round window, oval window, or both in 29 (66%) of the 44 ears explored. After surgery hearing was unchanged in 86%, improved in 5%, and worsened in 9% of the ears in which PLFs had been observed. Complaints of vertigo subsided in all children in whom a PLF was repaired. Preoperative factors determined to be highly suggestive of the presence of a PLF included the following: sudden onset of sensorineural hearing loss (SNHL), congenital deformities of the head, and abnormal findings on tomograms of the temporal bones, especially Mondini-like inner ear dysplasias. Middle ear abnormalities (primarily congenital) were observed in 20 of the 44 ears. Abnormal results of preoperative vestibular function studies, which included a fistula test, and sex were not consistently found to be associated with an observed PLF at tympanotomy.

Adolescent↗
PubMed1986

Diagnosis and treatment of perilymph fistulas without hearing loss.

In 1978, I reported on the diagnostic criteria and therapy based on the treatment of 34 cases of perilymph fistula. Of that group, 20 patients had no hearing loss associated with the fistula. Since that time, an additional 30 cases of fistula--15 without hearing loss--have been seen and treated operatively. The 30 significant variables of history and physical findings identified in the first study were statistically reviewed, along with a new finding that seems highly significant. Twenty-three of the 26 new cases so evaluated had a positive "eyes-closed turning test" (staggering when turning to the side of the lesion after walking with eyes closed). A further finding has been the presence of an abnormally placed round window membrane, in most cases involving the round window. The total operative population of fistulas, both those with and without hearing loss, is reviewed to identify the operative technique best suited for each window and the graft material most likely to succeed. Perichondrium is the choice tissue for graft material, except for very small fistulas at the annular ligament. The graft must be held firmly in place, with either a prosthesis or appropriate packing, carefully avoiding adhesions between the round window and the tympanic membrane.

Adolescent↗
PubMed1986

Results of surgical repair of inapparent perilymph fistulas.

In patients who are thought to have a perilymph (PL) fistula, careful inspection of the round and oval windows during exploratory tympanotomy may be normal. The decision must then be made either to terminate the procedure--knowing that the patient's symptoms will probably continue or deteriorate--or to repair both windows as if PL fistulas were present, risking further damage to the inner ear. From a series of 14 patients explored for possible PL fistulas, we report on 6 patients with preoperative diagnoses of PL fistula, based on history, physical examination, and audiometry. Symptoms resulting from trauma were present from 10 days to 23 years before surgery. During exploratory tympanotomy, no fistulas were evident; however, both the oval and round windows were repaired with tissue grafts. Follow up--for 1 to 5 years--revealed that vertigo was relieved in all patients. Postoperatively, one patient had a mild conductive hearing loss; yet no patient sustained a sensory neural hearing loss. We conclude that patch grafting of both the oval and round windows is a safe and effective method of treating suspected, but inapparent fistulas. Patient selection, surgical technique, and results shall be detailed.

Fistula↗
PubMed1987

Hydrostatic pressure measurements of endolymph and perilymph in a guinea pig model of endolymphatic hydrops.

The primary histologic correlate of Menière's disease is endolymphatic hydrops. From this, many investigators have postulated the existence of endolymphatic hypertension, although there have been no measurements published to substantiate this concept. Seventy guinea pigs, surgically treated with right endolymphatic duct obstruction, were later assessed by use of a micro-electrode technique that measured their endolabyrinthine hydrostatic pressures. For 21 of these animals, the pressures of both scala tympani (Pst) and scala media (Psm) of both ears of each animal were successfully measured. Similar measurements were made in a control group of 25 guinea pigs that had not undergone any previous surgery. For normal ears--as well as those with hydrops-pressure differences between perilymph and endolymph (Psm - Pst) varied around 0 +/- 2.0 mm Hg. When only the right (obstructed) ears were considered, there appeared to be a slight, relative pressure elevation (p less than 0.05) in scala media during the first 7 days after endolymphatic duct obstruction-and in those ears with EP, less than 70 mV. The magnitude of this pressure difference that can be attributed to the state of endolymphatic hydrops-and not to natural variability-is calculated (within 95% confidence limits) to be less than 0.5 mm Hg.

Animals↗
PubMed1987

Quantitative diagnostic test for perilymph fistulas.

Clinically, the definitive diagnosis of perilymph fistulas can only be made by tympanotomy. Results of various fistula tests based upon the vestibulo-ocular reflex have not correlated well with findings during tympanotomy. A new fistula test has been developed based upon vestibulo-spinal responses. By systematic removal of both visual and support-surface orientation references from the subject--leaving only vestibular control of postural reflexes--patients with perilymph fistulas demonstrated an increased (sometimes phase-locked) postural sway in response to sinusoidal changes in external auditory canal pressures. Results from 100 consecutively operated ears (64 patients)--77 of whom underwent preoperative and postoperative moving-platform fistula tests--indicate that the test sensitivity is 97 percent for this highly selective patient population. Absolute specificity could not be determined because, on patients without clinical indications for surgery, tympanotomy is contraindicated.

Adolescent↗
PubMed1988

The Tullio phenomenon and perilymph fistula.

Establishing the diagnosis of perilymph fistula remains a dilemma. At this time, identification of an active perilymph fistula can be confirmed only by surgery. On the basis of clinical history and audiovestibular testing, 54 patients underwent middle ear exploration for possible perilymph fistula at the Colorado Ear Clinic between July 1980 and June 1986. This group represents approximately 1% of all surgical procedures performed during that period. Seven patients (12%) were found to have the Tullio phenomenon preoperatively. Six of these were found to have active, free-flowing fistulas at the time of exploration. The presence of a Tullio phenomenon may be helpful in preoperative assessment of a patient with suspected perilymph fistula.

Acoustic Stimulation↗