Chisato Fujimoto

Assessment of diagnostic accuracy of foam posturography for peripheral vestibular disorders: analysis of parameters related to visual and somatosensory dependence.

OBJECTIVES Simple tests to detect peripheral vestibulopathy might be practically useful before conducting elaborate examinations. The purpose of this study was to assess the diagnostic accuracy of foam posturography for peripheral vestibulopathy, with emphasis on visual and somatosensory dependence. METHODS Two-legged stance tasks were conducted in patients with unilateral (n=68) and bilateral (n=16) vestibulopathy and healthy controls (n=66), under four conditions; eyes open with and without the foam rubber, and eyes closed with and without the foam rubber. RESULTS The values of six parameters; the velocity of movement of the center of pressure (COP) and envelopment area tracing by the movement of the COP in eyes closed/foam rubber, the Rombergs ratios of velocity and area with foam rubber, and the foam ratios (ratios of a measured parameter with to without the foam rubber), of velocity and area in eyes closed, were significantly higher in unilateral and bilateral vestibulopathy compared with the control (p<0.001). The area under the receiver operating characteristic curve for the Rombergs ratio of velocity with the foam rubber was the largest. CONCLUSIONS Foam posturography detected high levels of visual and somatosensory dependence in patients with vestibulopathy. SIGNIFICANCE Foam posturography is useful for preliminary assessment of possible peripheral vestibulopathy.

Ocular vestibular-evoked myogenic potentials (oVEMPs) require extraocular muscles but not facial or cochlear nerve activity

OBJECTIVES Cervical vestibular evoked myogenic potentials (cVEMPs) have been found to be useful for clinical testing of vestibular function. Recently, investigators showed that short-latency, initially negative surface EMG potentials can be recorded around the extraocular muscles (oVEMPs) in response to air-conducted sound (ACS), bone-conducted vibration (BCV), and head taps. Although these evoked potentials, which are located around the eyes, most likely originate primarily from the otolith-ocular pathway, the possibility of contamination by other nerve activities cannot be completely eliminated. The purpose of the present study was to clarify the origin of oVEMPs by examining these possibilities using clinical findings. METHODS Twelve healthy subjects and 15 patients were enrolled. Of the 15 patients, 3 patients had undergone exenteration of the unilateral intraorbital contents, one had undergone exenteration of the right eyeball with preservation of extraocular muscles, 5 had facial palsy, and 6 had profound hearing loss. ACS and/or BCV were used in these subjects. RESULTS Exenteration of the unilateral intraorbital contents resulted in absence of myogenic potentials on the affected side. On the other hand, exenteration of the eyeball with preservation of extraocular muscles did not have a major impact on the responses. There were no significant differences in the waveforms between healthy subjects and patients with facial palsy or profound hearing loss. CONCLUSIONS The results suggested that short-latency, initially negative evoked potentials recorded below the eyes are not affected by cochlear or facial nerve activities and are dependent on the presence of extraocular muscles. SIGNIFICANCE This study provides the evidence that oVEMPs originate from exraocular muscles activated through the vestibulo-ocular pathway.

Oxidative Stresses and Mitochondrial Dysfunction in Age-Related Hearing Loss

Age-related hearing loss (ARHL), the progressive loss of hearing associated with aging, is the most common sensory disorder in the elderly population. The pathology of ARHL includes the hair cells of the organ of Corti, stria vascularis, and afferent spiral ganglion neurons as well as the central auditory pathways. Many studies have suggested that the accumulation of mitochondrial DNA damage, the production of reactive oxygen species, and decreased antioxidant function are associated with subsequent cochlear senescence in response to aging stress. Mitochondria play a crucial role in the induction of intrinsic apoptosis in cochlear cells. ARHL can be prevented in laboratory animals by certain interventions, such as caloric restriction and supplementation with antioxidants. In this review, we will focus on previous research concerning the role of the oxidative stress and mitochondrial dysfunction in the pathology of ARHL in both animal models and humans and introduce concepts that have recently emerged regarding the mechanisms of the development of ARHL.

