Alcohol affects the oculomotor system and postural reflex, and vestibular nuclei are thought to be involved in both. In the medial vestibular nucleus (MVN), alcohol potentiates the effect of T-aminobutylic acid (GABA). Spontaneously firing MVN neurons were examined for alcohol in a brain stem slice. GABA suppressed the spikes evoked by local stimulation in the MVN neuron at the IC50 of 2 mM. One-percent alcohol potentiated the inhibitory effect of GABA, and the IC50 decreased to about 0.3 mM. Acutely dissociated MVN neurons showed similar spontaneous activity. Alcohol (0.01%) also potentiated the inhibitory effect of GABA in this preparation. The vestibular nuclei were particularly sensitive to alcohol in the brain. Therefore, the effect of alcohol is thought to be based on the potentiation of the action of GABA.
The cerebral cortex is considered to be the most important part of the brain, since it plays an essential role in highly complicated functions such as cognition, feeling, thinking, attention, consciousness, memory and learning. The basic design or architecture of the intracortical neural circuitry is, however, not understood enough to explain these functions, and needs to be investigated extensively. Here, I introduce our efforts to reveal the local connectivity of the cerebral cortex using the 'from one to many' strategy. By combining intracellular staining (from one) and Golgi-stain-like labeling of functionally grouped neurons (to many), we are trying to visualize the neuron-to-neuron connections in the cerebral cortex.
Intense clicks evoke short-latency myogenic potentials on the sternocleidomastoid (SCM) muscle ipsilaterally. These potentials are named"vestibular evoked myogenic potentials (VEMP)" because they are lost after vestibular deafferentation, but independent of the cochlear function. To induce VEMP, the subjects need to contract their SCM muscle during the test. The characteristics of the tuning curve of VEMP are a high threshold and low best frequency. They are similar in animal studies, suggesting that the saccule is the most promising candidate for the origin. Some diagnostic merit has been reported in previous papers. First, there is a discrepancy between VEMP and caloric response in patients with both inner ear and retrolabyrinthine disorders. Therefore, the test battery of these two tests is very useful for diagnosing vertiginous patients. Second, the Tullio phenomenon, the phenomenon of vertigo or loss of balance due to intense sound, is also evaluated by using VEMP. The Tullio phenomenon has been found in patients with various disorders, including congenital syphilis, Meniere's disease and perilymphatic fistula. VEMP are expected to be used in a new vestibular function test to evaluate the neural pathway from the saccule to the SCM muscle.
The medical service staff always have to be aware of recognizing the differences between physicians and patients. In this study, we clarified some problems of patients with vertigo via a questionnaire and consultation through the internet, and also investigated the limitation and problems concerning internet communication. The contents of the e-mail consultations included the symptoms of disease, diagnosis of disease, physicians in-charge, and prescriptions, in this order. The advantages of communicating through the internet are its ease of use, anonymity for patients with vertigo, answering e-mails can be available at convenient times, and e-mail documents are easy to save. However, the disadvantages are that only general and basic information is given, and there is still no conclusive agreement on medical counseling through the internet.
Direction changing positional nystagmus (geotropic and apogeotropic) used to be considered to indicate the presence of central nervous system lesions, especially in the flocculonodular lobe of the cerebellum and the brainstem. Recently, however, several reports have suggested that such positional nystagmus is more likely to be caused by a peripheral vestibular lesion. Particularly, benign paroxysmal positional vertigo, which may originate from the horizontal semicircular canal (HC-BPPV), was first reported by McClure in 1985. The present study reports 23 patients with positional vertigo who were diagnosed as having HC-BPPV in terms of the clinical and roentgenographic findings. Eight patients in the present series showed direction changing apogeotropic positional nystagmus, whereas the remaining 15 had direction changing geotropic positional nystagmus. In most patients, a short latency (less than 5 seconds) was observed between head positioning and the onset of nystagmus, but it tended to be shorter in the former group of patients. In addition, whereas the nystagmus in patients in the former group persisted for more than 1 minute and showed no fatigability with repeated positioning, the nystagmus in the latter group of patients was only transitory and exhibited fatigability. There has been no established physical therapy for positional vertigo with position changing apogeotropic nystagmus. The present study showed that Brandt-Daroff exercise considerably reduced the time to remission, which took an average of 41.3 days in patients with no treatment, and occurred within an average of 12.8 days in those who underwent the physical therapy. The present study also confirmed the effectiveness of Lempert's maneuver for the patients with geotropic nystagmus. This maneuver reduced the time until remission from an average of 11.0 days to 1.9 days.
