Compensation of the Postural Instability in Patients with Acute Unilateral Vestibular Neuritis: The Usefulness of Computerized Dynamic Posturography as an Objective Indicator / 대한이비인후과학회지

BACKGROUND AND OBJECTIVES: The aim of this study was to evaluate the usefulness of computerized dynamic posturography (CDP) in patients with acute vestibular neuritis (AVN) by identifying the recovery period of Sensory Organization Test (SOT) and comparing the result of SOT with those of the vestibulo-ocular reflex (VOR) tests and subjective symptoms. SUBJECTS AND METHOD: A prospective study was conducted on 41 patients who were diagnosed with AVN. The SOT was measured daily until the equilibrium composite score recovered the normal value. A survey, composing of questionnaires on Visual Analogue Scale (VAS), Dizziness Handicap Inventory (DHI), motion sensitive quotient (MSQ) and Activities-Specific Balance Confidence Scale (ABC), was conducted on the patient's initial visit and on the day the normal value of SOT was recovered. Videonystagmography and the caloric test were also performed, and the results were compared with those of the SOT. RESULTS: The mean duration from the onset of vertigo to the recovery of SOT scores was 3.7±2.9 days (median 3.0 days) and that from the onset of vertigo to the disappearance of spontaneous nystagmus was 17.1±27.2 days (median 6.0 days). The scores of 4 questionnaires (VAS, DHI, MSQ, and ABC) were significantly different between the initial day and the day of recovery to the normal value of SOT (p<0.001). However, the velocity of spontaneous nystagmus on the initial visit and the degree of canal paresis from the caloric test showed no significant correlations to recovery duration from the onset of vertigo to the normalization of SOT score. CONCLUSION: The recovery duration of vestibulospinal reflex (VSR) is much shorter than that of VOR in patients with AVN. The recovery of subjective symptoms showed close correlation with the recovery of VSR, but the results of VSR was not correlated with that of VOR. Therefore, CDP could be a very useful test for monitoring the resolution of subjective symptoms in patients with AVN.

Clinical Significance of Perverted Head-Shaking Nystagmus / 대한평형의학회지

OBJECTIVES: We investigated clinical significance of head shaking nystagmus (HSN) and perverted HSN (pHSN) in patients with peripheral and central vestibular disorders. METHODS: We reviewed medical records of 822 consecutive subjects who were referred to a dizziness clinic. We performed neurologic examination including video-oculography in darkness for 60 seconds before, during and for 100 seconds after head-shaking. HSN was considered to develop when post-head-shaking nystagmus last at least 5 beats with latency from end of head-shaking of no more than 5 seconds, and a velocity at least 3°/sec. RESULTS: In control group (n=45), there were observed spontaneous nystagmus (SN) in 2.2%, HSN in 17.8%, pHSN in 6.7%. In patients with peripheral vestibular disorder group (n=397), there were observed SN in 14.1%, HSN in 40.6%, pHSN in 9.8%. In patients with central vestibular disorder group (n=217), there were observed SN in 17.5%, HSN in 24.0%, pHSN in 13.4%. In unspecified dizziness group (n=208), there were observed SN in 1.9%, HSN in 13.0%, pHSN in 1.9%. pHSN was frequently observed in central vestibular disorders such as stroke, vestibular migraine, cerebellar ataxia, and vertebro-basilar insufficiency. However, pHSN was also observed at higher rate than expected in peripheral vestibular disorders including benign paroxysmal positional vertigo especially involving vertical canals, Meniere disease and even in unilateral vestibulopathy. CONCLUSIONS: Our results show that perverted HSN in dizzy populations was frequently observed not only in cases of central vestibular disorders but also in peripheral disorders. Perverted HSN can develop by any conditions that cause difference in vestibular velocity storage in vertical component of vestibular-ocular reflex.

