The most important histopathological finding in patients with Ménière's Disease (MD) is endolymphatic hydrops (EH). In 1938, Hallpike in London first reported EH in the temporal bones of two cases of MD. In the same year, Yamakawa of Osaka independently discovered EH in the temporal bone specimen of his colleague who suffered from MD. In 2007, Naganawa and Nakashima of Nagoya were the first to visualize EH in patients with MD in MR images obtained using Siemens 3T MRI with a 32ch head coil after intratympanic administration of 1/8-diluted gadolinium (Gd). In 2010, EH imaging was successfully accomplished after intravenous administration of a standard dose of Gd.

　In the chronic course of MD, the vertiginous episodes improve, but both the vestibular and hearing functions deteriorate. However, the details of how EH behaves in this process remains unclear, and in this short review, the author describes the details of how EH behaves during this process. Furthermore, the author also describes delayed endolymphatic hydrops (DEH), which is a secondary form of EH, and other related current findings.

　This study is aimed at exploring how the subjective visual vertical (SVV) might vary depending on the method used to determine the vertical positions. Original equipment devised by the author was used in this study (hereafter, SVV investigation equipment). Study participants spun a wheel in order to determine the vertical position of an axis presented to them as an illuminated pillar in a dark room. Participants were asked to perform the task six times during the study. The results reflect their averages, with a + indicating the results that tilted towards the right. In 20 healthy participants, the results of the SVV test obtained with the subjects using their dominant hands to adjust the angle were compared with those obtained with the subjects using their non-dominant hands. In 23 healthy participants, the results of SVV test obtained with the subjects using their hands to adjust the angle were compared with those obtained with having the subjects answer yes/no to the presented angle (12 different patterns of tilted markers from 0 to ±5 degrees). In another 20 healthy participants, the results of the SVV test obtained with the subjects performing the test with both eyes open were compared with those obtained with the subjects performing the test using either eye. All the results obtained by the different methods were correlated with each other. There was also no difference in the actual measured angle between the test methods except for that between the tests conducted with the patient using the dominant and non-dominant hands. Our present study indicates that, the characteristics of SVV deviation can be estimated correctly even if the measurement method varies slightly, although it is better not to change the method when performing quantitative or temporal evaluation.

　Benign paroxysmal positional vertigo (BPPV) is the most common form of peripheral vertigo. It can be caused by debris in the semicircular canal of the ear. In regard to the location of the debris in the affected semicircular canal, sequential movement of the patient's head in the canalith repositioning procedure can cause the debris to move from the semicircular canal to the utricle. There is evidence that the canalith repositioning procedure is a safe, effective treatment for BPPV, but busy doctors are not always capable of performing of this procedure for all applicable cases. Therefore, we examined whether performance of the canalith repositioning procedure by well-trained nurses under the supervision of a doctor might be effective. We chose the Epley manoeuver as the canalith repositioning procedure. The results revealed that the period until resolution of dizziness was significantly shortened and the cure rate improved significantly. Therefore, we concluded that the outcomes of nurses' assistance in the Epley manoeuver are favorable. Transferring some of the duties of doctors to nurses would reduce the burden on doctors and allow them to focus on diagnosis and treatment that only doctors can handle. Consequently, task shifting of doctor's work to nurses under the supervision of a doctor can be considered in many aspects of health care.

　Acute low-tone sensorineural hearing loss (ALHL) has a relatively good prognosis; however, cases of recurrent cochlear symptoms and cases of transition to Meniere's disease have also been reported. In this study, we investigated cases of relapse of ALHL and cases of transition from ALHL to Meniere's disease among patients with ALHL who visited our department.

　The subjects were 38 patients with ALHL who had undergone otolaryngology-head and neck surgery at Nippon Life Hospital during the 2-year period from July 2016 to June 2018.