It is difficult to determine the actual period of time that the vestibular nerve is activated after applying a caloric stimulus. Several processes are activated by the caloric stimulus, including convection currents in the canals as well as direct heating or cooling of the vestibular nerves. In turn, the neural activity excites both direct and indirect (velocity storage) vestibulo-ocular pathways, all of which contribute to produce nystagmus. Velocity storage has integrative properties that can be altered by the presence of stationary visual surroundings, which discharge stored activity and shorten the velocity storage time constant. Therefore, eye velocity generated by velocity storage can be used as a test to determine whether there is still activity in the nerve. To eliminate convection currents in the semicircular canals, we used an all-six-canal-plugged cynomolgus monkey. Eye movements were recorded using a dual-search coil system. Eye velocity was expressed as a vector comprising horizontal, vertical and torsional components. Caloric nystagmus was induced by irrigating the eardrum in light in the upright position with 10 ml water at 20°C irrigation for 15 sec. The animal was left in light for periods of time ranging from 10-110 s. At the conclusion of the period in light, the animal was put in darkness and caloric nystagmus, if any, was analyzed. If there was nerve activity, it would charge the velocity storage and nystagmus would return. For periods of light dump up to 110 s, caloric nystagmus ended 130 s from the start of irrigation. For periods of light dump more than 110 s, no caloric nystagmus appeared when the animal went back into darkness. The time of culmination, i.e., the time to reach the peak value of caloric vector, was 26 s in light, and the peak magnitude of the caloric vector was 86°/s. In darkness, the culmination was 11 sec from the point where the lights were extinguished. The magnitude of the caloric vector was 256°/s initially when there was no light dump, and it decayed exponentially according to the period of preceding visual suppression. The time constant of caloric nystagmus also decayed exponentially depending on the period of the preceding light dump. These results suggest that the duration of the effective thermal change for inducing caloric nystagmus was 110 seconds, and velocity storage contributes an additional 20 s (15%) to the duration of the first phase.
The gravic body sway test has been widely used as a body equilibrium test. The locus length, area and other parameters of gravic body sway correspond sufficiently to quantitative evaluation. However, quantitative evaluation is difficult for statokinesigraphy, which is the basis of gravic body sway evaluation. The author searched for a quantitative method to classify this. Consequently, in 1983, three patterns were shown by Wilks' Λ analysis, which is a statistical method, and the graph drawn for the classification was shown as a body sway pattern curve (BSPC). However, it was unknown what pattern of gravic body sway the BSPC consisted of. Thus, by using a simulation model, the author investigated what pattern of gravic body sway locus makes the BSPC shown by the Wilks' Λ analysis method and what gravic body sway locus actually means. As a result, the following facts were found when the property of the simulation was examined by Wilks' Λ analysis. In the locus of the equal speed, the BSPC is not related to the extent and size. The BSPC changes according to the frequency (speed) of the movement. This means that the interpositional relation of the movement over time changes the BSPC. When the position changes greatly over time and never approaches closely to the original position, the BSPC shows a sharp decline. Such body sway is shown, especially when the movement is multicenter type or similar to it, to have multiple body sway planes for the center of gravity. From these findings, it was found that since the BSPC indicates the interpositional change of the movement over time, features of the movement to control the posture are shown.
We had reported that patients with idiopathic unilateral auditory and/or vestibular symptoms who had ipsilateral displacement of the basilar artery (BA) at a significantly high incidence were evaluated with axial view T2-weighted MR images (MRI). In this study, the distance of BA displacement from the midline was measured in 25 patients with idiopathic unilateral auditory and/or vestibular symptoms (15 females and 10 males; mean age, 63.0 years). MRI of 17 patients with sudden deafness or vestibular neuronitis (9 females and 8 males; mean age, 53.9 years) were used as controls. The mean distance of 5.5 mm in the 25 patients was significantly further than that of 2.9 mm in the controls. This result highly suggests that idiopathic unilateral auditory and/ or vestibular lesions developed as a result of sclerotic change of the vertebrobasilar artery.
Head movements while walking were analyzed with a 3-D motion analyzing system (Mac Reflex) composed of 2 infrared digital CCD cameras and a data processor. Analysis focused on head translation along the vertical axis and rotation in the sagittal, coronal, and axial planes. Thirteen normal and 2 unilateral vestibular defective (VD) subjects performed 5 walks with their eyes open (EO) and 5 walks with a blindfold (EC). Additionally, normal subjects were tested after caloric stimulation with EC. In normal subjects, head translation and rotation in the sagittal and coronal planes were found to be significantly smaller during walking both with EC and after caloric stimulation with EC than during walking with EO. In VD subjects, these parameters also showed a tendency to decrease in the EC condition. Daily behaviors such as gazing, walking and running are controlled depending on spatial orientation, which is reconstructed in the brain by integrating information from multiple sensory organs. This study suggests that impairment of the sensory system (e.g. visual suppression or vestibular deficit) changes spatial orientation in the brain and causes a change of locomotor patterns, improving sensitivity of other sensory systems (e.g., otolithic or somatosensory input).
This study indicates that head position during sleep is likely to contribute to the pathogenesis of benign paroxysmal positional vertigo (BPPV). Seventy-two patients, consisting of 54 with posterior semicircular canal BPPV and 18 with lateral semicircular canal BPPV, were examined (BPPV group). Seventy-six healthy individuals of statistically the same age and sex as those of the BPPV group were also examined (healthy group). This study revealed that the percentage of people who always sleep in the same head position, particularly with the right side or left side down, amounted to 61 % of the BPPV group and 24% of the healthy group, which was significantly different (p<0.005). In 39 BPPV patients, (mean follow-up of 7.7 years) the recurrence rate was 41%, and the persistence rate was 13%. When patients were consulted to avoid having a fixed head position during sleep, the recurrence rate decreased to 18%, and the persistence rate decreased to 3%. In addition, almost all recurrent patients were ones who could not avoid a fixed head position during sleep. There was no correlation between the affected side of BPPV and the particular head position during sleep. In patients with latent inner ear disorders and/or utricular damage of unknown origin, habitually sleeping with the head position down on the right side or left side might induce otoconial detachment, causing BPPV and recurrence or persistence of BPPV. As an important possible cause of BPPV, the head position during sleep should be taken into consideration.