Electrical stimulation of the caudal zone of the cat's cerebellar flocculus evoked a downward smooth eye movement. Electrolytic injury of the vestibular group y nucleus abolished this smooth eye movement. There may be a pathway from the caudal zone to the extraocular motor nucleus via group y nucleus related to vertical smooth eye movements. This pathway may contribute to the vertical optokinetic system in driving a vertical slow phase and/or smooth pursuit eye velocity. It also apperared that the cerebellar flocculus contributes to the optokinetic system in driving a horizontal slow phase and/or smooth pursuit eye velocity.
The cat's cerebellar flocculus can be anatomically divided into three microzones on the basis of differences of their efferent projection sites. We investigated the eye moverents evoked by electric stimulation of each microzone of the flocculus in ketamine-anesthetized cats. An upward eye movement was evoked by stimu-lation of the rostral zone, an ipsilateral horizontal eye movement by stimulation of the middle zone, and a downward eye movement by stimulation of the caudal zone. Stimulation of the flocculus might activate Purkinje cells which inhibit the vestibular nucleus neurons and might cause eye movement. An upward eye movement was evoked by electric microstimulation of group y of the vestibular nuclei. Destruction of group y eliminated the downward eye movement evoked by stimulation of the caudal zone of the flocculus. Purkinje cells in the caudal zone might inhibit group y neurons and might contribute to vertical eye movements in cats.
Cytological studies were carried out in serial sections of the human vestibular ganglion obtained at postmortem examination. They were fixed with 2% osmic acid (pH 7.4) and LEVI's solution and stained with AZAN. The human vestibular ganglion was found as nodules among the vestibular myelinated fibers. In the vestibular ganglion the ganglion cells were seen among the loose collagen fibers and nerve fibers, separated from one another. These ganglion cells were bipolar and spindle shaped, varied somewhat in size and were mostly surroqnded by their myelin sheaths. Myelin sheaths of myelinated nerve fibers in the ganglion were usually thicker than the perikaryal myelin sheaths. In the ganglion there a few unmyelinated cells, which may belong to the autonomic nervous system. We are convinced that the human vestibular ganglion cells consist mostly of bipolar myelinated cells as in other mammals, such as the rabbit, bat, etc..
Corneo-retinal potentials of normal subjects were investigated before and after optokinetic stimulation, eye tracking and caloric stimulation. After the optokinetic pattern test, where the maximum angular velocity of the stimulation was 150°/ sec, the corneoretinal potential increased significantly. This potential also increased after relatively high speed optokinetic stimulation with a constant angular velosity of 45°and 60°/sec. However, the potential remained unchanged after low speed optokinetic stimulation of 15°and 30°/sec. The eye tracking test and caloric stimulation also produced no change of corneoretinal potentials. It is speculated that the increase of the corneoretinal potentials after the optokinetic pattern test is caused by the rise in activity of the retinal cells, since high speed optokinetic stimulation affects retinal vision mainly, whereas in low speed optokinetic stimulation or eye tracking affect the foveal vision mainly.
Frequency-components of body sway while standing upright usually show some minor changes in normal individuals. The human standing posture depends on righting reflexes controlled by the multi-channel sensori-neuro-muscular system and several other factors, such as biorhythms of the body, the mental state, etc. However, we simply accept fluctuation of the data without considering the characteristic frequency patterns of body sway in both normal and ataxic patients. The reproduce ability and steadiness of the data of frequency analysis of the movement of the center of gravity were investigated repeatedly in three normal subjects standing erect on different occasions. The results were compared with the one-time data from 20 normal subjects. The three subjects stood for one minute with eyes open and for one minute with eyes closed nine to 11 times every one or two weeks. The same subjects stood for ten minutes with eyes closed and ten data of every one minute in each case were also investigated. The percentages of the sums of the amplitude in seven frequency ranges, decided arbitrarily, to the total amplitude under 10 Hz were calculated. It was found that the degree of fluctuation in the frequency pattern of body sway during repetitive standing, either continuously of at long intervals, remains within the limit of fluctuation observed in 20 normal subjects.
The conditions required for a new rotation test were defined as (1) to obtain findings not detectable by other tests, especially caloric tests, (2) to reflect the most important function of the vestibulo-ocular reflex and (3) to have specificity and sensitivity as a clinical test. The active head rotation test is a new test in which the vestibulo-ocular reflex and smooth pursuit can be demonstrated by measuring the abilities of spatial fixation and fixation suppression during daily experienced fast head rotations in the light. The findings and clinical application of this test are described.
