In order to find out how otologists contribute to the diagnosis of acoustic neurinoma, a questionnaire was sent to 80 neurosurgical departments of university hospitals. Answers were obtained from 71 departments. 1) Acoustic neurinomas represented 7.8% of all brain tumors in Japan. The rate varied from 0% to 24% in university hospitals. 2) 48.8% of acoustic neurinomas were diagnosed by otologists. The rate varied from 0% to 100% in university hospitals. Since in most cases, the first symptom of acoustic neurinoma is unilateal progressive hearing loss, it was presumed that more than 48.8% of acoustic neurinoma patients had visited an otologist's clinic. In order to prevent wrong diagnosis, problems which frequently rise in diagnosing acoustic neurinomas are discussed.
It has been reported that reticular formation neurons in the brain stem and pons play important roles in the regulation of rapid eye movements. The present paper describes the roles of brain stem reticular neurons, such as pause neurons (PN), inhibitory burst neurons (IBN) and excitatory burst neurons (EBN) in cats. These reticular neurons, including vestibular nucleus neurons, make a feedback loop and regulate rapid eye movements.
We developed a new recording system of eye movement with a CCD image-sensor in a video-camera. We showed that CCD-EOG is a valuable caloric test. In comparison with caloric tests using conventional methods, caloric testing with CCD-EOG has some advantages : 1. Eye movenents can be watched on a green display, where it is easier to measure the duration of nystagmus. 2. No dark adaptation is needed in recording : change of light does not affect the recording of eye movements. 3. Quantitative analysis is easier because the data are stored on a floppy disk and the recording system is precise.
The maculo-ocular reflex related to horizontal sinusoidal linear accelerations was studied in 7 patients with labyrinthine disorders, 4 with unilateral and 3 with bilateral disturbances. 1. The responses of the patients with unilateral labyrinthine disorders were the same as those of normal human subjects. 2. Reduced responses and increased phase differences were observed in the patients with bilateral labyrinthine disorders. 3. Differences in functional vulnerability between the semicircular canals and the otolith organs were demonstrated in patients with ototoxic disorders by comparing the results of the pendural rotation test with those of the sinusoidal linear acceleration test.
Eight healthy adults were examined electro-nystagmographically to evaluate the influence of sodium amobarbital on the human vestibular system. Seven of them showed direction-changing positional nystagmus with the direction toward the lower ear in six, and toward the upper ear in one. There was no difference of mean slow phase velocity between right and left positional nystagmus. Downbeat nystagmus, horizontal and vertical gaze nystagmus, and saccadic pursuit were also observed in the supine position. We concluded that direction-changing positional nystagmus after a I.V. injection of sodium amobarbital is due mainly to its action on the central vestibular system.
In 7 of 54 patients who showed lack of holizontal caloric nystagmus with cold stimulation with the eyes closed on electronystagmography, upbeat nystagmus was recorded and became downbeat in 4 patients when their head position was changed. The severe CP of the 7 patients was considerd to be caused by lesions of the inner ear or peripheral vestibular nerve since they showed normal findings on OKN, ETT and cranial nerve testing. This upbeat caloric nystagmus seems to originate from the cold caloric stimulation of the anterior canal in patients with a lateral canal lesion, who don't show the perverted nystagmus which is believed to indicate a lesion of the vestibular nucleus. In conclusion, the vertical component of caloric nystagmus, which is nearly always upbeat with cold stimulation, appears to point to a partial lesion of the inner ear or peripheral vestibular nerve.
The frog posterior semicircular canal was stimulated sinusoidally by mechanical endolymphatic flow. The interaction of the excitatory and the inhibitory responses was analyzed on spike density histograms. When the oscillation started from the ampullofugal direction (AF), the evoked action potentials were readily suppressed by the following ampullopetal (AP) stimulus. When the oscillation started from the AP direction, the action potential appeared slowly, indicating that the inhibitory response is slower than the excitatory response.
Recent studies have shown that when normal human volunteers are subjected to a sudden free fall, EMGs of truncal and limb muscles are activated due to the startle reflex originating in the otolith organs. In this study, muscle activities during sudden free fall and voluntary fall were recorded in 18 healthy human subjects. Monophasic or biphasic EMG responses could be recorded from all subjects during sudden free fall; the average latency of initial activity was 29.2msec (SD 3.5msec) in the orbicular oculi muscle, 67.7msec (SD 9.3msec) in the anterior tibial, 73.5msec (SD 9.2msec) in the gastrocnemius and 71.8msec (SD 9.4msec) in the soleus muscles. On the other hand, such initial activities did not appear in voluntary falls, and only activity which coincided with landing could be recorded. It is suggested that free fall stimulation can be used as a diagnostic tool in disorders of otolithic function.
