Congenital nystagmus (CN) is known as an involuntary to-and-fro movement of the eyes characterized by a wide variation in waveforms ranging from jerk to pendular types. CN is presumed to be present at birth. In antiquity, midwives or shaman occasionally noticed CN. The first description of CN, popularly known in china as “shiji,” was made around 2000 years ago. Despite its various waveforms, people with CN do not develop visual symptoms and rarely complain of oscillopsia. CN can be idiopathic but is most likely caused by gaze stability, although some reports have suggested familial cases. No detailed mechanisms have been proposed to explain the generation of CN waveforms in people with CN in whom the vestibulo-ocular reflex (VOR) cannot be established. The vestibular time constant showed a good correlation between VOR and perception in normal subjects when assessed using perceptual measures. The time constant (TC) of decay of vestibular sensation in individuals with CN was half the duration of the TC found in normal subjects. Thus, individuals with CN have short vestibular time constants, probably due to changes induced in velocity storage processing by the persistent retinal image motion present in individuals with CN. There is a fascinating paper showing that FRMD7, also known as the CN gene, is necessary for optokinetic nystagmus (OKN) in humans and mice. In the retina of FRMD7-mutant mice, horizontal direction selectivity and asymmetry of inhibitory inputs to horizontal direction-selective retinal ganglion cells (HDSCs) are both lost. This could be a hidden essential characteristic of CN. HDSCs are responsible for horizontal OKN and project to the nucleus of the optic tract (NOT), and NOT, in turn, is related to the velocity storage mechanism, vestibular adaptation, and habituation. Inversion of OKN and suppression of nystagmus with eye closure are characteristics of CN. Both of these features can be explained by abnormalities in HDSCs. So, HDSCs can only play the role in the light. In the future, innovative ideas could help to elucidate the nature of CN.

　Lesion side and mean slow phase velocity of horizontal positional nystagmus (SPVH) were investigated in 35 patients with heavy cupula (HeC), consisting of 17 cases of lateral canal benign paroxysmal positional vertigo (BPPV)-canalolithiasis apogeotropic type (L-ca-apo) and 18 cases of L-BPPV―cupulolithiasis (L-cu), and 18 patients with light cupula (LiC). The Neutral position (NP), where the direction of horizontal nystagmus reverses, existed on the right-or left-ear-down head position in the supine position and was near the upright sitting position in the sagittal plane in the patients with HeC and LiC. In the HeC patients, the SPVH was significantly greater in the non-NP down position (n-NDP), compared with the NP down position (NDP), and was significantly greater in the supine position (SP) than in the prone position (PP). The ratio of SPVH in the n-NDP to the SP and the ratio of SPVH in the PP to the SP in the patients with L-ca-apo were significantly greater and lower than those in the patients with L-cu, respectively. In the LiC patients, the SPVH was significantly lower in the SP than the PP but was not significantly different between the n-NDP and the NDP. Taking Ewald's second law into consideration, the ratios of SPVH were not significantly different between the patients with LiC and the patients with L-cu. In HeC or LiC, when the direction of horizontal nystagmus in the SP reverses relative to that in the PP, the side of the NP when the patient is in a supine position indicates the lesion side. Asymmetrical responses in the head roll test do not always indicate the lesion side in patients with HeC and do not indicate the lesion side in patients with LiC. The weight of the affected cupula, the angle of the head rotation, the angle of the NP and Ewald's second law seem to determine the direction of the nystagmus and the SPVH. The ratios of the SPVH in the SP and the SPVH in the PP seem to be determined by Ewald's second law. The different SPVH ratios between the L-ca-apo and L-cu groups can probably be explained by the fact that the otoconia mass is in partial contact with the cupula in the patients with L-ca-apo, whereas the mass is in full contact with the cupula in the patients with L-cu. These differences in pathophysiology between LiC and L-cu patients seem to be responsible for the weight change of the cupula.

　Migraine and dizziness/vertigo are closely related. Recently, the diagnostic criteria for vestibular migraine have been reported. Patients with Meniere's disease often complain of migraine. Moreover, some patients complain of migraine and recurrent vertigo attacks with hearing symptoms, which are clinical characteristics of Meniere's disease. In these cases, distinguishing between Meniere's disease and vestibular migraine can be difficult. Thus, these patients can be reasonably assumed to have vestibular migraine/Meniere's disease Overlapping Syndrome (VMOS). In this report, we present the case of a 28-year-old woman with VMOS. The patient had been complaining of migraine, right-side hearing loss, and recurrent vertigo attacks since the age of 15 years. She reported having two different types of vertigo: intense vertigo lasting for several hours, and continuous dizziness lasting for several days. She was referred to our hospital to control her vertigo. Based on her symptoms, the patient was diagnosed as having VMOS. Subsequently, conventional prophylactic pharmacotherapy for migraine was prescribed, and vestibular rehabilitation was introduced. As a result of this treatment, her symptoms gradually improved. The presence or absence of hearing loss and the duration of vertigo attacks are key symptoms for the discrimination between vestibular migraine and Meniere's disease.

