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PubMed1981

Steep gradients of amino acids between cochlear endolymph and perilymph.

Levels of 19 free amino acids in cochlear endolymph and perilymph of scala vestibuli of the guinea pig were determined using reverse phase high performance liquid chromatography (HPLC) of the o-phthaldialdehyde-ethanethiol derivatives with fluorescence detection. Aspartate and glutamate were found to be significantly higher in endolymph than in perilymph, confirming results from another study using a different analytical method. The remaining 17 amino acids were significantly lower in the endolymph, in many cases by an order of magnitude. The data are compared with results on utricular endolymph and vestibular perilymph obtained by HPLC in another study from our laboratory. Possible implications and interpretations of the results are discussed.

Amino Acids↗
PubMed1982

Arguments against a mediating role of the adenylate cyclase--cyclic AMP system in the ototoxic action of loop diuretics.

Previous studies in our laboratory have indicated that adenylate cyclase of the stria vascularis is strongly inhibited in vitro by ethacrynic acid and furosemide. In order to test whether the in vitro effects upon the enzyme are also present under in vivo conditions, ethacrynic acid was perfused perilymphatically for 15 min and 20 min at a concentration of 10(-3) M. Cyclic AMP of the stria vascularis was reduced by 27% and 34%, respectively, but ATP also declined significantly, suggesting unspecific effects. When ethacrynic acid was applied intravenously at a dosage of 50 mg/kg, and the endolymphatic potential allowed to decline to -10mV, no significant changes in cyclic AMP and ATP were seen. The absence of effects upon cyclic AMP in the early stage of systemic intoxication with ethacrynic acid is strong evidence against a mediating role of adenylate cyclase in the ototoxic action of ethacrynic acid. When a bolus of 3 x 10(-2) M furosemide was applied intra-arterially the endolymphatic potential declined at the exceedingly rapid rate of about 10 mV/sec, strongly suggesting that the action of the drug takes place in the vicinity of the capillaries of the stria vascularis. In view of the proposition that adenylate cyclase appears to be located primarily at eh luminal aspect of the stria vascularis, this constitutes further evidence against a role of the enzyme in the mediation of the specific ototoxic effects of loop diuretics. Other recent evidence against a mediatory role of the adenylate cyclase--cyclic AMP system is discussed.

Adenosine Triphosphate↗
PubMed1983

Hydrops following perilymph fistula repair.

A series of 15 ears were explored for perilymph fistulas. Fifteen fistulas were found in 13 ears. Two cases are presented which developed hydrops-like symptoms only after closure of their fistulas. Closure of the other patients' fistulas was successful in relieving vertiginous symptoms, although hearing seldom improved. There were no significant complications of surgery. Fat failed as a graft material 4 of 10 times, whereas vein and perichondrium were not associated with recurrence of symptoms. The ENG-fistula test, as described by Daspit and associates, correctly predicted the presence or absence of a fistula in 7 of 8 ears tested. Hennebert's sign correctly predicted fistulae in 2 ears, and Hennebert's symptom was associated with proven fistulae in 9 of the 10 times it was present. Because of the low morbidity and the high success rate of surgery, a patient with a history suggestive of a perilymph fistula should have exploratory tympanotomy, particularly if the ENG-fistula test is positive.

Adult↗
PubMed1986

Perilymph fistula: the Iowa experience.

Ninety-one patients with demonstrable perilymph fistulas presented with an amazing array of signs and symptoms ranging from unilateral tinnitus and aural fullness to sudden-and-profound hearing loss, roaring tinnitus, and whirling vertigo. Between 1977 and 1984, 214 exploratory tympanotomies for suspected perilymph fistula (PLF) were performed on 177 patients. One hundred six primary (initial) fistulas were found in 95 ears and 26 recurrent fistulas were identified. Eighty-two percent of the 91 patients with PLF had auditory symptoms, 8% with auditory symptoms as the sole complaint. Eighty-one percent of the patients had vestibular symptoms, 12% with vestibular symptoms alone. The type of hearing loss and the nature of the vestibular symptoms were widely variable. Of the 58 patients with preoperative auditory symptoms, 49% had improved hearing (23% improved to serviceable range), after closure of PLFs. Ninety-five percent of the patients who presented with vestibular symptoms had elimination of or decrease in their dizziness to the extent that it no longer interfered with their daily activities. The highest incidence of recurrent fistula was associated with grafts using fatty tissue. Patients with Mondini deformity were at particularly high risk for fistula recurrence.

Adolescent↗
PubMed1986

Perilymphatic fistulas: are they exclusive to the round and oval windows?

