Jin Okubo

Epidemiological Studies on Benign Paroxysmal Positional Vertigo in Japan

In 1980, the Research Committee of Peripheral Vestibular Disorders in Japan, which is supported by the Ministry of Health and Welfare, was founded by 24 members, from several districts in Japan. The Committees first task was to draft the diagnostic criteria for several peripheral vestibular disorders, such as benign paroxysmal positional vertigo (BPPV), and vestibular neuronitis. For the national epidemiological survey, they then collected the data on 101 cases of BPPV out of some 783 vestibular disorder patients. In addition, data on 103 patients of BPPV out of 559 vestibular disorder patients were also collected from the Neuro-otological Clinic of the Toyama Medical and Pharmaceutical University Hospital. From these epidemiological surveys, the incidence of BPPV in Japan was estimated at 10.7 per 100,000 population, while that of BPPV in Toyama was estimated at 17.3 per 100,000 population. The ratio of BPPV was higher in female than male patients in both surveys. The age at the onset of BPPV peaked in the fourth decade in both males and females. Compared with the other epidemiological features of Menieres disease and sudden deafness with vertigo in the same surveys, it appeared that the characteristic features of BPPV are epidemiologically similar to those of Menieres disease, but different from those of sudden deafness.

Sonotubometric Measurement of the Eustachian Tube Function by Means of Band Noise

The Eustachian tube is well known as an organ serving the ventilation and drainage of the tympanic cavity and mastoid. Ventilation is carried out by the opening and closing of the Eustachian tube accompanying swallowing movements. Until now there has been no instrument to quantify these motor activities of the tube necessary for its function as a ventilator. The author developed a generally applicable sonotubometer Model WIO-01 with the help of Siemens Hearing Institute K.K. for automatic measurement of the aforesaid tubal function with the use of 7 kHz full-octave band noise. In a sonotubometric trial with 32 adult female subjects, the duration of patency of the Eustachian tube was 288.5 +/- 1.38.5 ms, and the amplitude eliciting response was 16.4 +/- 8.3 dB. The positive response rate was 89.1%. In 89 children aged 4-12 years, a positive response was detected in 117 ears (61.9%). The mean duration of patency was 337.7 +/- 154.4 ms, and the amplitude 16.3 +/- 7.2 dB. It is physiological to have tubal opening and closing during natural swallowing. It is therefore important to understand the tubal function when dealing with tympanoplasty and diseases caused by tubal dysfunction.

Physiology and Pathophysiology of Air-Filled Ear Space and Eustachian Tube Function

The function of the Eustachian tube under atmospheric pressure, on the grounds of our studies, is discussed as follows: (1) Criteria of natural valvular function of the auditory tube under a normal pressure environment. (2) Opening action of the Eustachian tube and mode of swallowing movement in comparison with soft palate movement. (3) High pressure environment and (opening action of) Eustachian tube. (4) Children undergoing tubing and their Eustachian tube function. (5) Ventilatory function of the Eustachian tube under normal pressure conditions. (6) Factors influencing changes in pressure in the tympanic cavity.

Aeration of the tympanomastoid cavity and the Eustachian tube.

Physiological changes in body position affect the degree of opening and closing of human auditory tubes. Notable changes were observed in lateral body position concerning the opening rate of the auditory tubes, which corresponds to the changes in pressure within the lower portion of the middle ear cavity. This physiological mechanism seems to be related with the anatomical direction of the auditory tube and the natural mechanism for the protection of the middle ear cavity. When a change takes place which moves the compliance of the eardrum to the positive side (e.g. head position change or static lateral body position), observation suggests the possibility of venostatis and production of gas. Measurement of the oxygen tension in the middle ear cavity under atmospheric pressure revealed the existence of constant gas production which maintains the pressure in the middle ear cavity at the same level as atmospheric pressure. This result denies the influx of gas from the atmospheric environment into the middle ear cavity. These results stem from the intrinsic physiologic mechanism of the middle ear cavity, namely maintenance of effective auditory sound conduction (a function to keep eardrum compliance as close to zero as possible), by keeping the pressure within the middle ear cavity below the atmospheric pressure, either at the same level as or slightly higher than that of the environment pressure. Gas emission from the middle ear cavity in the atmospheric environment and a low oxygen tension are a natural physiologic mechanism to protect the middle ear cavity from infection and other hazards.

The influence of eye movements and tactile information on postural sway in patients with peripheral vestibular lesions.

The statokinesigram of the 16 benign paroxysmal positional vertigo (BPPV) patients and the 28 vestibular deficits (VDS) patients were analyzed in comparison with the 20 normal subjects (NS). Velocity of the track (LNG/T), root mean square (RMS), and standard deviation area (SD-Area) were used as parameters. Fourteen different tests were done. When the result for each subject group were analyzed there were interesting differences between the compensated VDS and BPPV patients and between the untreated period and the compensated stage in each patient group. Comparing the data between NS and BPPV at the compensated stage, the latter group was unstable while watching LED with OKN on the tactile information plate (S-G plate). The significant differences were for RMS and SD-Area. The data of the NS and the untreated VDS show that the latter group was more unstable while watching LED with OKN than in the dark on the S-G plate. According to the data of the NS and the VDS at the compensated stage, the latter group was more unstable during OKN or watching LED which was almost the same as in the dark on both plate conditions. And it was more unstable while watching LED than during OKN on the S-G plate. The significant differences were for velocity of body sway (LNG/T). The neural region for compensation in BPPV patients might be on the visuo-oculomotor pathway through the peripheral retina. One of the most important regions for compensation in VDS patients might be in the rombencephalic reticular formation.

