Dizziness may be caused by multiple factors including unknown reasons. It is well known that insomnia is associated with increased psychological symptomatology and perceived stress, higher predisposition to arousal, and greater impairments to quality of health. The relationship between dizziness and stress is well documented, but that between dizziness and insomnia is unclear. In this series, we focus on Ménière's disease, which is characterized by fluctuating and progressive hearing loss, aural fullness, tinnitus, and intermittent attacks of vertigo, an illusory sensation of movement resulting from dysfunction of the labyrinth and cochlea, to investigate the relation between sleep disorders and dizziness. In our previous report, we first found that the sleep quality of Ménière's disease patients was impaired. Ménière's patients have a longer total sleeping time, lack of deep sleep stages, increased arousal, and the combination with obstructive sleep apnea syndrome and/or periodic limb movement disorder was occasionally noted. Poor quality of sleep may cause additional stress and lead Ménière's disease patients into a negative spiral of symptoms. Furthermore, poor sleep quality may result in Ménière's disease patients being refractory to medical management. Therefore, prospective treatment focusing on the sleep disorders of, not just Ménière's disease but possibly also dizziness symptoms, may become an additional new strategy for terminating the negative spiral of symptoms and reduce exacerbation of the affected patient's conditions.
Vestibular evoked myogenic potentials which are induced around the eyes are known as ocular vestibular evoked myogenic potentials (oVEMPs) and are useful for the clinical examination of vestibular function. Cervical vestibular evoked myogenic potentials (cVEMPs) have been used as a test of the vestibulo-collic reflex, particularly the sacculo-collic reflex. In Ramsay Hunt syndrome, facial palsy of the eighth cranial nerve spreads from the geniculate ganglion via the vestibulofacial and vestibulocochlear anastomoses. Other studies have also reported that vertigo in patients with Ramsay Hunt syndrome is mostly induced by superior vestibular neuritis. We identified oVEMPs in patients with unilateral facial palsy and analyzed the association of oVEMPs with clinical usefulness, recovery of facial palsy, and pathology of Ramsay Hunt syndrome. Seventeen patients with facial palsy were enrolled in this study. There were 6 cases of Bell's palsy and 11 cases of Ramsay Hunt syndrome. Vertigo in patients with Ramsay Hunt syndrome was induced by superior vestibular neuritis rather than inferior vestibular neuritis, as was indicated by the frequent impairment of oVEMPs. There was a tendency for patients with a low electroneurography (ENoG) value, and patients who had improved slowly, to show abnormal oVEMPs.
Up- and down-beating nystagmus reminds us of central vestibular deficits, such as spino-cerebellar degeneration and Arnold-Chiari malformation. However, in our routine medical care, we frequently meet cases with vertical nystagmus, which are finally diagnosed as being a certain peripheral vestibular deficit. In this manuscript, we studied the medical records of cases visiting our neuro-otological specialty outpatient clinic since January 2011 to April 2015 (1,770 cases), and detected patients who exhibited vertical nystagmus in ENG recordings (58 cases). Detailed diagnosis, clinical findings including VOG recordings, and the course of the nystagmus were verified. These consisted of 27 with central deficits, 18 with peripheral deficits, accompanied by 2 with vestibular schwannomas and 11 without a confirmed diagnosis. Eighteen cases demonstrated vertical nystagmus on ENG, reconfirmed with VOG recordings in their clinical courses, which included 6 with peripheral deficits. Findings of several cases support an inclusion of a rotational component of nystagmus, which was interpreted as vertical on ENG. On the other hand, in some cases, possible pure-vertical nystagmus caused by a peripheral vestibular deficit was also suggested.
We investigated otolith function using the subjective visual vertical (SVV) in 54 patients with persistent geotropic positional nystagmus (Light cupula), 30 patients with persistent apogeotropic positional nystagmus (Heavy cupula) and 45 healthy subjects. To compare benign paroxysmal positional vertigo (BPPV), SVV was also measured in 56 patients with posterior canal canalolithiasis (PC) and 38 patients with lateral canal canalolithiasis (LC). Patients attended the clinic within 1 week after the onset of vertigo, and the SVVs were examined prior to treatment. The affected sides of Light cupula and Heavy cupula were estimated based on the neutral position at which the horizontal nystagmus direction was reversed. The average SVV toward the affected side showed significantly higher values, in this order: Light cupula>LC/PC>healthy subjects and Light cupula>Heavy cupula. Otolith dysfunction could be demonstrated on the affected side in Light cupula, whereas Heavy cupula exhibited a lesser degree of otolith dysfunction. The average SVV value toward the affected side of 0.9 is recommended as a cut-off value for Light cupula (sensitivity: 0.75, specificity: 0.86). The average SVV value>1.4 toward the affected side is also recommended as a cut-off for the detection of otolith dysfunction in Light cupula, PC and LC (specificity>0.93).
It is considered that the dawn of scientific investigation into human postural mechanism dates back to the 17th century when Borelli tried to measure the gravity line in humans. Until the end of the 18th century, balance sensation was considered as something like a ghost sensation. However, in the early 19th century, Flourens (1828) clarified the function of the vestibular organs, followed by Romberg's discovery of the visual contribution to the postural control mechanism (1840). The cybernetic approach has subsequently gradually been introduced. Vierordt (1860) was the first to have had made posturographic recordings and showed that human posture is maintained by small incessant movements. As for the introduction of the postural reflex mechanism, Magnus and Sherrington's contribution was epoch-making. However Fukuda's subtle detailed observation of human posture indicated those reflexes can be observed in daily life. With the introduction of the computer, analysis of movements of the body center of gravity developed remarkably worldwide, especially after World War II. Kapteyn was the first to introduce the world standard for stabilometry in 1981 at the 6th international postulography meeting in Kyoto. Based upon this standardization, Japan has manufactured stabilometric instrumentation and from 1994, this examination was approved for coverage by the Japanese Health Insurance system. However this standardization has not been fully used in all countries. The establishment of a global standard is mandatory to enable all discussions to be on the same page, and to allow sharing important research results on stabilometry.
