Stroke is the most important and frequent cause of central vertigo and dizziness. The diagnosis of stroke-derived vertigo/dizziness has improved due to the remarkable advance of imaging technology including MRI. The affected lesion is usually located in the vertebrobasilar artery territory. Additional symptoms such as diplopia, dysarthria and limb ataxia may contribute the precise diagnosis. However, the fact that about 10% of patients with isolated vertigo/dizziness show stroke lesions on MRI and/or CT must be taken into consideration.
To evaluate the influence of somatosensory input on the vestibulo-ocular reflex (VOR), we assessed 19 young, healthy volunteers with sinusoidal rotation tests. For the control condition, subjects, with their eyes open, were sinusoidally rotated in complete darkness at a frequency of 0.2 Hz with a maximum angular velocity of 30°/s for 30 seconds, and at frequencies of 0.4 and 0.8 Hz with a maximum angular velocity of 60°/s for 30 seconds. Sinusoidal tests were performed at earth vertical axis rotation (EVAR) and 30°nose-up, off-vertical axis rotation (OVAR). In addition to these controls, we implemented two different somatosensory stimulation conditions during the rotation tests as follows. (1) Subjects were told to grasp an earth-fixed metallic bar with their right hand. Thus, their right arm continued to move as the rotating chair apparatus moved. (2) Subjects put a vibrating belt around their waists, so that they felt vibrations on their trunk. We observed a significant increment (34%) in VOR gain change only at 0.2 Hz EVAR when subjects held the bar compared to that of the controls, who did not hold the bar. Gain change did not differ significantly across the other conditions, including OVAR or vibration stimulation. We propose that arthrokinetic input (i.e., arm movement) had an additive effect on VOR in this study. This input might relate to a low-frequency component that strongly enhances the velocity storage system. Our findings have applications to types of vestibular rehabilitation regimens that implement somatosensory input. Space motion sickness remains a troublesome, serious problem for astronauts traveling in space. This condition frequently occurs shortly after attainment of and sustained exposure to microgravity and affects 73% of crewmembers on the first 2 or 3 days of their initial flight. We hypothesized that somatosensory input supports may reduce dizziness or space motion sickness.
This study was conducted to investigate the characteristics of the functional reach test (FRT) in persons with intellectual disabilities (ID). The subjects were 41 persons with ID (male, 26; female, 15) and 44 healthy persons (controls). The subjects with ID were classified into two groups according to their intelligence quotient (IQ): the high-IQ and low-IQ groups. FRT was measured in the original (no target) condition and target condition. In the target condition, a white wall (target) was set in front of the subject. The FRT scores of the original condition and target condition and the difference between these FRT scores (FRT difference) were calculated. In the original condition, the FRT score of the controls was higher than those of the two groups with ID, in which no further comparison was significant. In the target condition, the FRT score of the controls was higher than those of the two groups with ID; the score of the high-IQ group was higher than that of the low-IQ group. The FRT difference of the high-IQ group was higher than that of the low-IQ group, which in turn was higher than that of the controls. These results suggested that persons with ID demonstrate a lower FRT score than healthy persons although the score can be increased greatly by the target, especially for persons with mild or moderate ID.
We report on 2 cases where edaravone (radicut®) was effective against acute brainstem and cerebellar infarction with vertigo. Patient 1 was a 74-year-old woman who had hypertension and presented with sudden vertigo. When she was admitted to our hospital, she had dysarthria and left hemiplegia. MRI performed on the first day and 3 days later did not show any abnormal regions. MRI performed 10 days later showed an abnormal region in the right ventrolateral medulla oblongata. Edaravone treatment was effective for her brainstem infarction. Patient 2 was a 50-year-old man who experienced sudden attacks of vertigo. Gaze nystagmus towards the left was noted. Head CT yielded normal results. Pure-tone audiometry showed profound right-sided sensorineural hearing loss. Initially, we considered that the patient had sudden deafness with vertigo, but he developed dysarthria after admission. Therefore, MRI was performed and showed a cerebellar infarction in the territory of the anterior inferior cerebellar artery. The patient was finally diagnosed as having anterior inferior cerebellar artery (AICA) syndrome. Therapy with edaravone, a free radical scavenger, was effective not only against cerebellar infarction but also against sudden hearing loss. MRI is essential for final confirmation of the diagnosis in such cases. However, sometimes, it does not show any definite abnormalities in the case of hyperacute brainstem and cerebellar infarction. We therefore consider neuro-otological examinations - in particular nystagmus assessment - as very valuable tools for clinical diagnosis in such cases.
