Frequency analyses of posturography using logarithmic translation.

Background: Power-spectral analysis of the centre of pressure (CoP) frequencies of posturography provides exponentially approximated distributions, whereas logarithmic translation enables linear approximation.Objectives: Frequency analyses were adopted for posturography of healthy subjects and patients with spinocerebellar degeneration (SCD) using logarithmic translation to determine its clinical usefulness for managing the elderly and patients with disequilibrium.Material and methods: We included 172 healthy subjects and 47 SCD patients. Posturography was performed with the eyes fixated and closed, with and without foam rubber. The power-spectral data of the CoP were obtained with the maximum entropy method. Power-spectral data were logarithmically translated for quantitative evaluation.Results: For teenagers, high-frequency fluctuations were dominant and attributable to proprioceptive compensation due to immature postural control. In elderly populations, the increased frequency in the lateral direction was characterised by three peaks indicating postural disturbances attributed to three sensory inputs. The disappearance of one peak in the anteroposterior fluctuation indicates a decrease in vestibular contribution. The foam rubber and the closed-eye condition enhanced fluctuations in two peaks. There were differences in power-spectral distributions of two peaks between the healthy subjects and SCD patients.Conclusions: Logarithmic power-spectral data distribution could provide an age- and disease-specific novel and visually-comprehensible parameter.

Vestibular Dysfunction in Patients With Superficial Siderosis of the Central Nervous System.

OBJECTIVE: To describe the vestibular function in patients with superficial siderosis of the central nervous system (SSCN). STUDY DESIGN: Retrospective analysis. SETTING: Tertiary referral center. PATIENTS: Ten consecutive patients with SSCN. This study is the largest case series of SSCN in which detailed neuro-otological findings, including electronystagmography recording, video head impulse test (vHIT), and posturography, were described. INTERVENTIONS: Audiological and neuro-otological examinations, including pure-tone audiometry, distortion product otoacoustic emissions, speech audiometry, auditory brainstem responses, electronystagmography recording, vHIT, and posturography. MAIN OUTCOME MEASURES: Pure-tone average, DP level, maximum speech discrimination score, interpeak latency between auditory brainstem responses waves I and V, eye tracking test, examination of optokinetic nystagmus, caloric response, visual suppression, vestibulo-ocular reflex gains, total center of pressure path length, and Romberg's ratio. RESULTS: Audiological examinations suggested that the sensorineural hearing loss was of a cochlear etiology in 3 ears, a retrocochlear etiology in 11 ears, and a combined cochlear and retrocochlear etiology in 6 ears. Neuro-otological examinations revealed that eight out of nine patients had cerebellar disorders, while all patients also had peripheral vestibular dysfunction. CONCLUSION: In addition to cerebellar disorders, SSCN patients suffer from severe peripheral vestibular dysfunction, which can exacerbate the patient's imbalance. When otolaryngologists encounter patients with distinctly progressive sensorineural hearing loss and imbalance, they should include SSCN in the differential diagnosis and perform neuro-otological examinations, including an electronystagmography recording and vHIT and brain magnetic resonance imaging.

Determination of the time course of caloric nystagmus in patients with spinocerebellar degeneration using caloric step stimulus procedure.

CONCLUSIONS: The step stimulus procedure can provide information on the time course of the vestibulo-ocular reflex. Spinocerebellar degeneration and aging seem to shorten the time constant of the onset of the vestibulo-ocular reflex, causing a rapid rise up. Failure of the central processing of velocity storage might contribute to this rapid rise up. OBJECTIVES: The aim of this study is to evaluate the time course characteristics of the vestibulo-ocular reflex in patients with spinocerebellar degeneration. METHODS: Ten patients (20 ears) and 22 healthy subjects (30 ears) underwent caloric test using the step stimulus procedure. We evaluated the time course of caloric VOR and calculated the parameters of the time constant of an activation and adaptation response. We compared between the control and SCD groups to elucidate the time course characteristics of caloric VOR in patients with SCD. RESULTS: Spinocerebellar degeneration seems to shorten the time constant of the activation response by caloric irrigation with 20 °C, 7l/min air. However, aging also possibly contributes to this shortening. No change was observed in the time constant of the adaptation response.

Nystagmus at the Onset of Vertiginous Attack in Ménière's Disease.

OBJECTIVE: To clarify the direction and characteristics of nystagmus at the onset of a vertiginous attack in Ménière's disease. PATIENTS: Two patients with Ménière's disease, whose nystagmus at the onset of a vertiginous attack was recorded using electronystagmography. INTERVENTIONS: Diagnostic. MAIN OUTCOME MEASURES: Electronystagmographic recordings of nystagmus. RESULTS: In both patients, nystagmus was directed toward the affected side over the entire course of the vertiginous attack. One patient experienced a severe sensation of vertigo and exhibited strong nystagmus from the onset of the attack. The other patient reported a mild sensation of vertigo, which was accompanied by intermittent nystagmus. CONCLUSIONS: Vertiginous attacks in Ménière's disease are accompanied by irritative nystagmus. The intensity and characteristics (e.g., continuous or intermittent expression) of the nystagmus may be associated with pathophysiological severity.