　There were six cases of ALHL relapse (atypical cases of Meniere's disease-cochlear type), the hearing prognosis after the relapse improved in three cases and remained unchanged in the remaining three cases. There were seven cases of transition to Meniere's disease (cases definitively diagnosed as Meniere's disease), and the hearing prognosis after the transition improved in three cases and deteriorated in the remaining four cases. In addition, the symptom of dizziness noted at the time of the transition disappeared following the improvement in five cases, while mild subjective dizziness persisted in the remaining two cases.

　In clinical practice, ALHL is considered as acute sensorineural hearing loss, similar to sudden hearing loss at the first onset, as an atypical case of Meniere's disease when the hearing loss recurs, and as a certain case of Meniere's disease when recurrent dizziness occurs. It is useful to understand the disease as a spectrum of pathological conditions.

　With regard to treatment, initial ALHL can be managed with the same approaches as those for acute sensorineural hearing loss, and steroid use according to the usual treatment for sudden hearing loss. On the other hand, both cases of recurrence and those of transition involve endolymphatic hydrops, and it would be appropriate to administer diuretics containing isosorbide for these cases.

　ALHL has not received much attention until now, because of its good prognosis in Japan. We expect that the overall picture of this condition, including its pathophysiology, will be further investigated.

　We investigated the risk factors for vertigo from the results of health checkups conducted in Yakumo town.

　The subjects of this investigation included 525 persons (299 women and 226 men), aged 40 to 88 years (average 63.78 years). Among these, 397 persons (75.6%) had no vertigo, 116 persons (22.1%) had vertigo sometimes, and 12 persons (2.3%) suffered from vertigo frequently. Ninety-four women (31.4%) and 34 men (15.0%) had vertigo. Twenty-one (51.2%) of the 41 women in their 40s had vertigo. Logistic regression analysis revealed that subjective hearing loss, a low value of the mean corpuscular hemoglobin concentration (MCHC), headache, high level of serum creatinine and frequent urination were significantly associated with the risk of vertigo, after adjustments for age and sex. Listening difficulties in conversations between four or five people were reported more frequently than those in one-to-one conversations. Anemia should be considered in the differential diagnosis of vertigo. In the diagnosis of vertigo, information about the presence/absence of headache and the status of the headache, if any, may be necessary. In our study, migraine and headache on the ipsilateral side were associated with vertigo, but bilateral headache was not associated with vertigo. Our analysis, did not reveal smoking, drinking, exercise habit, sleep time, body mass index (BMI), body fat percentage, hemoglobin A1c, blood glucose, serum triglyceride, serum LDL cholesterol, or serum HDL cholesterol as being significantly associated with the risk of occurrence of vertigo, after adjustments for age and sex.

　Rotation testing was performed to evaluate the functions of the vestibular system by applying a rotational stimulation to a subject and observing the eye movements caused by the vestibulo-ocular reflexes (VORs). VORs comprise the semicircular-ocular reflex (ScOR) and the otolith-ocular reflex (OOR). When the subject's lateral semicircular canal is positioned horizontal to the ground and earth vertical axis rotation (EVAR) is applied, the lateral semicircular canal is stimulated by rotational acceleration, resulting in eye movements caused by the ScOR. In contrast, with off-vertical axis rotation (OVAR), the direction of gravitational acceleration changes continuously during rotation, which simultaneously stimulates the otolith organ. The resultant eye movements are caused by both the ScOR and the OOR. In previous studies, the application of conflicting visual vestibular stimulation using a flat screen under EVAR conditions did not show a significant change in the VOR gain after stimulation. In the present study, we applied conflicting visual vestibular stimulation (-1 stimulation, ×2 stimulation) using a flat screen under OVAR conditions and compared the VOR gain before and after stimulation. No significant change in the VOR gain was observed before and after ×2 stimulation; however, a significant decrease in the VOR gain was observed after -1 stimulation. These results were obtained due to the effects of tilt suppression and because the conflicting visual vestibular stimulation we used was an appropriate form of stimulation to elicit the OOR.