Barotraumatic Perilymphatic Fistula and Tympanometry in Lateral Position.

The presence of a perilymphatic fistula has been difficult to determine because of the lack of efficient and reliable testing methods. The condition is suspected on the basis of the history alone and is confirmed by surgery.Our previous studies have shown that when a patient with mild dysfunction of the eustachian tube lies on his side, the lower middle ear cavity pressure becomes markedly positive.It is important to differentiate perilymphatic fistula (PLF) from other inner ear disease, and the purpose of this study was to clarify by positional tympanometry mild dysfunction of the eustachian tube with barotraumatic PLF.Using the peak values of the tympanogram in the lateral position (TLP), we analyzed the changes in pressure of the lower tympanomastoid cavity in ears with PLF and in patients with sudden deafness.In patients with PLF, there was a significant increase in the internal pressure of the affected lower cavity, which rose to 81.0±4.4 mmH2O after 10 min (Nor. 27.7±16.8 mmH2O). On the other hand, in patients with sudden deafness, middle ear pressure was 24.13±8.00mmH2O after 10 min.These results suggest that when there is a strong possibility of barotraumatic PLF, we can utilize TLP for the diagnosis of PLF. Once there is a marked elevation of the affected ear cavity pressure in TLP, exploratory tympanotomy must be done immediately.

Sonometric auditory tubal function test for evaluation of children with otitis media with effusion.

The present study investigated the eustachian tube function in children with otitis media with effusion (OME) and also evaluated the effectiveness of adenoidectomy in such patients. The subjects consisted of 32 children with OME, all of whom underwent tube insertion and adenoidectomy, resulting in an improved hearing level to a range of 0-10dB. Sonometric auditory function test was carried out on the patients whose tube was in place and the middle ear was well aerated. Normal transmission of sound was observed in 71.4% of these children. However, it was seen in only 2% of the children not surgically treated. Satisfactory tubal function was noted in patients whose ventilation tubes remained in place for a period of 250 days or longer. It is, therefor, suggested that the optimal timing of tube extraction should be approximately eight months post-operatively, at which time the eustachian tube appears to tart functioning well.Our second study measured intranasal pressure in children with OME when they performed Toynbees manuever. Some children were treated with adenoidectomy with tube insertion and the others were not surgically treated, and the results were 5.66±2.92mm H2O and 3.93±1.79mm H2O, respectively. A significantly high intranasal pressure seen in patients with OME who had undergone adenoidectomy seems to account for the effective nasopharyngeal closure that had occurred as a result of improved movement of the soft palate including the levator veli palatine muscle. From these findings, it was concluded that adenoidectomy facilitates opening the tubal lumen by the tensor veli palatine muscle.

Hyperbaric therapy of otitis media in children.

Secretory otitis media occurs most frequently in infancy. Since the Eustachian tube functions differently in children and adults, it is considered unlikely that secretory otitis media in the two age groups is due to the same cause. Since the infantile Eustachian tube is a kind of pressure open type, we preffered high-pressure therapy in the treatment of secretory otitis media in children.We used high-pressure therapy for 111 children aged 3 to 12 years 188 ears) with secretory otitis media. As a result, 129 ears(68.6%)showed improved average hearing levels within 10 dB in the low, medium, and high tone ranges. No patient experienced earache or other trouble when exposed to high-pressures. In the highpressure therapy, air escapes through the Eustachian tube when the middle ear pressure is regulated. In this case, the fluid can be excreted together with the air. Since the partial pressure of oxgen rises with the pressure, it is estimated that the highpressure therapy favorably affects ciliary movement and restores the mucous menbranes in the tympanic cavity and the Eustachian tube.

A posturological study of pseudofistular sign in normal adults and Meniere's patients

A new stabilographical method with pressure loading to the external auditory canal (PLT) was performed in 20 normal subjects and 3 patients with Menieres disease for the purpose of testing the pseudofistular sign. The pressure ranging from -100mmH2O to +100mmH2O or from -200mmH20 to +200mmH2O were applied to the external auditory canal and the body sways of the center of gravity to the lateral directions for 10 seconds were summated 10 times by a signalprocessor (NEC-sanei, 7TO7A). Positive response was defined as having doubles sway amplitude compaired with the average amplitude of sway without pressure loading.Positive response were observed in seven of twenty normal subjects. These positive reactions were symmetrical in both ears except one case. On the other hand, in cases of Menieres disease, positive responses were found only in the affected ears. The positive PLT response was not changed at all when the test was repeated in a case of Menieres disease at the stage of positive response to the grycerol test, however, in another case of Menieres disease, disappearance of positive PLT response was observed after the puncture of the eardrum.From these findings we considered that the most effective facter of the PLT in producing the deviation was not the pressure change of the middle ear, but the movement of the ossicular chain causing displacement of the foot-plate of stapes.

Correlation between Personality and Vestibular Dysfunction

Among 1300 patient with vestibular dysfunction surveyed epidemiologically, 843 were analysed as to personality type with disorder reference to vestibular and to subjective vertigo.(A) Correlation between Disease and Personality1) Few patients had a strong-minded or strong-willed personality.2) Strong-willed personality was apt to be present in patients suffering from traumatic dysfunction of the vestibular system.3) A social personality traits were often found in patients suffering from true Menieres disease, suspected Menieres disease, and advanced bilateralvestibular dysfunction.(B) Correlation between Subjective Vertigo and Personality1) In general, no differences in degree of subjective vertigo were observed among patients with different personality traits.