The effect of hyperosmotic solutions in Meniere's disease was studied by the hydrogen (H2) clearance method. The procedures used in this experiment were nearly the same as those described in chapters 1 and 2. To examine the turnover rate of perilymph, the cochlear aqueduct was obstructed and perilymphatic H2 clearance was measured before and after glycerol infusion. Guinea pigs were divided into group A, in which the cochlear aqueduct was obstructed and group B, untreated controls. H2 clearance was measured for 10 minutes before and for 10 minutes after the infusion of glycerol. The half life of H2 clearance in the perilymph of group B was significantly reduced after glycerol infusion, as described in chapter 2. Shortening of the half life after glycerol infusion was significantly less marked after obstruction of the cochlear aqueduct. These results suggest that temporary improvement of hearing after glycerol administration in patients with Meniere's disease is due to an increased turnover rate of perilymph. The excess potassium in the perilymph must be washed out not only by increased blood flow but also by an increased turnover rate of the perilymph through the cochlear aqueduct. Hearing is probably improved by normalization of the postassium level in the perilymph.
We have reported that middle ear pressure changes influenced vestibular nerve activity. In the present study the influence of middle ear pressure on the lateral vestibular nucleus neurons was investigated in anesthetized cats. The activities of the lateral vestibular nucleus neurons, especially the lateral vestibulo-spinal tract neurons, were recorded extracellularly. Positive or negative pressure was applied to the middle ear cavity bilaterally through perforation of the tympanic membrane. In most lateral vestibular nucleus neurons firings were increased with negative pressure and decreased with positive pressure. These effects were more prominent when pressure changes were applied to the contralateral middle ear cavity. These influences of middle ear pressure on the lateral vestibular nucleus neurons were opposite to those on the vestibular nerve, and the existence of inhibitory interneurons was considered.
The effect of different head positions on vestibulo-spinal reflexes was investigated by measuring the activities of the soleus and tibialis anterior muscles induced by galvanic stimulation of the labyrinth (labyrinthine evoked EMG). A subject was asked to stand with eyes closed and was stimulated with a galvanic current by a bipolarbiaural method with the cathode on the right ear and the anode on the left ear. The intensity was 1 mA and the duration was 3 s. The evoked EMG was observed with the head facing foward and the head turned to the left and right at angles of 30°, 45° and 90°. 1. With the head facing forward, soleus muscle activities increased on the right side and decreased on the left side. The potential changes of the tibialis anterior muscle varied with the individual subject. 2. When the head was turned to the right at an angle of 30°, soleus muscle activities increased on the right side and decreased on the left side, but the potential changes of both soleus muscles were smaller than when the head was facing foward. Tibialis anterior muscle activities increased on the right side and decreased on the left side. 3. When the head was turned to the right at an angle of 45°, both soleus muscle activities decreased and tibialis anterior muscle activities increased on the right side and decreased on the left side. The potential changes of the soleus muscle on the right side were opposite to those when the angle was 30°. 4. When the head was turned to the right at an angle of 90°, both soleus muscle activities decreased and both tibialis anterior muscle activities increased. 5. The evoked potentials with the head turned to the left at angles of 30°, 45°, and 90° were usually opposite to those when the head was turned to the right. 6. The vestibulospinal responses induced by galvanic stimulation indicated sequential changes corresponding to the angle of rotation of the head. The vestibular system produces spinal reflexes after processing information transmitted from the neck proprioceptors.
The effect of etizolam, a thienodiazepine, was compared with that of a placebo in a double-blind controlled study of patients with vertigo. 1) The final global improvement rate in the etizolam group was moderate to excellent in 52.4%, and slight to excellent in 81.0%. The final global improvement rate in the placebo group was excellent in 18.8% and slight to excellent in 56.3%, and worsening of vertigo occurred in 12.5 % of the placebo group. The difference between the two groups are significant. 2) Etizolam was significantly more effective than placebo in treating patients with anxiety. 3) Etizolam was significantly more effective than placebo for non-rotatory vertigo in the first and second weeks of treatment. 4) Side-effects were observed in 12.5% of the etizolam group and in 25.0% of the placebo group, not a significant difference. None of the side-effects were severe. 5) The global utility rate of etizolam was significantly greater than that of placebo.
In three children with inner ear anomalies revealed by temporal bone CT, the results of vestibular function tests were correlated with the development of gross motor and balance functions. The temporal bone CT showed cystic semicircular canals and otolithic organs in these three children. The vestibulo-ocular reflex was examined by the caloric test, the damped-rotation test, electronystagmography, and the counter rolling test. The development of balance funtion was assessed by computerized stabilometry, and neurological tests such as standing on one foot, simulating an airplane, Mann's test, the stepping test, walking on a blance beam with eyes open and eyes closed. The development of gross motor function was retrospectively checked on the basis of eight items, such as head control, standing and walking. 1) The caloric test showed no response to ice water irrigation in any of the three children. The damped-rotation test elicited normal perrotatory nystagmus in cases 1 and 2 and hypoactive perrotatory nystagmus in case 3. Post-rotatory nystagmus was absent in all three. 2) Assessment of balance function by stabilometry and neurological examination revealed a mild delay. However, follow-up examination 3 years later showed normal balance function in all three. These indicate that children with inner ear anomalies have delayed development of gross motor and balance functions, but that these become normal with time.
We tested the applicability of all-purpose software to programs of analyzing ENG and found it as useful as custom-made programs in the following aspects : 1. artifact elimination ; 2. number analysis of the nystagmus ; 3. measurement of the velocity and amplitude of the slow-phase ; 4. determination of the fast-phase velocity ; 5. demonstration of eyemovements in relation to the movement of the gaze target in the ETT test. Although some problems such as on-line processing are left unsolved, this system of analysis assures cost effectiveness and adjustability for each researcher's purposes. It is a valuable resaerch tool.