Eleven patients suspected of having perilymphatic fistulas were evaluated. A perilymphatic fistula was demonstrable in ten of these patients. In six patients, fistulas of one of the windows, or both were found. In two patients, combined fistulas of both the round window and lateral semicircular canal were found. In two other patients, fistulas were found only in the lateral semicircular canal. The patients in whom fistulas were found and repaired improved dramatically. The patient without a demonstrable fistula remained symptomatic. We have shown that perilymphatic fistulas can occur in the lateral semicircular canal, and suggest exploring this area when indicated.

Adult↗
PubMed1986

Two emerging perilymph fistula "syndromes" in children.

This paper proposes two relatively common "syndromes" seen in children with perilymph fistulas using illustrative case reports. One, a 2 1/2-year-old child with bilaterally symmetric progressive sensorineural hearing loss, was found to have bilateral oval and round window fistulas. The other was a child who presented originally with an unexplained unilateral sensorineural loss. It was only when hearing deteriorated in the opposite ear several years later that a perilymph fistula was suspected and confirmed by tympanotomy. The clinical presentations and other details of these cases diverge widely, but may represent two emerging syndromes of perilymph fistulas in children: 1. a congenital or hereditary predisposition, and the other, 2. sudden hearing loss in the "good" ear of children with an unexplained sensorineural hearing loss in the opposite ear.

Audiometry↗
PubMed1988

Vestibular function in experimental endolymphatic hydrops.

Endolymphatic sac ablation in the guinea pig can result in a dilated membranous labyrinth and low-frequency hearing loss similar to patients with Meniere's disease. However, this animal model fails to develop analogous symptoms of a Meniere's crisis such as sudden hearing loss and marked vestibular imbalance. Possibly, factors in addition to endolymphatic hydrops must be present to result in a crisis episode. By placing animals in an inverted posture, their intralabyrinthine pressure was elevated, causing additional stress on the inner ears. Standard electronystagmographic techniques were used to monitor vestibular imbalance, which appeared as spontaneous nystagmus in the dark. Nineteen of 23 animals with unilateral endolymphatic hydrops showed spontaneous nystagmus in an inverted posture. Physiologic mechanisms explaining these results are described.

Animals↗
PubMed1988

Perilymphatic fistula in children with preexisting sensorineural hearing loss.

Progression of preexisting sensorineural hearing loss (SNHL) in infants and children has been considered an indication for fistula exploration: is this approach warranted? On exploring 36 middle ears in 26 such children, we found a perilymphatic fistula (PLF) in four ears (11%). Although there was radiographic evidence of inner-ear deformity in one half of these children, a definite fistula was found in only four of 18 radiographically abnormal ears explored (22%). Even in the four patients with a history of an "event" that could implicate a fistula such as exertion or barotrauma, a fistula was found in only one. There are a number of possible causes for progression of a preexisting SNHL, and surgical exploration of the middle ear should not be recommended on the basis of progression alone. Instead, exploration for a suspected PLF should be strongly considered when there is also a history of an "event", and/or radiographic evidence of inner-ear abnormalities. Even under these conditions, one should be aware that fistulae are not likely to be found.

Adolescent↗
PubMed1989

Theoretical and practical implications for plasmapheresis in autoimmune inner ear disease.

Immune-mediated inner ear disease, by convention called autoimmune inner ear disease (AIED), has established clinical profile guidelines for diagnosis. Treatment consists of steroid and/or cytotoxic drug immunosuppression. The role of plasmapheresis (PMP) in the treatment of AIED has not been defined. Lack of a precise serological marker prevents accurate immunological understanding. Definition is, of course, difficult in a disease whose natural history is not well delineated. Successful use of PMP in one steroid and cytotoxic drug intolerant patient with AIED led to its use in a total of eight patients. The rationale for PMP was based on its known effectiveness in other autoimmune diseases and thus, its potential use in AIED. Improved auditory function occurred in 6 of the 8 patients, 3 of whom have been followed for over 3 years. Three of the six no longer require immunosuppressant medication. PMP can be used as an alternative or adjunctive therapy in AIED. These preliminary results suggest PMP can stabilize or improve auditory and vestibular symptoms in selected patients. Its use as a first line therapy followed by cytotoxic immunosuppressants bears consideration.

Adult↗
PubMed1990

Early alterations of cochlear function in experimental perilymph fistulas.

Alterations of cochlear function secondary to perforation of the round window membrane in guinea pigs were expected to reveal sensitive and/or specific audiometric parameters in perilymph fistulas. A perforation of the round window membrane either did not affect acoustic compound action potential thresholds, or induced a delayed, possibly conductive, inner ear hearing loss. Also, evoked suprathreshold responses deteriorated progressively and independently of the increase of compound action potential thresholds. A sudden (conductive) hearing loss and a poor response to suprathreshold stimulation might indicate inner ear damage secondary to a perilymphatic fistula.

Animals↗