Frequency tuning properties of ocular vestibular evoked myogenic potentials

Loud air-conducted sound or bone-conducted vibration produces vestibular-dependent electromyographic responses both in the cervical muscles (cervical vestibular evoked myogenic potentials) and in the extraocular muscles (ocular vestibular evoked myogenic potentials; oVEMPs). Although previous frequency tuning measurements of cervical vestibular evoked myogenic potentials have provided important information for a clinical application, those of oVEMPs have rarely been studied. We explored the frequency tuning properties of oVEMPs in 12 healthy participants. Our results indicate that the best frequencies of the oVEMPs to air-conducted sound and bone-conducted vibration are 500 and 250 Hz, respectively. The difference in the best frequencies between the two stimuli may originate from the difference in the end organs (saccule or utricle), preferentially activated by each stimulus.

Novel subtype of idiopathic bilateral vestibulopathy: bilateral absence of vestibular evoked myogenic potentials in the presence of normal caloric responses

To characterize clinical features of those patients who showed an absence of vestibular evoked myogenic potential (VEMP) responses in the presence of normal caloric responses bilaterally, we reviewed clinical records of 1,887 consecutive outpatients who complained of balance problems, and identified three patients, who showed absent VEMPs in the presence of normal caloric responses bilaterally with unknown causes. All three patients had episodes of recurrent vertigo without spontaneous, gaze-evoked, or positional nystagmus at the time of examination. They complained of oscillopsia while moving their body or head and showed positive Romberg’s signs. Drawing on these cases, we underscore the importance of examining the function of the inferior vestibular nerve system, even with no nystagmus and normal caloric findings, in patients complaining of dizziness or oscillopsia during locomotion.

Reactive Oxygen Species, Apoptosis, and Mitochondrial Dysfunction in Hearing Loss

Reactive oxygen species (ROS) production is involved in several apoptotic and necrotic cell death pathways in auditory tissues. These pathways are the major causes of most types of sensorineural hearing loss, including age-related hearing loss, hereditary hearing loss, ototoxic drug-induced hearing loss, and noise-induced hearing loss. ROS production can be triggered by dysfunctional mitochondrial oxidative phosphorylation and increases or decreases in ROS-related enzymes. Although apoptotic cell death pathways are mostly activated by ROS production, there are other pathways involved in hearing loss that do not depend on ROS production. Further studies of other pathways, such as endoplasmic reticulum stress and necrotic cell death, are required.

Noisy vestibular stimulation improves body balance in bilateral vestibulopathy

Objective: To examine the effect of an imperceptible level of galvanic vestibular stimulation (GVS), delivered as zero-mean current noise (noisy GVS), on postural performance in healthy subjects as well as in patients with bilateral peripheral vestibular dysfunction. Methods: White noise GVS with an amplitude ranging from 0 to 1,000 μA was applied in 21 healthy subjects and 11 patients with bilateral vestibular dysfunction. Two-legged stance tasks were performed with the eyes closed during a 60-second period, which consisted of a baseline period without stimulation and a stimulation period with GVS. We examined 3 parameters: the velocity, the envelopment area, and the root mean square (RMS) of the center of pressure. Results: White noise GVS improved all 3 parameters in 76% of healthy subjects. The amplitude of the optimal stimulus was 281 ± 40 μA, and it improved the velocity, area, and RMS by 18.4% ± 2%, 37.9% ± 3.5%, and 20.4% ± 2.2%, respectively (p < 0.01). The GVS improved all 3 parameters in 91% of patients. The amplitude of the optimal stimulus was 456 ± 82 μA, and it improved the velocity, area, and RMS by 29.4% ± 4.9%, 45.6% ± 4.7%, and 22% ± 3.3%, respectively (p < 0.01). Conclusions: Noisy GVS is effective in improving postural stability in healthy subjects as well as in patients with bilateral vestibular dysfunction. Classification of evidence: This study provides Class IV evidence that in patients with bilateral vestibular dysfunction, an imperceptible level of noisy GVS may improve postural stability.