The amplitude of the vertical saccades of 25 normal adults was studied by electronystagmography or by a computerized eye movement analysis system. A round target 1 cm in diameter moved with a visual angle of 10° or 20° or 30° and with circular movements or with vertical sinusoidal movements or with vertical saccades. 1. The amplitude of the vertical saccades increased as the visual angle widened from 10°to 30° when the target movements were circular. The amplitude of the verical saccades with vertical sinusoidal target movements or vertical saccadic movements decreased as the visual angle increased to 20°or 30°. 2. The amplitude of vertical eye movements varied most when saccadic target movements were used and was steadiest when the target moved vertically sinusoidally or circularly clockwise. 3. Vertical eye movements movements should be calibrated with a visual angle of 20°or 30°and circular target movements.
There is often difficulty in the clinical diagnosis of disorders of the vascular territory of the anterior inferior cerebellar artery (AICA) which frequently associated with inner ear and brain stem disorders. Three cases of AICA disease are reported and the characteristics of these disorders are discussed. 1) Many anatomical variations have been detected in the AICA. Therefore, no typical AICA syndrome can be demonstrated in many instances. 2) A large number of patients with vascular disorders of the AICA, especially those with infarction do not have signs or symptoms of cerebellar dysfunction. 3) The AICA is a vital artery of the inner ear. Therefore, the disorders of the AICA are often related to inner ear disease. 4) It is unusual that we get obvious findings of vascular disorders in VAG examinations and CT scan examinations show many artifacts in territory of the AICA. Therefore, niether examination is very useful in the diagnosis of such disorders.
Unusual and bizarre abnormalities of ocular movement are often valuable localizing signs in central nervous system diseases. Square wave jerks (SWJ) are sporadic horizontal conjugate saccades away from the intended position of fixation, followed some 200 msec later by saccadic return to the fixation. SWJ are recognized as a normal phenomenon when present only under closed eyelids. SWJ during fixation are considered to be a pathological sign, indicative of cerebellar disease. Reports of SWJ in progressive supranuclear palsy, multiple sclerosis, posttraumatic cerebral syndrome, presenile dementia, and cerebral tumors suggest that brain stem or cerebral hemispheric disease may also be responsible. The mechanism of SWJ, however, remains unceretain. The present paper reports six cases of SWJ in two patients with cerebellar infarction, one with cerebellar hemorrhage, two with spinocerebellar degeneration, and one with dentato-pallidal degeneration. The localizing value of SWJ and its mechanism of action are discussed. SWJ were conjugate, horizontal, symmetrical, occurred in burtst of several seconds, had amplitudes of 4° to 35°, and were evoked whenever the patient attempted to shift visual fixation or pursue a moving target. Electronystagmographic recordings in one patient with cerebellar hemorrhage showed the following features of this disorder of saccadic eye movement : 1) SWJ was composed of saccades, 2) their frequency was 0.5 to 2 Hz, 3) bursts occurred with decreasing amplitude and 4) the eye position did not exhibit systematic drift during the intersaccadic period. These features reflect the increased gain and instability of the visually guided saccadic system. Our resuls suggest that the loss of the calibrator function of the cerebellum accounts for the development of the abnormality underlying SWJ, and that SWJ are the result of unwanted supranuclear trigger signals that interrupt the saccadic pulse-step control system thereby releasing saccadic burst units.
Previously we reported the method and clinical findings of the Galvanic Body Sway Test (GBST). GBST was very useful in the differential diagnosis of diseases of the labyrinth and central vestibular disorders, but it did not provide clear answers when the body sway was very large. In order to record clear responses, we developed a new method of stimulation in the GBST. The polarity of the stimulating current applied to one ear was reversed from positive to negative in stimulation. Very large body sway to the left and right was elicited by reversing stimulating polarity, and galvanic responses became clearer. This effect was most remarkable in cases of very large body sway.
In an attempt to evaluate equilibrium disorders of patients with scoliosis, we performed equilibrium fumction tests : spontaneous gaze, positional, neck torsion, and neck compression nystagums ; and Romberg's Mann's and stepping tests. 1) Some kind of equilibrium disorder was observed in 90 out of 117 patients. (76.9%) 2) Spontaneous or positional nystagmus was observed in 34 out of 117 patiints. (29.1%) 3) Spontaneous or positional nystagumus was frequent during childhood. 4) No correlation was noted the location of the scoliosis and the incidence of spontaneous or positional nystagums. 5) Spontaneous or positional nystagmus increased with the incicidence of scoliosis, but not significantly. 6) Unexpected, when the asymmetry of the spine increased, the incidence of spontaneous or positional nystagmus decreased.