There is little definitive evidence of the clinical significance of the vestibular-cardiovascular reflex in humans, despite the fact that the vestibular system is known to contribute to cardiovascular control in animals. Our first finding in this paper was that about 10% of 1479 dizzy patients in our hospital met the criteria for orthostatic hypotension (OH) set by the American Autonomic Society (2011). Second, a positive rate of the criteria for the OH was significantly higher in patients with abnormal subjective visual vertical (SVV) than patients with normal SVV, however abnormality of canal function did not affect the positive rate of the OH. Third, we classified 248 dizzy patients aged<65 into three groups based on their vestibular evoked myogenic potential (VEMP) responses; absent VEMP, asymmetry VEMP and normal VEMP. In order to investigate the effect of the otolith disorder, which was estimated by the VEMP, on the orthostatic blood pressure responses, the subjects' systolic blood pressure (SBP), diastolic blood pressure (DBP) and heart rate were monitored during the orthostatic test after standing up. The male patients in the absent VEMP group presented a significant drop in their DBP at 1 min. after standing up (p<0.05) without any change in SBP. In the entire group of participants, a total of 19.6% of the patients in the absent VEMP group fulfilled the criteria for orthostatic hypotension (OH), which was significantly larger than the 8.6% of patients in the normal VEMP group and the 7.2% in the asymmetry VEMP group (P<0.05). Our results suggest that vestibular disorders due to the dysfunction of otolith organs provoke OH.
Audio-visual technological innovation has drastically changed our visual environments. Our visual system receives an overload of visual information in our daily lives. Visual stimuli, especially unsteady video images taken with shaking hands can induce motion sickness and cause nausea and headache as autonomic dysfunctions. We analyzed autonomic functions such as pupillary responses, heart rate, and blood pressure during movie presentations. Sympathetic hyperactivity was observed in the affected subjects. Pupillary responses signify autonomic activities clearly with non-invasive methods. We applied pupillometry for evaluation of stressed subjects and diagnosis of neurological diseases. We observed parasympathetic nervous dysfunction in those subjects. Evaluations of the relationship between visual and autonomic functions could be a potential marker for understanding the visual-autonomic systems.
Catecholaminergic inputs into the inner ear originate from the superior cervical ganglion (SCG). Alpha-adrenergic receptors (ARs) are located around the spiral modular artery and are involved in vasocontraction and cochlear blood flow. Beta 1-ARs in the strial marginal cells and vestibular dark cells have a regulatory role on endolymph production. Beta 2-ARs in the endolymphatic sac also control endolymph absorption. Therefore, stress-induced sympathetic nerve hyperactivity might promote adrenergic effects on the inner ear, resulting in the onset of sudden deafness and/or Meniere's disease. Beta 2-ARs show significant long-lasting up-regulation not only in the affected side of the vestibular ganglion (VG) but also in the healthy side, when a great imbalance exists between bilateral vestibular nuclei (VN) activities. Bilateral simultaneous labyrinthectomies have no significant effects on beta 2-AR expression in VG. This finding suggests that beta 2-ARs in the VG could play a neuro-plastic role in vestibular compensation. Further studies are needed to elucidate the molecular mechanisms in catecholamine and vestibular periphery-mediated vertigo.