　Abstract: We report the case of a 14-year-old male patient with dizziness originating from multiple cerebral infarctions. He presented at our hospital with vertigo onset during a soccer game. He had a family history of collagen disease. Although a physical examination revealed a left-beating horizontal nystagmus upon a left gaze, a CT scan showed no abnormalities. He was diagnosed as having acute peripheral vertigo and was hospitalized in our department. On the second day of his admission, he developed a right eye adduction disorder and was referred to the neurology department. On day 3, an MRI revealed acute infarctions in the cerebellum, midbrain and crus posterus capsulae internae. Treatment with heparin and edaravone was immediately begun. On day 4, anisocoria and respiratory disturbance were noted; a second MRI was performed, revealing brain swelling. Although therapeutic hypothermia was initiated to prevent brain death, the patient's general condition gradually worsened and he died on day 16. A blood sample sent to another facility tested positive for lupus anticoagulant, suggesting a diagnosis of catastrophic antiphospholipid antibody syndrome. In patients presenting with acute vertigo, a head MRI should be immediately performed if a family history of collagen disease is present, even in pediatric cases.

　We report herein our trial using cervical vestibular evoked myogenic potentials (cVEMP) to screen for acute-onset nystagmus-free patients complaining of “dizziness” and “floating.” Each patient was placed in a supine position with his or her head elevated. Active electrodes were placed bilaterally on the sternocleidomastoid muscle, while the reference electrode was placed on the rostral lateral sternum. The stimulating sounds consisted of a “Click” (95 or 105 dBnHL) transmitted using insert earphones. The stimulation frequency was 5 Hz, 100 sweeps. Bilateral simultaneous stimulation was performed, and the results were recorded. A total of 108 patients ranging in age from 14 to 86 years old (average, 61.1±16.6 years) were examined. None of the patients had conductive hearing loss or spontaneous nystagmus. cVEMP responses are suppressive with an ipsilateral predominance, and neck muscle tension is indispensable for the implementation of this examination. However, muscle tension decreases with aging, as evidenced by an age-associated decrease in amplitudes as well as the prolongation of the latency times. Meanwhile, the VEMP amplitudes are increased to a greater extent by neck rotation than by neck elevation during recording. The advantage of head elevation to obtain better responses was found to burden the patients with continued muscle tension in the neck. Light insert earphones were therefore used to alleviate the patients' load. The number of sweeps was limited to 100 because repetitive stimuli fatigued the muscles, leading to poor responses. Stimulation was provided, and bilateral recordings were simultaneously made. Overall, 30.6% of the patients exhibited unilateral abnormal cVEMP findings, while 2.8% of the patients exhibited bilateral abnormal cVEMP findings; 15.7% of the patients had VEMP findings with a poor reproducibility. When the poor reproducibility group was compared with the normal response group, the average age of the poor reproducibility group was significantly older. In conclusion, abnormal VEMP test results were observed in over 30% of the patients who underwent testing. Bilateral cVEMP is useful as a primary test in patients without nystagmus who complain of dizziness and floating.

　Introduction: The diagnosis of dizziness is important because it is sometimes associated with fatal conditions such as cerebrovascular and cardiac diseases. We report several cases of “dangerous” dizziness that were initially referred to our otolaryngology clinic as peripheral dizziness and were subsequently found to be associated with central nervous system (CNS) and cardiac diseases.

　Subjects: Eight (3 male and 5 female) patients out of a total of 211 patients who visited our clinic between June 2016 and June 2017 were studied.

　Results: Six (2.8% overall) patients had CNS disorders and 2 (1.0% overall) had cardiac diseases. Four (50% of the studied patients) were referred to our clinic from the ER, and 4 (50% of the studied patients) were referred from the Department of Internal Medicine. Two (25% of the studied patients) of the patients complained of vertigo, and 6 (75% of the studied patients) complained of dizziness. Five (60% of the studied patients) of the patients had high blood pressure and cardiac diseases. All the cases had orthostatic symptoms.

　Conclusion: MRI examination was useful for the diagnosis of CNS disorders, but it also included false-negative DWI cases. The Schellong test was useful for the diagnosis of cardiac diseases. For accurate diagnosis and appropriate treatment, changes in symptoms and physical signs should be closely monitored and appropriate diagnostic tools should be applied in a timely fashion.

　The author presented recent topics concerning the clinical application of vestibular-evoked myogenic potential (VEMP). First, methods for detecting endolymphatic hydrops using cVEMP (cervical VEMP) were shown. Two methods, the glycerol cVEMP test and the cVEMP tuning property test, were introduced. Although the former is an orthodox method, it is time-consuming and can cause uncomfortable feelings, such as nausea or headaches. Although the latter method is easier, it does not provide information when subjects do not show responses to either 500-Hz or 1000-Hz tone bursts. Second, the application of oVEMP (ocular VEMP) to the physiological diagnosis of superior canal dehiscence syndrome (SCDS) was presented. Compared with oVEMP responses in healthy subjects, SCDS patients have lower thresholds and larger amplitudes in oVEMP, especially in response to air-conducted sound. Air-conducted sound oVEMP is very useful for the physiological diagnosis or screening of SCDS. The third topic was the combined use of VEMP and vHIT (video head impulse test) for the accurate diagnosis of vestibular disorders. While VEMP tests the otolith organ, vHIT tests the semicircular canal including the vertical canals. Therefore, the combined use of VEMP and vHIT can enable a more accurate diagnosis. As examples, the author presented two cases of episodic otolithic vertigo and vestibular neuritis.