As a clinical test of the interactions between the optokinetic and vestibular systems, a new test of optokinetic nystagmus elicited by pendular stimuli (P-OKN test) was developed and carried out in 194 patients with central nervous system disorders and compared with the OKN test by linear acceleration stimuli. Most patients with central nervous system disorders with decreased P-OKN gain showed diminution of OKN during linear acceleration. However, in several cases, normal P-OKN accompanied, by abnormal accelerated OKN and/or abnormal P-OKN accompanied by normal accelerated OKN findings were observed. We concluded that the difference between the P-OKN and the accelerated OKN tests may be associated with different alertness during the optokinetic stimuli, especially due to the short stimulation time and also the increased and decreased velocities respectively. Moreover, the difference between look nystagmus and stare nystagmus may be involved. The P-OKN test is a simple and useful short test for detecting abnormalities of oculomotor system, and may become a good screening and follow-up test for central nervous system disorders.
The Quix test, named for F. H. Quix, is useful test for determining vestibular lesions. We usually perform this test with the patient standing in front of a graph paper, feet slightly apart and arms outstretched with index fingers extended. The examiner marks the points touched by the tips of the index fingers. The patient is then requested to close his eyes for one minute, and the index fingers are observed for drift. We performed the Quix test, the stepping test and the gait test in 260 patients with vestibular and auditory disorders and the results were compared with the results of the caloric test. These three tests were considered to have similar validity as preliminary tests for determining the side of the vestibular lesion.
Neuro-vascular compression of the eighth cranial nerve was diagnosed in four patients. They all had had intractable vertigo, tinnitus and hearing impairment for several years, and had been treated for Meniere's disease without improvement. Three of them were operated on, and relieved of vertigo. Air-CT scans were very useful in making the diagnoses.
An acoustic neurinoma was found in a patient with a chronic floating sensation and abnormal sensation around the left eye but little hearing impairment. A 49-year-old woman had complained for 6 years of a floating sensation and tinnitus on the left. Because her floating sensation gradually worsened she visited our clinic. Neurotological findings were as follows : persistent right-beating nystagmus in each test of spontaneous nystagmus, positional nystagmus and positioning nystagmus, and the absence of a caloric response on the left. Pure tone audiograms revealed a slight sensori-neural hearing loss with an average of 26 dB. Auditory brainstem responses showed that the I -V interpeak latency interval was prolonged. CT and MRI disclosed a mass in the left cerebellopontine angle. An acoustic neurinoma in the left cerebellopontine angle was removed by neurosurgeons. Specimens from the tumor showed characteristic features of schwannoma (Antoni B type). The postoperative course was almost uneventful, but tinnitus remained on the left. The literature is reviewed. We emphasize that a longer neurotological follow-up is needed in patients complaining of a floating sensation and tinnitus, even if the hearing impairment is slight, as in this patient. Moreover, ABR is desirable in the diagnostic evaluation of acoustic neurinoma.
The righting reflex is essential for the maintenance of equilibrium, functioning to maitain the head and trunk in a state of balance with regard to gravity. Since patients suffering from vestibular disorders almost always complain of dizziness during such everyday movements as rising and walking, the righting reflex should be evaluated within the context of the above dynamic state. A new method of acceleration registrography was designed to enable the testing of this reflex in subjects standing on a moving platform. Subjects stood blindfolded on the tilt platform, which was arranged to slope automatically to the right and left. The subjects were requested to maintain their heads in a vertical position and return the board to the horizontal position with a handheld electrical switch. During this time the tilt angle of the support platform and side to side acceleration of the head were measured simultaneously. Participating in the study were 49 normal controls and 80 patients with peripheral vestibular disorders. “Average amplitude of head sway”, one of the indicators measured, proved to be significantly larger in cases of peripheral vestibular disorders than in the controls. “Average head position” also deviated significantly from normal in patients with peripheral vestibular disorders, with 46 % showing difficulty in returning their heads to the vertical position ; of these, 79 % experienced such difficulty when the platform tilted in the direction of the diseased ear. Currently used righting reflex and deviation tests, such as Romberg's test, Mann's test, and the stepping test were less successful in detecting such a high incidence on the diseased side. The test we devised thus appears to be more sensitive for measuring the labyrinthine righting reflex function and to represent more accurately the disequilibrium and/or dizziness experienced in everyday life.
The Schellong test and ECG R-R interval test were performed along with other otoneurological examinations in 33 patients with spinocerebellar degeneration and five with Shy-Drager syndrome. Of the 33 patients 21 (63.3 %) had a positive Schellong test, 8 (44.4%) a positive static R-R interval test and 15 (83.3%) a positive dynamic R-R interval test. In our series abnormalities were observed in patients not only with OPCA, which is supposed to have a pathological relationship to Shy-Drager syndrome, but also in those with LCCA or miscellaneous type. There was a higher incidence of blood pressure and heart rate dysautonomia than difficulty in micturition. Patients with Shy-Drager syndrome had severe dysautonomia in each evaluation. There was no significant relationship between the results of dysautonomia and smooth pursuit and FFS (failure of fixation suppression) which showed great variations of degeneration of neural systems in each case. Only a few patients with dysautonomia complained of dizziness and black-out sensation. This is supposed to be one of the characteristics differences from Shy-Drager syndrome. The Schellong test and the computer-analyzed ECG R-R interval test are of great importance in evaluating the clinical features.