The frontal eye field (FEF) is topographically organized in terms of sensory input from the environmental space as well as oculomotor output. Many visual neurons are located in the FEF. Those located in the lateral part of the FEF have the visual receptive field in the foveal region of the contralateral visual field, while those in the medial part have the visual receptive field in the eccentric region from the fovea. Many oculomotor neurons are also found in the FEF, the activation of which elicits saccadic eye movements of a particular amplitude and direction, depending on their location in the FEF: activation in the lateral part of the FEF induces a saccade with a small amplitude, while activation in the medial part induces a large saccade. The destination of the saccades is always in the contralateral visual hemifield. The visual and oculomotor neurons located at a given part of the FEF area related. A saccade elicited by activation of the oculomotor neurons is generally directed to the most responsive area in the receptive field of the visual neurons, suggesting that a transfer of neuronal activities from the sensory neurons to the motor neurons induces visually-guided eye movements. In addition, the FEF exhibits an inhibitory effect on oculomotor initiation and holds the image of the visual object to the foveal region. Activation of FEF neurons representing the foveal region suppresses saccade generation. Furthermore, this suppressive effect of the lateral part of the FEF functions even when a visual object is moving. Electrical activation of this area elicits slow eye movement resembling a smooth pursuit eye movement. Spike activities are also seen in neurons in this area during smooth pursuit eye movements. Based on these facilitatory and inhibitory functions, the FEF may contribute to the generation of normal orientation behavior, which is composed of selecting a particular object in the environmental space, visual fixation on the object for an appropriate duration, and shifting from the object to other objects in proper time.
An 84-year-old female with profound hearing loss in her left ear since her childhood, complained of vertigo attack with right fluctuating hearing loss and tinnitus. The clinical picture suggested a diagnosis “contralateral delayed endolymphatic hydrops”. On serological test, however, this patient showed moderately positive serology for syphilis. Precise re-inquiry indicated that she was infected with syphilis during pregnancy in her twenties. Thus, we treated this case with isosorbide dehydration, steroids and anti-syphilitic medication. As the result, vertigo attack was suppressed, hearing level became stable, and the rate of syphilitic serology was reduced. It is rare but noteworthy that this case of syphilitic labyrinthitis showed clinical course similar to delayed endolymphatic hydrops. In this paper, we would like to emphasize the necessity of excluding syphilitic labyrinthitis from the differential diagnosis of other vestibular diseases including delayed endolymphatic hydrops.
Introduction For transcranial magnetic stimulation of the facial nerve, a magnetic coil is fixed to the temporal region over the nerve. It has been reported that the facial nerve can be stimulated at the distal part of the auditory canal, and it is expected that the peripheral vestibular organs are included in the time-varying magnetic field. We examined the influence of magnetic stimulation on the peripheral vestibular organs using a stabilometer. Methods Experiments were carried out on 10 healthy adults. Magnetic stimulation was administered to the temporal region including the peripheral vestibular organs and stabilometry was performed before and after stimulation. We used a G5500 system stabilometer (Anima Co.) with a sampling time of 20 msec. and recorded body sway for 60 sec. A Mag lite (Dantec Co.) was used for magnetic stimulation and a Synax ER 1100 (NEC-Sanei Co.) was used as the trigger. The stimulus was set at 4 Hz and stimulation was done 60 times. The output was set at about 40% of 1.9 Tesla (maximum output). Results We analyzed the body sway length, 8-directional body sway velocities, and the power spectrum of the lateral body sway velocity. The total length of body sway and the velocity of lateral sway increased significantly after magnetic stimulation.
Prevalence of definite cases of Meniere's disease (M.D.) in Nishikubiki district, the western part of Niigata prefecture, was investigated. All of the hospitals and clinics were surveyed between Jan. 1 and Dec. 31, 1994. Definite cases of M.D. was defined by the criteria proposed by the Meniere's Disease Research Committee of Japan. There were 13 definite cases (12 cases reported from ENT clinics and 1 case from a general practice). Surveying all ENT clinics was quite useful for evaluating the prevalence of definite cases of M.D. in a restricted area. Prevalence was 23 per 100000.