In this investigation of the interaction between the visual and vestibular systems in patients with focal lesions of the central nervous system, the visual vestibulo-ocular reflex (VVOR) gain and the vestibulo-ocular reflex (VOR) gain in 13 normal subjects and 64 patients with central nervous system disorders were analyzed by a mini-computer (PDP 11/34) with harmonic sinusoidal rotation and optokinetic stationary stimuli. The test subjects were rotated sinusoidally at an amplitude of 120° and at a frequency of 0.1Hz (maximum velocity 75.4°/s), with eyes both closed and open. In 64 patients with central nervous system disorders, many types of abnormal VOR and VVOR gains were observed. Decreased VOR and VVOR gains were frequently seen in patients with brainstem lesions. Our results of VOR and VVOR tests indicated that: 1) these tests are useful not only as screening tests but also for the topodiagnostic evaluation of central nervous system lesions; 2)they are useful and appropriate system for following the progress of the disease ; 3)some patients with central nervous system lesions showed a change, either a decrease or an increase of VOR.
Of the 464 patients with suspected intracranial lesions who had equilibrium function tests at the University of Occupational and Environmental Health 56 recived CT-scans. Twelve (21.4%) had an abnormal CT-scan. The most frequent pathological finding was cerebral atrophy, followed by acoustic tumor and cerebral infarct. Of the equilibrim function tests, the optokinetic pattern test (OKP), the pendular rotation test (PRT), the visual suppression test and Romberg's test were significantly abnomal in patients with abnormal CT-scans than in those with normal CT-scans. Six patients had abnormal results in the OKP, PRT and visual suppression tests ; five of these had profound hypofunction of the labyrinth by caloric testing. Therefore, in patients with abnormal OKP, PRT and visual sppression tests and profound labyrinthine hypofunction in caloric test CT-scan is indicated.
We have often seen patients with so-called "tong-enital nystagmus", almost all of them with horizontal nystagmus. Forsythe, Biard and several other authors have described cases of congenital vertical nystagmus, but their diagnostic criteria were not clearly defined. As far as we know congenital vertical nystagmus with inversion of the vertical optokinetic reaction has never been reported. (It has been demonstrated that optokinetic inversion is essential for diagnosing congenital horizontal nystagmus. Also this inversion could be adapted for congenital vertical nystagmus.) We have recently examined a patient with congenital vertical nystagmus with inversion of the vertical optokinetic reaction. There were : 1) high frequency nystagmus inhibited by covering or closing the eyes, 2) no oscillopsia, 3) a positive family history, and 4) inversion of the vertical optokinetic reaction
A 55-year old male patient complained of tinnitus of the left ear, dizziness (oscillopsia) and left hemifacial spasm. Neurotological examination revealed clockwise horizontal-rotatory nystagmus. The nystagmus changed to counter-clockwise horizontal-rotatory during episodes of left tinnitus. Left hemifacial spasm around the eye and cheek was frequent. Vertebral angiograms revealed an abnormal loop formation of the posterior inferior crebellar artery. These findings suggested that the symptoms were due to compression of the facial nerve and acoustic nerve by vascular structures. Microsurgery confirmed our diagnosis, and the patient was symptom-free after vascular decompression. The uses of neurotological examinations are discussed.
The present state of the patients vistiting various types of clinics with complaints of vertigo and/or loss of balance was analysed by questionaires sent to otolaryngologists in private practice, to those in large general hospitals and University medical ceters and to a certain group of neurologists in Japan. According to 246 replies to 530 questionaires, equilibrium function tests such as the test of spontaneous nystagmus, deviation test, tests of righting function and Schellong's test were done routinely in most cases, and patients who complained of vertigo and/or loss of balance were treated vigorously by most doctors. However, a difference in attitude was noted between otolaryngologists in private practice in Hyogo prefecture and the other groups of otolaryngologists, the former being less apt to treat vertigo patients agressively,
Questionnaires enquiring about the number of patients with vertigo and/or disequilibrium seen in various clinics and the frequency of vestibular examinations were sent to 50 neurosurgeons, 36 neurologist, and 38 internists specilalizing in cardio-vascular disease. The percentage of patients with vertigo and/or disequilibrium seen on a certain day was 10.0% in neurosurgery, 12.5% in neurology, and 5.8% in internal medicine clinics. Some vestibular examinations (standing test, gait exam, writing test, and observation of spontaneous nystagmus and voluntary eye movements) were performed quite often in neurosurgery, neurology, and otolaryngology clinics. However, other examinations such as positional and positioning nystagmus tests, electronystagmography, caloric test, optokinetic nystagmus test, eye tracking test, observation of body sway, and rotation test were less frequently performed in neurosurgery and neurology than in otolaryngology clinics. All these examinations were performed less frequently in internal medicine clinics.