Sudden movements of a large-field pattern elicit ocular-following responses, which are short-latency tracking movements of the eyes. Ocular-following responses are assumed to help stabilize gaze on stationary objects. In our laboratory, we investigated the neural mechanism of ocular-following responses. Evidence from single-unit recordings has suggested that early ocular following is mediated by a pathway that includes the medial superior temporal (MST) area of the cortex, the dorsolateral pontine nucleus, and the ventral parafloccular lobes of the cerebellum. The results also suggest that the initial part of other slow tracking eye movements, the smooth pursuit and optokinetic response, share, at least in part, the pathway that mediates the ocular following.
Clinical and experimental reports have shown the functional role of the cerebellum in saccadic eye movement, and clinical tests in patients with cerebellar disorder have suggested that cerebellar function controlled the accuracy of saccadic eye movement in direction, amplitude and targetting. Therefore, participation of the cerebellum in eyemovement control was inferred from the effect of vermal and fastigial stimulation and from recordings of saccade-related activity form vermal lobules VI and VII (oculomotor vermis) and the fastigial nucleus (caudal part, fastigial oculomotor region, FOR). Saccades evoked by microstimulation of the oculomotor vermis resulted from the activation of purkinje cells and their axons and movement toward the ipsilateral direction was evoked. Saccades evoked by stimulations the dorsal part of the fastigial nucleus were also in the ipsilateral direction and were suppressed by bicuculline. These saccades were induced by stimulations the axons of purkinje cells arising from the oculomotor vermis. Saccades evoked from the ventral part were in the contralateral direction, and were induced by direct stimulation of fastigial neurons. Saccades were the result of activating purkinje cells, indicating that signals of stimulation are transmitted via the fastigial nucleus. These purkinje cells and fastigial neurons received the same mossy fiber inputs with relation to saccades. Neural recordings from the oculomotor vermis and FOR suggested that these areas controlled saccades in the direction contralateral to the amplitude and ipsilateral to the ending saccades.
Since 1975, the Research Committee on Ménière's Disease (MD) and Peripheral Vestibular Disorders in Japan has conducted several nation-wide and regional surveys according to the drafted criteria. The data collected were analyzed, and compared with control data obtained from other vertiginous, ENT patients and healthy subjects. The epidemiological characteristics obtained from these surveys were compared with that from surveys in foreign country, and were summarized as follows. 1) In MD, the male to female ratio has changed from even to a female prevalence over the past 15 years in Japan. 2) The distribution of age at onset peaked in the forties for males, and thirties for females in all nation-wide surveys. 3) In all nation-wide surveys, there was apparently a higher prevalence of MD among the so-called white-collar workers than among blue-collar workers. 4) The geographical distribution of MD was characterized by a preponderance in the southern area of Japan on the 1st and 2nd surveys. 5) The vertiginous attacks often occurred during regular working hours (9-17 h), and often resulted from mental and physical fatigue, and insomnia. 6) In MD, precise and neurosis were more frequently observed than in non-MD vertigo. 7) On meteorogical observations in Toyama, the onset of MD was specifically influenced by the passing of a cold front. 8) From nation-wide and regional surveys, the prevalence in Japan was estimated at about 16-38 per 100, 000. From these observations, it was reconfirmed that the occurrence of vertiginous attacks in MD is influenced much more by individual than by environmental factors.
Meniere's disease was diagnosed in 182 cases or 5.8% of 3, 150 patients who had consulted the Neuro-otological clinic in Kitasato University Hospital between 1990 and 1995. Females were dominant comprising 70% of 151 patients. Patient age at the onset of the disease ranged from the third to fifth decade. Patients were treated by medication and Portmann's sac procedure was done in 12 cases. Initial symptoms and prognosis of vertigo and hearing impairments were investigated in 28 selected patients who were successfully followed over a long term. Tinnitus and/or deafness started before the first vertigo attack in 61% of the 28 patients. The left ear was more frequently affected than the right and both ears were affected in 12.7%. The interval between the first and second attacks of vertigo was more than one year in 21.4%. More than one year passed since the last vertigo attack in 60.7%. However, an interval of more than one year during the long term course was also observed in the same percentage. Average of hearing levels did not change or had worsened at the end of long term follow-up in all 28 cases.
