Masaaki Kitahara

Experimental Study on Meniere's Disease

Experimental hydrops caused by underabsorption of endolymphatic fluid is a model of remissional stage of Menieres disease. In this study, another type of model, ie, hydrops caused by overproduction of endolymphatic fluid, was accomplished by applying various pressures into scala media through a micropipette via stria vascularis. This type of hydrops could be a model of attacks of Menieres disease. By using two types of the model, effects of glycerol administration and of opening the endolymphatic sac were discussed.

Assessment of Prognosis in Sudden Deafness

We investigated the usefulness of three-dimensional audiograms in assessing prognosis during the early phase in 116 patients with sudden deafness. The initiation time of improvement in middle-frequency hearing at 15 dB or more was valuable in assessing prognosis in patients with deafness and scale-out types of hearing loss. Improvement within 13 days in patients with the deafness type, and within 17 days in those with the scale-out type, was correlated with a high incidence of marked improvement or complete recovery. Patients with an initial mean hearing level below 80 dB, or in whom the glycerol test and electrocochleography results suggested the presence of endolymphatic hydrops, had a good hearing outcome. Patients without tinnitus showed an unfavorable hearing outcome.

Bilateral aspects of Meniere's disease. Meniere's disease with bilateral fluctuant hearing loss

Although bilateral involvement of Menieres disease is serious enough to produce deafness in both ears, actually little attention has been directed to such involvement. Recently, several reports have been made concerning the bilateral aspects of this disease (1–8). However, lacking mutual agreeable diagnostic criteria for making these reports and differences in characteristics of patients with Menieres disease among institutes makes it difficult to establish definitive interpretations. In 1988, the Vestibular Disorder Research Committee made a survey among 15 committee member institutes using the same diagnostic criteria of bilateral involvement of Menieres disease. Based on the results obtained, in this paper, incidence and characteristics of bilateral cases in Menieres disease will be discussed.

Treatment of Ménière’s Disease with Isosorbide

The effects of isosorbide – a dehydric alcohol formed by the abstraction of two molecules of water from one of sorbitol – on Meniere’s disease were examined, first using a model and then clinically. (

Swimming Test for Evaluating Vestibular Function in Guinea Pigs

A swimming test was used to evaluate vestibular function in guinea pigs. We first observed tracings of the swimming patterns of 20 healthy guinea pigs to establish the normal range. Then the same test was used in a group of 49 guinea pigs with endolymphatic hydrops induced by immunologic techniques. They did not show spontaneous nystagmus or body deviation while walking, but a total of 20 out of 49 animals displayed abnormal swimming patterns, with 8 swimming clockwise and 4 counterclockwise. This swimming test is easily able to detect mild vestibular dysfunction in guinea pigs, and can be repeated, so that we consider it useful for examining vestibular function in these animals.

Computerized Tomography of the Petrous Bone in Meniere's Disease

High resolution transverse axial computerized tomograph (CT) encompassing the lateral semicircular canal (LSC) was used to measure the size of the petrous bone in ears with bilateral (n = 13) and unilateral (n = 38) Menières disease, and in ears with unilateral chronic otitis media (n = 25) as a control group. Measurements were made of the following 4 distances in the petrous bone; A: the distance between the posterior semicircular canal (PSC) and the posterior petrous surface (PPS) (P-P distance), B: the distance between the PSC and the LSC (P-L distance), C: the distance between the vestibule and the PPS (V-P distance), and D: the distance between the PSC and the anterior margin of the sigmoid sinus (P-S distance). The P-P and the V-P distances were significantly shorter in ears with Menières disease, especially in ears with bilateral Menières disease compared to the nonaffected ears in unilateral Menières disease or ears with chronic otitis media. This tendency was clearer in the P-P distance than in the V-P distance. The P-L and P-S distances did not show any statistical difference between groups. The results indicate that bone development between the PSC and the PPS and between the vestibule and the PPS, which usually contains the endolymphatic duct and sac, is significantly poorer in ears with Menières disease than in ears with chronic otitis media. Hypoplasia of the retrolabyrinthine region may be an important factor in the pathogenesis of endolymphatic hydrops.

Electron Microscopic Studies of the Endolymphatic Sac in Ménière’s Disease

Five specimens of the endolymphatic sac taken from patients with Ménières disease during epidural drainage surgery were examined under the electron microscope. The clinical history and histopathological findings are presented. The most common and prominent finding was perisaccular fibrosis of the endolymphatic sac which appears to disturb the free absorption of endolymph in the endolymph in the endolymphatic sac resulting in endolymphatic hydrops. Well-preserved epithelial cells of the endolymphatic sac could only be found in one of the specimens.

The Influence of Vestibular and Cochlear Aqueducts on Vestibular Response to Middle Ear Pressure Changes in Guinea Pigs

The responses of primary vestibular neurons and perilymphatic pressure changes to middle ear pressure were investigated in guinea pigs with obstructed vestibular or cochlear aqueduct (closed VA or closed CA group) in order to clarify the influence of VA and CA on pressure-induced vestibular response. Although the neural response rates and the amount of perilymphatic pressure change in the closed VA group resembled those in the control group, these values in the closed CA group were higher than in the control group. Patency of the CA had a more significant effect on the vestibular response to middle ear pressure change than patency of the VA.

The influence of middle ear pressure changes on the primary vestibular neurons in guinea pigs.

The responses of primary vestibular neurons and perilymphatic pressure changes to middle ear pressure stimuli in guinea pigs were investigated in order to clarify the direct effects of pressure stimulus on the vestibular apparatus. The vestibular response was related to the amount of middle ear pressure change applied at a rate of +/- 100 mmH2O/s. The neural response rates of vestibular units to positive pressure in the middle ear were significantly larger than those to negative pressure. The time course pattern of the perilymphatic pressure change resembled that of the response of the vestibular units, indicating that the vestibular response is elicited by middle ear pressure via the pressure transmitted in the inner ear.

A Ventilation Capacity Test for the Eustachian Tube Using a Soundproof Pressure Chamber

Using a soundproof pressure chamber, we performed Békésy air conduction audiometry at 1000 Hz under the following pressure conditions: 1) from atmospheric pressure (AP) to 200 mmH2O below AP, 2) AP to 200 mmH2O above AP, 3) AP to 700 mmH2O below AP, and 4) AP to 700 mmH2O above AP. In conditions 1) and 2), the patient was instructed not to swallow until the pressure change was complete, then to swallow once every 15 seconds. The number of swallows required for hearing to return to the baseline level was counted. In conditions 3) and 4), the patient was told to swallow as many times as possible both before and after completion of the pressure change; maximum hearing level and the time needed for return to the baseline level were measured. Although all except one of the seven patients with suspected tubal dysfunction showed normal results with catheter insufflation and tympanometry, six of the seven showed abnormality and one reported the disappearance of ear stuffiness after the ventilation capacity test. We concluded that this test is useful not only for the diagnosis of tubal dysfunction but also as a possible therapy for aiding adaptation to changing environmental pressure.