A case of rotary nystagmus evoked by lateral eye position is reported. Rotary nystagmus is often observed in patients with BPPV (benign paroxysmal positional vertigo). In most cases of peripheral vestibular disorders, the rotary nystagmus is evoked by a change in head position, is diminished by the repetition of head position and has a latent onset time. The character of rotary nystagmus in this case differs from that caused by peripheral vestibular disorders. Nystagmus was observed in the right lateral eye position, was not associated with the change in head position and had no latent onset time. Although caloric nystagmus was well developed, caloric nystagmus with gazing increased on visual suppression test. In case of central disorders, a rotary nystagmus was reported. The medulla lesion, Wallenberg syndrome, syringobulbia, may cause a rotary nystagmus in frontal eye position. Sakata reported rotary nystagmus in the lateral eye position caused by a disorder in the nucleus of the trochlear nerve and cerebellum. Büttner reported rotary nystagmus in lateral gazing. He thought that confusion of equilibrium information caused by a cerebellar lesion and rotary nystagmus had developed. The skew deviation arose from a pons disorder. We thought that the imbalanced equilibrium was not strong enough to cause skew deviation, thereby causing rotary nystagmus in the lateral eye position. In this case, we can assume several hypotheses to explain mechanism for the nystagmus. The most likely explanation is functional disorder of the pons.
Hemorheological impairment is thought to be one of the pathological conditions of vertebro-basilar insufficiency (VBI). To determine the contribution of impaired red blood cell deformability (RCD), one of the important factors of hemorheological impairment, to the pathogenesis of VBI, RCD was measured and compared between a group of VBI patients (21 males, 42 females) and a group of control adults without vertigo (22 males, 23 females). Diagnosis of VBI was based on the Guidelines established by the Japan Society for Equilibrium Research. RCD was measured by the red blood cell (RBC) centrifugation method according to the criteria established by the International Committee for Standardization in Haematology. RCD was significantly decreased in the VBI group (p<0.01). Blood levels of total cholesterol and triglyceride in the VBI group were significantly higher than those in the control group (p<0.05). RCD was not correlated with RBC counts, Hb, Ht, MCV, MCHC, platelet count or total cholesterol or triglyceride level. Administration of dilazep dihydrochloride (300 mg/day for 8 weeks) to VBI patients induced significant (p<0.05) improvement in RCD and relieved vertiginous symptoms. Vertigo in VBI is considered to result from a combination of conditions involving microcirculation disorder induced by decreased RCD, decreased vertebral arterial blood flow due to high blood levels of total cholesterol and triglyceride, and rapid occurrence of right-left difference in blood flow by action stimulation.
The simple cold caloric test (20°C, 5 ml water irrigation for 10 sec. and stimulation for 20 sec.) is an established method of investigating right and left vestibular function separately. In addition, this test should decrease examination time and patient's discomfort. The caloric response in this test is considered to be normal when the maximal slow phase eye velocity (MSV) is not less than 20°/sec.. We have used the simple caloric test as one of the routine vestibular function tests. As stimulation, air irrigation (15°C, 61/min., 60 sec.) is used instead of water irrigation. We have experienced that the MSV in both ears equally showed less than 20°/sec., or a large difference although each ear revealed normal caloric response. Therefore, we reexamined the simple cold caloric test for 24 normal volunteers. The purpose of the study was to investigate in normal subjects whether the MSV of both ears was equal or a normal caloric response was obtained. The results were follows, 1) MSV not less than 20°/sec. was demonstrated in 83% of normal volunteers. 2) The MSV in these subjects ranged from 9°/sec. (minimum) to 50°/sec. (maximum). 3) There was good correlation between the right and left MSV (mean±2SD). It is concluded that, in the response to simple cold caloric test, there are individual differences but not very much difference between the right and left ear of the same individual.
We report a new algorithm that allows quantitative analysis of eye movements recorded with an infrared CCD camera, now widely used to examine nystagmus. With this camera, it is possible to observe minute eye movements and the recorded eye movements can also be replicated. We first divide a segment of a film of eye movements into frames and then subdivided the area of each frame into multiple blocks. A pattern-matching method is used to determine the direction and distance (i.e., vector) of the movement of the pixels in each block. The axis and angle of rotation of the eyeball are then calculated based on the derived vectors. Our algorithm has several advantages. It does not assume that the eyeball rotates around the center of the pupil, but calculates the axis of rotation. Accordingly, complicated eye movements can be analyzed, e.g., those in which the axis of cyclorotation does not cross the center of the pupil. It also minimizes the effects of noise caused by the eyelids, because multiple vectors are used to determine the eye movements. Therefore, it facilitates analysis of eye movements in patients with narrow palpebral fissures. It also eliminates the effects of infrared ray reflex on the bulbar conjunctiva.