Optokinetic nystagmus (OKN) of elderly Japanese was investigated as voluntary OKN and reflexive OKN, and results were analyzed both quantitatively and qualitatively. Subjects were healthy elderly Japanese over 65 years-old, and the OKN of these subjects were compared with those of healthy individuals in their 20's. Experiments were conducted by Ohm-type rotating cylinder at 2°/sec2 for 90 seconds. Data were analyzed by a microcomputer. In the qualitative test, voluntary OKN was assessed as follows: delay of pursuit movements, deficit of smooth pursuit, delayed initiation in target catching and defect of catching movements; and reflexive OKN was assessed by the quality of nystagmus waves and nystagmus stripes. In the quantitative test, both voluntary and reflexive OKN were assessed by the number of nystagmus beats, slow phase velocity and rapid phase velocity. The qualitative analysis of voluntary OKN showed a deficit of smooth pursuit, such as, saccadic pursuit, in many cases. Quantitatively, when the cylinder speed exceeded 40°-60°/sec, the slow phase velocity decreased in many cases. Furthermore, the rapid phase velocity decreased in some cases, and when compared with the rapid phase velocity per amplitude of younger subjects (in their 20's), that of elderly subjects was significantly lower. The results of the qualitative and quantitative tests of reflexive OKN showed a few abnormalities.
In 1974, the Meniere's Disease Research Committee of Japan published recom-mended guidelines for diagnosis of Meniere's disease. This guidelines advocated definite Meniere's disease (DMD) and probable Meniere's disease (PMD). DMD was defined as repeated rotatory vertigo, fluctuating cochlear symptoms and exclusion of other causes. PMD was defined as repeated rotatory vertigo and exclusion of other causes or fluctuating cochlear symptoms and exclusion of other causes. We divided PMD patients into four groups as follows: Group I: Three or more definite episodes of rotatory vertigo and non-fluctuating cochlear symptoms. Group II: Three or more definite episodes of rotatory vertigo without cochlear symptoms (vestibular MD). Group III: One or two definite episodes of rotatory vertigo with fluctuating cochlear symptoms. Group IV: Fluctuating cochlear symptoms without vertigo (cochlear MD). The time course of fluctuating hearing loss in groups III and IV was similar to that in DMD. The time course of patients who showed canal paresis or directional preponderance on bithermal caloric irrigations in DMD was similar to those in Groups III and IV but different from those in Groups I and II. We speculated that PMD could be divided into four morbid states as follows: 1. Progress to DMD in the future. 2. Similar to old DMD. 3. Similar to remission of DMD. 4. Different disease from DMD. Some PMD patients might be able to control vertigo and/or cochlear symptoms by therapy, while in other patients repeated vertigo and/or fluctuating cochlear symptoms might not appear during the natural course. It is important that the patients with PMD be treated as carefully as those with DMD.
Whether basophilic deposits adhered to the cupula and canal wall in the endolymph in each semicircular canal was histologically investigated in this study. Results indicated that basophilic deposits were present in all three cupulas and the walls of the semicircular canals. The overall incidence of basophilic deposits in the cupula or wall of the superior, lateral and posterior semicircular canal was 32%, 44% and 47% respectively. The incidence of basophilic deposits bound to the cupula and wall increased with age. The possible origin of these basophilic deposits on the cupula and walls, the increased incidence of basophilic deposits with increasing age, and the kinds of positional nystagmus caused by such basophilic deposits are discussed. In conclusion, it was suspected that the origin of these basophilic deposits was otoconia detached from the otolithic membrane in the utriculus. This finding that otoconia became detached from the membrane involved the temporal bone pathological lesions with aging and direction-changing positional nystagmus to the upper or lower ear side were caused by the cupulolithiasis and canalolithisis respectively.
Diagnosis and age at on set were investigated in 18, 246 vertiginous patients who had visited the neuro-otological clinic in Kitasato University Hospital between August 1971 and December 1995. There was a high incidence of the patients in the 4th decade, but the age distribution showed a recent tendency to shift toward older patients. The proportion of patients with peripheral vestibular disorders, diseases of the central nervous system, generalized diseases and others were 30.1%, 17.7%, 6.6% and 45.6%, respectively. Ménière's disease was diagnosed in 6.67% and BPPV in 4.72% of all patients.
Platelet aggregation in 185 patients with vertigo and dizziness (174 mild and 11 serious cases) were studied between November 1989 and April 1996, also 63 healthy subjects and 20 cases of vascular occlusive diseases in the post-acute phase (12 patients with ischemic heart disease and 8 with cerebral infarction) were studied as control groups. This study evaluated the maximum aggregability (aggregability) induced by 2 μg/ml COLLAGEN and 2 μM ADP. The results are as follows. 1. Aggregability of patient sera was significantly higher than that of healthy subjects. However, there was no significant difference between groups with peripheral, central and other disorders. 2. Factors affecting aggregability were stress in patients with peripheral disorders and cholesterol in those of central disorders. 3. The mean value of aggregability of 185 patients was between the value in healthy subjects and that in patients with vascular disorders. 4. Aggregability at a high level persisted for a long period even when the patient became asymptomatic. And during the recovery, when stress or hyperlipidemia was persistent, aggregability could increase. Therefore, even after symptoms disappear, risk factors such as stress or hyperlipidemia should be avoided.