Effect of vestibular dysfunction on the development of gross motor function in children with profound hearing loss.

Objective: To evaluate the function of the superior and inferior vestibular nerve systems in children with profound sensorineural hearing loss, and to assess the influence of dysfunction of each vestibular nerve system on the development of gross motor function. Study Design: Retrospective study. Setting: A tertiary referral center. Methods: Eighty-nine children (age range: 20–97 months) with profound sensorineural hearing loss who were due to undergo cochlear implant surgery were recruited. Function of the superior vestibular nerve system was evaluated by the damped rotation test and the caloric test, whereas functions of the inferior vestibular nerve systems were evaluated by the vestibular evoked myogenic potential (VEMP) test. Gross motor development was assessed using the age of acquisition of head control and independent walking. Results: Among the children able to complete the vestibular function tests, abnormalities were found in 20% (16 of 84 children) in the damped rotation test, 41% (31 of 75 children) in the caloric test and 42% (26 of 62 children) in the VEMP test. Children who showed abnormal responses in the vestibular function tests showed significantly delayed acquisition of head control (p < 0.05) and independent walking (p < 0.05) in comparison with children with normal responses. The children who showed abnormal responses in all 3 vestibular tests showed the greatest delay in acquisition of gross motor function in comparison with the other groups. Conclusions: Children with profound hearing loss tend to have dysfunction in the superior as well as the inferior vestibular nerve systems. Both the superior and inferior vestibular nerve systems are important for the development of gross motor function in children.

The diagnostic value of vestibular-evoked myogenic potential in patients with vestibular schwannoma

OBJECTIVE This study examined the diagnostic value of the vestibular-evoked myogenic potential (VEMP) in comparison with the caloric test in patients with vestibular schwannoma (VS). METHODS Data were retrospectively collected from 803 consecutive patients who visited our vertigo clinic and underwent vestibular tests. Amongst them, 78 patients were diagnosed as having untreated unilateral VS. VEMP was performed using click and short-tone burst stimulation. The caloric test was performed using ice water. The sensitivity and specificity of each test were evaluated. RESULTS Of the 78 patients with VS, 63 had abnormal VEMPs as well as abnormal caloric responses. Of the 725 patients without VS, 382 had normal VEMPs and 416 had normal caloric responses. The sensitivity and specificity of VEMP were 80.8% (95% CI: 72.0-89.5%) and 52.7% (95% CI: 49.1-56.3%), respectively; those of the caloric test were 80.8% (95% CI: 72.0-89.5%) and 57.4% (95% CI: 53.8-61.0%), respectively. CONCLUSIONS The sensitivity and specificity of VEMP and the caloric test showed no significant differences. SIGNIFICANCE In patients with VS, although the specificity of VEMP was not very high, its sensitivity was high and comparable to that of the caloric test.

Lesion site in idiopathic bilateral vestibulopathy: A galvanic vestibular-evoked myogenic potential study

Conclusion The result suggests that patients with idiopathic bilateral vestibulopathy may have nerve lesions when the inferior nerve system is affected, while the inferior vestibular nerve system may be spared. Objective To clarify the lesion site in idiopathic bilateral vestibulopathy, an acquired bilateral vestibulopathy of unknown cause. Material and methods Two 75-year-old males diagnosed with idiopathic bilateral vestibulopathy were enrolled. Both showed absent or highly decreased responses on the caloric test on both sides. They underwent vestibular-evoked myogenic potential (VEMP) testing by means of acoustical and electrical stimulation. As acoustic stimulation, 95 dB nHL clicks and short tone bursts (500 Hz) were presented, while 3 mA (1 ms) short-duration galvanic stimuli were presented as electrical stimulation. Responses were recorded on the sternocleidomastoid muscles. Results Both patients showed unilateral absence of VEMPs with both acoustic and short-duration galvanic stimuli.