　While various methods of vestibular rehabilitation have been reported for equilibrium disturbances, the effects of tilt suppression and whether the stimulation used for vestibular rehabilitation is an appropriate form of stimulation need to be considered.

　In the United States, physiotherapists play an important role in the treatment of dizziness, and evidence-based vestibular rehabilitation therapy (VRT) is often adopted in medical settings. VRT has also been used traditionally in Japan, but is mostly administered by physicians. Since 2015, we have been treating patients with intractable dizziness in collaboration with physiotherapists, laboratory technicians, nurses, and a clinical psychologist as a one-team medical care approach. Herein, we propose that collaborating with physiotherapists enables us to evaluate fall risk, dynamic balance, and gait of patients with chronic unilateral vestibular hypofunction (CUVH) and to offer supervised VRT. In CUVH patients who received individualized VRT supervised by physiotherapists as a supplement to home exercises, the scores of Dizziness Handicap Inventory, Dynamic Gait Index, and Functional Gait Assessment improved significantly at four weeks after the start of the intervention as compared to the scores at the baseline. On the other hand, no significant improvements were seen in the group of CUVH patients who performed only home exercises. Therefore, we conclude that collaboration with physiotherapists may improve the quality of the evaluation and treatment of patients with dizziness.

　The detrended fluctuation analysis (DFA), which is a fractal analysis, has recently been used in the biological field. We investigated the difference in the DFA scaling index between patients with unilateral vestibular disorders (UVD) and healthy adults using time-series data from the left-right and front-back directions of the center of pressure (COP) with closed legs and open/closed eyes. The patients with UVD showed a lower long-range scaling index (α_long) in the time domain in the left-right direction with the eyes closed as compared to the healthy adults. There was a significant negative correlation between the total trajectory length and the short-range scaling index (α_short) in patients with UVD in both the left-right and front-back directions (r=0.64, r=0.68, p<0.05). Vestibular rehabilitation (VR) increased the α_long of the COP time series with the eyes closed in the left-right direction in patients with UVD. VR may be most effective for cases of UVD with higher values of α_long. On the other hand, VR may be partially effective for patients with UVD with lower values of α_long and patients with bilateral vestibular disorder (BVD) with residual vestibular function. We suggest that the values of α_long in the DFA of the COP time series with eyes closed provides useful information for VR for dizzy patients with UVD and BVD.

　Coherent integration of multisensory inputs, especially visual, vestibular and somatosensory cues, is essential for appropriate self-motion perception, and sensory mismatch (i.e., sensory conflict) among different sensory information during body motion induces vertigo and instability of posture. To elucidate the cortical roles in the maintenance of postural stability under sensory conflict situations, we recorded the cortical hemodynamic activity using near-infrared spectroscopy (NIRS) while the subjects underwent the sensory organization test (SOT) protocol that systematically disrupts sensory integration processes. In healthy subjects, we found activation in the temporoparietal junction (TPJ), the posterior parietal cortex (PPC), the premotor cortex (PMC), and the supplementary motor area (SMA) under various conditions. The activation patterns of these cortical areas in response to specific combinations of SOTs suggested that 1) the TPJ might be involved in the process of sensory reweighting; 2) the SMA and PMC might be essential for the voluntary cortical motor control in sensory conflict; 3) activation of the PPC might be involved in the updating and computation of spatial orientation in sensory conflict. In two patients with chronic vertigo induced by unilateral vestibular neuritis, the PPC, SMA and PMC were activated under SOT 3 or 4 and the SOT condition that activated these regions the most differed among subjects, suggesting that the dependent sensory input (i.e., visual or somatosensory input) to maintain the standing balance in sensory conflict situations might differ among patients with chronic vertigo. In recent studies, the neurofeedback therapy using fNIRS has received attention as a novel rehabilitation technique for post-stroke or psychiatric patients. We propose that the neurofeedback therapy using fNIRS will become a promising therapeutic tool for patients with intractable chronic vertigo.