　The postural control system coordinates sensory inputs from the vestibular, somatosensory and visual systems with outputs to the musculoskeletal system to maintain body balance. Posturography measures the changes in the center of pressure (COP) during an upright stance. Our group developed a foam posturography system, in which posturography is performed while standing on rubber foam, thereby changing the relative contribution of the somatosensory system. Our studies have shown that this foam posturography system is very useful for detecting unilateral as well as bilateral peripheral vestibular dysfunction. Furthermore, it is also useful for detecting dysfunction of the inferior vestibular nerve system as well as unilateral vestibular dysfunction at the chronic stage. A frequency analysis of the COP has been shown to be useful for characterizing the postural stability of patients with vestibular diseases and various neurodegenerative disorders. We compared the frequency characteristics of postural instability in patients with psychogenic dizziness, bilateral vestibulopathy, and spinocerebellar degeneration. Our analysis showed that patients with psychogenic dizziness exhibited an increase in power across frequencies<1Hz, patients with bilateral vestibulopathy exhibited an increase in power across a broad range of frequencies, and patients with spinocerebellar degeneration exhibited an increase in power across frequencies ranging from 2 to 4Hz. These results indicate that a frequency analysis of the COP is useful for differentiating among psychogenic dizziness, peripheral vestibulopathy and cerebellar diseases.

　The accumulation of neurophysiological knowledge and advances in electronic technology have enabled the recent development of novel examinations for vestibular function. One is the vestibular-evoked myogenic potential (VEMP), which has already been established as a functional examination for otolith organs. Here, as an application of VEMP, we will describe furosemide-loading VEMP, which is a new examination for the diagnosis of endolymphatic hydrops. The VEMP amplitude increases after furosemide administration in patients with Meniere's disease. Positive results are also seen in cases with occult endolymphatic hydrops that does not evoke symptoms. Another is the video head impulse test (vHIT), which enables vestibular examinations to be performed easily and quickly. The results of vHIT correspond with those of caloric testing in cases with vestibular neuritis. On the other hand, the results of vHIT do not agree with those of caloric testing in cases with Meniere's disease. Thus, vHIT cannot replace caloric testing in all patients with balance problems. However, the function of the vertical semicircular canal (anterior and posterior semicircular canal) can be evaluated using vHIT. To diagnose inferior vestibular neuritis, which is a new concept in vestibular disorders, vHIT and VEMP are required.

　After an acute unilateral loss of peripheral vestibular function, numerous oculomotor and postural deficits appear; these deficits can be subdivided into static and dynamic categories. Static signs are present without head movement, while dynamic signs are present only during head movement. Static signs include vigorous spontaneous nystagmus, which is mainly horizontal with a quick phase directed away from the affected ear, and postural symptoms such as falling to the affected side and difficulty standing and walking. These symptoms usually diminish or disappear entirely with no medical intervention. This recovery of normal function is due to the plasticity inherent in the central vestibular system even if the vestibular function on the affected side does not recover (vestibular compensation). In humans, vestibular compensation takes 3 to 5 days to begin and a month or more to reach a functionally useful level. Dynamic signs include depressed and asymmetrical vestibule-ocular reflex (VOR) and diminished VOR. Vestibular rehabilitation is known to be useful for the alleviation of dynamic signs after unilateral vestibular loss. The aim of vestibular rehabilitation is to promote vestibular compensation and sensory substitution by visual and somatosensory input. Moderate to strong evidence exists supporting the safety and efficacy of vestibular rehabilitation in managing unilateral peripheral vestibular dysfunction based on a number of high-quality randomized controlled trials. Moderate evidence also exists supporting the ability of vestibular rehabilitation to resolve symptoms and improve function within the mid-term. In this article, evidence for vestibular rehabilitation and the underlying mechanism of vestibular compensation, which is processed mainly by the commissural fibers connecting the vestibular nuclei on both sides of the medulla oblongata and by the vestibular cerebellum, will be introduced. The role of somatosensory input, which is processed in the spinal cerebellum, as a promoting factor for vestibular compensation will also be discussed.

　One of the hazards in performing vestibular rehabilitation therapy is the lack of an adequate evidence base. McDonnell and Hillier reported a large cohort study that summarized all the available articles regarding evidence-based vestibular rehabilitation therapy and found that only 29 out of 1586 articles were actually evidence-based. This was a striking result, and unfortunately none of the 29 evidence-based reports were from Japan. However, several applications for vestibular rehabilitation have recently been accepted by the Grants-in-Aid for Scientific Research program of the Japan Society for the Promotion of Science. Thus, evidence-based vestibular rehabilitation therapy has just started. This report will discuss how to perform evidence-based vestibular rehabilitation therapy.