Measurement of the subjective visual vertical (SVV) is clinically used as a method to assess the degree of dysfunction of the otolith, vertical semicircular canals, vestibular nerves, and central graviceptive pathways.

　In this short review, the author describes the history, basic neurophysiological findings, including the relation between the ocular tilt and bias of SVV, and interpretation of the examination data and clinical data.

　The tilt of SVV is a parameter of tonic afferent differences between the two labyrinths, similar to vestibular nystagmus, but SVV provides additional information, different from that obtained by nystagmus testing, on the labyrinth function.

　In clinical practice, however, measurement of SVV is not so widely used as a clinical test. It is expected that SVV testing will be conducted in more institutions in clinical practice as a complementary test to nystagmus testing.

　This study was aimed at (1) determining the risk of falls in patients with chronic dizziness/vertigo using the Timed Up and Go test (TUG), Dynamic Gait Index (DGI), Functional Gait Assessment (FGA), and Activities-specific Balance Confidence (ABC) scale, and (2) investigating the correlations and agreements among the measurements results of assessment by the aforementioned methods in these patients.

　A total of 52 patients with dizziness/vertigo were included in the study, and the risk of falls in these patients was evaluated by the TUG, DGI, FGA, and ABC scale. We analyzed the correlations and agreements in the fall risk assessed by the aforementioned methods using Spearman's rank correlation and kappa statistics.

　Of the 52 patients, 11 (21.2%), 26 (50%), 29 (55.8%), and 18 (34.6%) patients were assessed as being at a risk of falls by the TUG, DGI, FGA, and ABC scale, respectively. The results of the assessments by the above methods showed significant good correlations and agreement. However, the kappa coefficients for some results were low (TUG-DGI: k=0.423, TUG-FGA: k=0.351, TUG-ABC scale: k=0.299, DGI-FGA: k=0.885, DGI-ABC scale: k=0.385, and FGA-ABC scale: k=0.294).

　Risk factors for falls in patients with dizziness and vertigo include disturbances of psychological balance and gait. Multiple methods to assess the fall risk may yield more accurate results than assessment by one method alone.

　Meniere disease was included in the national registry of Designated Intractable Diseases by the Ministry of Health, Labour and Welfare (Japan) in 1974. Therefore, it would be desirable for medical expenses incurred towards treatment of Meniere disease to be subsidized by public funds. However, the Act on Medical Care for Patients with Intractable Diseases (Intractable Diseases Law) is not yet applicable to Meniere diseases, and there is, at present, no public medical expenses subsidy at the national level. Kagawa Prefecture designated Meniere disease as a specific disease treatment research project (designated by the prefecture) in June 1980, and has been providing public medical assistance to patients with Meniere disease. After the Intractable Disease Law was enacted, Meniere disease was specified as a designated intractable disease in Kagawa prefecture, and medical expenses subsidy has been continued for Meniere disease, as well as other designated intractable diseases included in the national registry by the Ministry of Health, Labour and Welfare (Japan). Since 2010, the number of recipients of subsidy for the treatment of Meniere disease has ranged from 15.0 to 19.6 per 100,000 (male 1: female 2.7), comparable to the corresponding figure in previous epidemiological reports.

　The public medical expenses subsidy project for Meniere disease in Kagawa Prefecture has been carried out smoothly for over 30 years, and it was confirmed that a sustainable public medical expenses subsidy project for Meniere disease could be continued. Meniere disease is included in the national registry of designated intractable diseases and is expected to be eligible for public medical expenses at the national level.

　Vestibular dysfunction in Pendred syndrome is inconsistent and variable. A mouse model of Pendred syndrome (Slc26a4 ^Δ/Δ mice) is known to manifest variable degrees of vestibular dysfunction, as evidenced by gait unsteadiness, circling behavior, and head tilting. Scanning electron microscopic studies of the vestibular end organs have demonstrated abnormally enlarged otoconia, while the vestibular hair cells looked normal for 2 months after birth. In this study, we performed X-ray computed microtomography (microCT) at 10-micron resolution with three-dimensional image reconstruction of the otoconia as well as the bony labyrinth, to elucidate the etiology of the equilibrium disturbance observed in the Slc26a4 ^Δ/Δ mice. The otic capsules of the Slc26a4 ^Δ/+ and Slc26a4 ^Δ/Δ mice were imaged by microCT at 1 day, 8 days, and 3 months of age. Multiplanar reconstructed images were used to calculate the width of the saccule and utricle, and delineate the shape, size, and location of the otoconia. The ossicles, osseous labyrinth, and otoconia were clearly visualized by microCT. The Slc26a4 ^Δ/Δ mice exhibited an enlarged saccule and utricle as compared to the Slc26a4 ^Δ/+ mice. In the utricle of the Slc26a4 ^Δ/Δ mice, nearly 20 giant otoconia were discretely distributed on P8. The number of otoconia decreased with age. In the saccule, otoconia were fewer in number than that in the utricle, or altogether absent, on P8. No ectopic otoconia were observed in any of the semicircular canals. We succeeded in non-destructive delineation of the giant otoconia in the Slc26a4 ^Δ/Δ mice by microCT, with extremely few artifacts. We believe that these results will be useful for elucidating the etiology for equilibrium disorder in Pendred syndrome.