In 1969, the International Society of Posture and Gait Research (ISPGR) was established as an international association devoted to basic and clinical research into posture and gait. In 1983, international standards for clinical stabilometry were proposed by the ISPGR committee and published in an academic journal. These standards are widely accepted and are referred to in many countries. Japanese industrial standards for stabilometry were established in 1987, and Japanese standards for clinical stabilometry were produced by the Japanese Society for Equilibrium Research in 1988 based on the ISPGR standards. Stabilometry has been covered by the Japanese health insurance system since 1994. However, revised international standards were proposed at the 19th congress of the ISPGR in Bologna, and the discussions about such revisions are ongoing. In 2012, a proposed new set of standards was published in an academic journal by an Italian group. These standards were markedly different from the original ISPGR standards and the Japanese standards in terms of mechanical accuracy, precision, and sampling frequency. In 2014, a survey concerning the standardization of clinical stabilometry was carried out among the countries that have signed up to ISPGR by the informal Committee for the Standardization of Clinical Stabilometry. Recently, a French group devised another set of standards, which might become established in France. These standards are markedly different from the Japanese standards. Sudden major changes in the standards for clinical stabilometry are not considered desirable in Japan. In this paper, I would like to describe global trends in the standardization of clinical stabilometry and propose a way that Japan can deal with marked changes in international clinical stabilometry standards.
The foam posturography analysis system is useful for preliminary assessment of peripheral vestibulopathy. Body sway measured while standing on foam rubber with the eyes closed can increase in patients with vestibulopathy, because the role of vestibular inputs becomes more prominent under this condition. The Romberg's ratio and the foam ratios (ratios of measured parameter with to without the foam rubber) might indicate visual and somatosensory dependence in standing posture, respectively. We have performed clinical studies using the foam posturography analysis system. We proved the effect of the dysfunction of the inferior vestibular nerve system, which was detected by cervical vestibular evoked myogenic potentials, on postural stability. We suggested that body sway in patients at the chronic stage with poor recovery of peripheral vestibular function remained increased. We revealed that once a patient with vestibular neuritis passed the acute phase of the vertigo attack, age and residual vestibular function were important to maintaining posture. Foam posturography is expected to make a great contribution to both clinical examination and clinical research.
The Body Tracking Test (BTT) is a testing method of the dynamic body balance function wherein movement of the center of pressure (COP) in accordance with a moving visual target stimulus is examined to evaluate the tracking function of the body. We developed an evaluation method for BTT and a visual feedback test, which evaluates dynamic body balance functions using stabilometry. We also developed a method called the 10-grade evaluation of tracking ability. We investigated age changes in 516 healthy people using our 10-grade evaluation of tracking ability. The results enabled us to see the growth and age-related changes. The tracking axis by principal component analysis of the antero-posterior (AP) BTT was not parallel to the Y-axis and the tracking axis of the lateral BTT was not parallel to the X-axis. We investigated relationships with the dominant leg in human subjects to investigate the cause of changes in the inclination axis. The AP BTT in the right-foot dominance group showed a clockwise tilt whereas the group with left-foot dominance had a modest counter-clockwise tilt delineated by primary component analysis. This difference was found to be significant with the independent t test (p<0.0001). The subjects were patients who had been diagnosed as having vestibular neuronitis. Although gaze nystagmus was noted, inspection was enforced when a standing position posture was possible. In the antero-posterior (A-P) BTT, the direction of body sway average center displacement of X (cm) was ascertained. Deviation was seen in the affected side with stabilometry. Deviation was seen in the unaffected side with the antero-posterior (A-P) BTT. In the visual feedback test, the differences in size of the display circles were examined. Based on the results, a diameter of 2.5cm was considered appropriate, and clinical applications based on this consideration have started.
The conventional approach for evaluating postural balance with a stabilometer involves analysis of parameters such as mean velocity, length of sway path and sway area. Evaluation of these parameters is very important in assessment of the degree of the balance disorder, but they have not been applied to diagnose lesions of balance disorders. Because the sensorimotor control of maintaining balance during standing involves complex mechanisms of integrating multiple sets of information, it is difficult to clarify the characteristics of balance disorders derived from the input of each organ. Another approach for evaluating postural balance is based on nonlinear time series methods including fractal analysis. We used detrended fluctuation analysis (DFA) on stabilometric time series data. The DFA scaling exponent quantifies fractal-like autocorrelation properties and the complexity of the signals. The aim of this study was to investigate postural control strategy in the elderly and patients with balance disorders. Thirty-eight healthy subjects, 50 patients with unilateral vestibular dysfunction (UVD), 15 patients with cerebellar ataxia (CA) participated in this study. DFA scaling exponents can be divided into the short-range (α short) and long-range (α long) scaling components. The value of α long in the healthy subjects was nearly close to 1 (time series data of α=1 corresponds to 1/f noise). Compared to 13 young adults (23-38 years), the value of α long did not show significant differences in 19 young-elderly but was reduced in 14 late-elderly. Compared to the healthy subjects, the value of α long did not show a significant difference in patients with UVD and reduced significantly in patients with CA. The value of α long of patients with UVD in the acute stage was less than 1, but that of the patients with UVD in the subacute stage significantly increased and showed nearly 1. The value of α long of DFA may be a functional indicator of the attitude control system.