A mathematical model of postural control while standing upright was formulated, and the results of stabilometry in normal subjects were simulated. Three modes of postural control : position control and velocity control of the body center of gravity (CG), and control of deviation between the projection point of CG (PCG) and the center of pressure (COP) of the body weight, were postulated. Our model was represented by two differential equations : equation of motion of PCG and equation of control of the velocity of COP in the three modes of postural control mentioned above. A random stochastic variable was also introduced as a control error. Equations were solved numerically with a computer, and the results were compared with the actual data of stabilometry of normal subjects. 1) Each mode of control was indispensable for maintaining balance. 2) Among the three modes of control, velocity control and deviation control played the main roles. It was necessary to change the velocity of COP in proportion to a weighted sum of the velocity of PCG and the deviation of PCG from COP. 3) We could make the calculated drifting parameters roughly in agreement with the actual drifting parameters of the normal subjects by choosing reasonable values of model parameters. 4) Calculated drifting patterns of the COP simulating unilateral vestibular hypofunction showed a deviation toward the affected side.
A patient with Tullio's phenomenon of the right ear was tested with infrasound through the auditory canal which was generated at 100115dB SPL of 1545Hz by an ear drum massager. Nystagmus towards the right was recorded on ENG when the infrasound was produced in the right ear and it shifted to the left when the infrasound was interrupted, but no nystagmus occurred when the left ear was exposed to infrasound. In stabilometry tests the area of the stabilogram was increased significantly when infrasound was produced in the right ear, but it was normal when the left ear was exposed to infrasound. These findings were believed to be elicited by the transmission of pressure from the ossicles to the membranous labyrinth which was speculated to be distended by endolymphatic hydrops. Probe tympanotomy was performed, and no abnormality of the middle ear was noted, but the symptoms of Tullio's phenomenon disappeared postoperatively.
A patient with acute facial palsy was found to have acoustic neurinoma, which responded well to steroid therapy. The patient was a 72-year-old male who had had intermittent dizziness and slight hearing impairment on the right side for two years. One morning severe hearing loss, dizziness and otalgia occurred. On the next day, he had sudden total facial palsy on the right side. Examination revealed complete right deafness and total canal paresis, but X-rays were abnormal. Steroid therapy relieved facial palsy and dizziness, but hearing and caloric response did not improve. Four years later, his gait became gradually disturbed, and he felt an abnormal sensation on the right side of his face. CT scan showed a right cerebellopontine angle tumor (27×21mm) with cyst formation.At operation a schwannoma of the superior vestibular nerve was removed. This case demonstrates that acoustic tumor must be ruled out even when facial palsy develops suddenly.
Acquired pendular oscillations (APO) appeared when the eyes were closed and when they were open but covered. The frequency of APO was 6Hz and the amplitude about 4 degrees. Follow-up studies were performed with ENG (electronystagmography) otoneurological evaluations, and MRI. APO was suppressed when the eyes were opened, and also after the intravenous injection of thyrotropine releasing hormone (0.5mg). These findings suggest that APO may be caused by a disturbance in the turnover of noradrenaline in the dentate nucleus and PPRF.
The expression of the five main groups of intermediate filaments and their subgroups, especially cytokeratins, was investigated in the guinea pig endolymphatic sac by light microscopy and immunohistochemistry. Immunoreaction for cytokeratin (PKK1, PKK2, PKK3) was found in the epithelial cell layer of the sac. Vimentin was seen to stain the epithelial cell layer as well as subepithelial tissue. These findings suggest that the cytokeratins are involved in the inner ear fluid transporting mechanism. The co-expression of cytokeratin and vimentin may be closely related to the dynamic properties of the endolymphatic sac which regulate inner ear fluid homeostasis.
Abnormal eye movements, characterized by only an upward reflex and slight inward rolling when gazing in any direction, were seen in an infant with idiopathic scoliosis. These abnormal eye movements were similar to these of Bell's phenomenon. Idiopathic scoliosis and Bell's phenomenon-like eye movements were presumed to be caused by immaturity of the brain-stem, and they improved slightly over 8 years as the brain-stem matured.
We examined 256 patients who suffered from vertigo with routine otoneurological techniques and got diagnosis from 1985 to 1987. CT-scans were often performed to confirm the diagnosis. Positional nystagmus was present in 72 patients (28.1%). The proportion of positional nystagmus was not very different among the various diseases. Direction changing nystagmus was seen in about 40% of patients with peripheral as well as central disease, although textbooks describe a higher incidence of direction-changing nystagmus with central lesions than with peripheral lesions. Among the patients with direction-changing nystagmus, upward nystagmus was seen in about 70% of those with peripheral disease and in about 80% of those with central lesions, although textbooks describe direction-changing upward nystagmus mainly in patients with central disease. Rotatory nystagmus indicated a peripheral lesion rather than a central lesion.
Vestibular neurectomy was performed on a 42 year-old man with left Meniere's disease. The patient had been suffering from persistent vertigo attacks with left tinnitus. Neurectomy was performed using Silver-stein's retrosigmoid approach. An ABR and a Silverstein's nerve stimulator monitor were used to monitor cochlear and facial nerve function during surgery. The vestibular nerve and the cochlear nerve were separated along the cleavage plane, and the vestibular nerve was cut preserving the cochlear nerve. Facial nerve function was complete after the surgery. The average hearing level was 61.7dB before the surgery, and 53.3dB after the surgery. No vertigo attack has been noted after the surgery, and the patient has returned to work. Vestibular neurectomy is considered to be a very effective treatment for persistent Meniere's disease.