　To evaluate the influence of somatosensory input on the vestibulo-ocular reflex (VOR), we assessed 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, 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) touch condition: the subjects (n=26) were told to touch the handle with their right index fingers; (2) bite condition: the subjects (n=24) were told to perform maximum voluntary tooth clenching. The change in the VOR gain did not differ significantly across any of the conditions, including EVAR or OVAR under both stimulation 2 conditions. In our previous study, we proposed that arthrokinetic input (i.e., arm movement) had an additive effect on the VOR, but in the present study, light-touch input had no influence on the VOR.

　Objective: To investigate the features of the Post Earthquake Dizziness Syndrome (PEDS) in Hokkaido by a questionnaire survey.

　Methods: A total of 50 patients with any kinds of vestibular disorders who experienced the huge earthquake in Hokkaido on September 6, 2018, were enrolled in this study. The characteristic symptoms in the patients with PEDS were investigated by a questionnaire survey.

　Result: Of the 50, 19 patients (38.0%) reported suffering from PEDS. The number of women with PEDS was significantly higher than the number of men (53.6% vs. 18.2%). There was no significant correlation between the age and the presence risk of PEDS. The typical symptom of PEDS was dizziness in the sitting position while indoors, the symptom disappearing within a minute.

　Conclusion: Patients with PEDS were detected after the earthquake in Hokkaido, similar to the case after other huge earthquakes in Japan. It is speculated that disturbances of the vestibular organs and psychological stress underlie the development of PEDS.

　Vestibular function testing is very important for establishing the correct diagnosis of vertigo and dizziness, and is especially helpful for isolating the affected side and the responsible lesion. Until the end of the Showa period, caloric nystagmus was the gold standard for this examination, but it was inadequate to examine the otolith function. During the Heisei period, vestibular evoked myogenic potential (VEMP) and video head impulse test (vHIT) were introduced, which enable detailed examination of the functions of the inner ear and vestibular nerve. In these examinations, cervical VEMP (cVEMP) is used to evaluate the sacculus, and inferior vestibular nerve function, which examination is used to evaluate vestibular neuritis, acoustic neuroma, and superior semicircular canal dehiscence. Until now, endolymphatic hydrops was detected using glycerol-or furosemide-loaded cVEMP; however, these tests have side effects, such as headache, and take several hours to perform. To address these concerns, we introduced the tuning property test and confirmed its diagnostic usefulness. The tuning property test is very useful because it does not require any drugs and can be completed in a short time. During the Reiwa period, additional research on the properties and clinical usefulness of the tuning property test are needed.

　For over a decade, grading of endolymphatic hydrops, a disease of the inner ear, has been achieved by using contrast-enhanced MRI. We compared the positivity rates between contrast-enhanced MRI and neuro-otological examinations.

　Contrast-enhanced MRI showed 83% sensitivity and 100% specificity for the diagnosis of lesions in the cochlear area. However, for the diagnosis of lesions in the vestibular area, the sensitivity was 87.5% and the specificity was 12.5%. On the other hand, the diagnostic sensitivities of neuro-otological examinations were 60%, 20%, 0%, and 100% for furosemide VEMP, furosemide VOR, glycerol test, and electro-cochleogram.

　These results suggest that contrast-enhanced MRI is the most valuable examination for the diagnosis of endolymphatic hydrops.

　There are patients with floating dizziness who do not show abnormalities in current vertigo balance tests. We developed a clinical examination to quantify gravity perception as a first step to test our hypothesis that a gravity perception disturbance is the cause of floating dizziness. The gravity sensitivity can be measured accurately by adding the head tilting condition to the original subjective visual vertical (SVV) test. We named this test the Head Tilt SVV (HT-SVV). The most important measurement item in HT-SVV is head tilt perception gain (HTPG). HT-SVV measurements in 329 healthy subjects yielded an average value and standard deviation of 1.02±0.12 and a reference value of 0.80-1.25 for HTPG, and a difference between the left and right HTPG of 4.7±3.7%, i.e.,<10.0%. We could not detect age-related changes in gravitational sensitivity by the original SVV, but found that HTPG, determined by HT-SVV, increased with age. A significantly higher rate of subjective dizziness was noted in patients who tested positive in the HT-SVV than in those who tested negative among patients who developed floating dizziness after BPPV. We would like to clarify the clinical significance of the test method and establish the concept of gravitational susceptibility disorder, although a number of relevant issues still remain to be clarified.

　Several tools are available for the evaluation of nystagmus or eye movements, such as Frenzel glass, electronystagmography (ENG), and infrared video goggles. Although ENG is used as a quantitative examination for recording eye movements, it does not permit the recording of the torsional component of nystagmus. Videooculography (VOG) provides evaluation of all the three-dimensions of eye movements, including of the horizontal, vertical and torsional components. In addition, recent technological developments have improved VOG as a research and clinical tool. Progress has been made in the investigational capability of VOG, including the possibilities of performing quantitative evaluation of nystagmus, the visual stimulation test, filing system linkage, high-speed recording, and the video head impulse test (vHIT).