The rotating sensation caused by optokinetic nystagmus (OKN) stimuli was studied. Twelve normal subjects were examined and subjects with tinnitus in the young group (20-39 years old), middle aged group (40-64 years old) and elderly group (65-years old) were examined. OKN was recorded by electronystagmography (ENG) and the maximum slow phase velocity (Max. SPV), optokinetic adaptation limit (OAL) were measured. The OKN drum velocity between the initiation of the drum rotation and the appearance of a rotating sensation or its disappearance were measured. The rotating sensation appeared earlier in the elderly group than in the young group. The rotating sensation seemed to appear earlier by repeated OKN examinations, while visual-vestibular response conduction time was shortened by repeated examinations.
Ocular Counterrolling (OCR) was induced using a body tilting apparatus, and change in OCR was recorded with the passage of time. In addition, changes in subjective cognition of direction and body axis associated with change in OCR were also analyzed. Based on the results, the time-course change in OCR was classified into two groups: Group I, showing constant change (response) and Group II, showing gradual reduction. In Group I, subjective cognition of gravitational axis and body axis was relatively accurate, while said cognition was less accurate in Group II. These results suggested that change in OCR is not simply induced by the otolith organ alone but affected by input from the trunk and deep sensation receptors; these factors may be involved in adaptation and habituation. This study also suggested that OCR reflects cognition of the body axis and direction or spatial orientation.
Introduction The vasovagal reflex causes spontaneous dizziness which appears in a standing or sitting position. This reaction is probably caused by the autonomic reflex. It has long been recognized that the plasma adrenaline (Adr.) level elevates during vasovagal attacks. However, the effect of Adr. on cerebral blood flow during vasovagal reflex has not yet been clarified. Purpose This study investigated the effect of Adr. on cerebral blood flow during vasovagal reflex in an experimental cat model. Methods Ten cats were tracheotomized and restrained in the supine position with its head raised at a 30-degree angle. Upon vagal neurotomy, the nerve fiber on the cardiac side was subjected to electrostimulation for 1 minute. Intravenous Adr. was infused at 0.25 μg/kg for 30 seconds. The regional blood flows in the nucleus vestibularis, nucleus olivaris inferior and nucleus fastigii were measured by the hydrogen clearance method. Changes in heart rate, blood pressure, and regional blood flow were compared among the three groups; Adr. injection alone (Adr. group), electrostimulation alone (electrostimulation group), and Adr. injection+electrostimulation (Adr.+electrostimulation group). Results Heart rate and blood pressure increased in the Adr. group (p<0.01), decreased significantly in the electrostimulation group (p<0.01), whereas there were no changes in the Adr. +electrostimulation group. Blood flows increased in the Adr. group (p<0.01), and decreased in electrostimulation and Adr.+electrostimulation groups (p<0.01). However, there was a more significant decrease in the Adr.+electrostimulation group than in the electrostimulation group (nucleus vestibularis: -3.5 vs. -3.9 ml/min/100 g, p<0.01, nucleus olivaris inferior: -9.4 vs. -2.5 ml/min/100 g, p<0.01, and nucleus fastigii: -7.8 vs. -2.8 ml/min/100 g, p<0.01). Conclusions Although Adr. increased cerebral blood flow, Adr. combined with vagal stimulation reduced blood flow more than vagal stimulation alone. This could be explained by accentuated antagonism.
Twelve normal adults, 50 patients with inner ear lesions and 33 patients with dizziness were examined by stabilometer to see how height affects spatial orientation especially on body balance. The subjects were requested to stand still on the stabilometer for 30 sec with eyes open and fixed on a target 2.1 m in front of the subject, and again with eyes closed in darkness. The total length and area of stabiolometry were measured while standing for 30 sec on the floor, and on a bed elevated 83 cm above the floor. 1. The total length and the area showed no significant difference between standing on the floor and standing on the bed in normal subjects. 2. In cases of inner ear lesions and of dizziness, there were significant differences in the total length of gravity movements between standing on the floor and on the bed, both with eyes open and with eyes closed. There were no significant differences in the area of the stabilometry. 3. There were no significant differences between patients with inner ear lesions and those with dizziness when they were standing on the floor or on the bed elevated 83 cm above the floor.