Neurovestibular Compensation following Ototoxic Lesion and Labyrinthectomy

Abstract Introduction Unilateral labyrinthectomy and intra-tympanic gentamycin have been employed in the treatment of Ménière's disease, but the efficacy of these techniques has not been well established. Objective The objective of this study is to measure the time course of recovery from a unilateral labyrinthectomy either after ipsilateral topical treatment with gentamicin to the inner ear or without the previous insult. Methods Twenty-nine adult Mongolian gerbils were randomized into two experimental groups. Group 1 (n=17) received a right ear gentamicin drug-induced lesion by unilateral labyrinthectomy (UL). Group 2 (n=12) only received a right unilateral labyrinthectomy lesion. We measured the horizontal vestibulo-ocular responses in gerbils before and after the lesion. The gerbils received an angular acceleration stimulus and their eye movements were recorded. Results The gentamicin lesion resulted in a quicker recovery. Experimental groups underwent a similar time course of recovery. Statistical analysis showed no significant difference between the two groups. Both groups displayed adaptation to the lesion by day 21, but long-term compensation did not completely revert to the original pre-lesion state. Conclusions In a lesion requiring both static and dynamic compensation as in UL, the need for a static compensation may alter pre-existing compensation from a previous dynamic insult and require a new compensation. A previous lesion and adaptation is not preserved for a second lesion and the subject has to re-compensate. Therefore, surgical treatment in Meniere's disease such as UL can be considered without prior gentamicin treatment. Static and dynamic compensations do not appear to be as independent as previous studies have suggested.

Effects of Flight Training on Vestibuloocular Reflex in Student-pilots

The aim of this study was to investigate the effect of flight training on vestibuloocular reflex (VOR) induced by rotational chair test in student-pilots. The study group was divided into followings; control, prepilot (student-pilots before flight training), and student-pilot (after training). Gain, phase and symmetry of eye movement induced by sinusoidal harmonic acceleration with frequencies of 0.01, 0.02, 0.04, 0.08, 0.16, 0.32 Hz. Gain and phase did not show any significant differences between control and student-pilots before flight training in all frequencies. But there were significant gain differences between control and student-pilots after flight training in 0.01, 0.04, 0.08 frequencies. And phase showed significant differences between before and after flight training in student-pilots in 0.01, 0.04 Hz. These results suggest that the flight training would be attributable to modulate the vestibular function in the student-pilots.

Electrical stimulation can facilitate vestibular compensation following unilateral labyrinthectomy in rats

To investigate the effects of electrical stimulation on vestibular compensation, which is the recovery of vestibular symptoms following unilateral labyrinthectomy (UL), intermittent electrical stimulation was applied to the injured vestibular portion in Sprague-Dawley rats. Vestibuloocular and vestibulospinal reflexes, electrical activity and expression of c-Fos protein in medial vestibular nuclei (MVN) were measured with time following UL. Spontaneous nystagmus occurred with frequency of 2.9+/-0.2 beats/sec at 2 hours after UL and disappeared after 72 hours. Electrical stimulation decreased the frequency of nystagmus significantly till 24 hours after UL. Roll head deviation was 107+/-9.7degree at 2 hours after UL and the deviation was maintained till 72 hours, but electrical stimulation decreased the deviation significantly 6 hours after UL. Resting activity of type I neurons in ipsilateral MVN to the injured vestibular side decreased significantly compared with control at 6 and 24 hours after UL, but the activity of type I neurons was recovered to control level by electrical stimulation at 24 hours after UL. Gain of type I neurons induced by sinusoidal rotation of 0.1 Hz decreased significantly till 24 hours after UL, but electrical stimulation restored the activity at 24 hours. The gain of type II neurons decreased significantly at 6 hours after UL, but electrical stimulation restored the activity. Expression of c-Fos protein was asymmetric between bilateral MVN till 24 hours after UL, but the asymmetry disappeared by electrical stimulation 6 hours after UL. These results suggest that electrical stimulation to the injured vestibular portion facilitates vestibular compensation following UL by restoration of symmetry of neuronal activity between bilateral vestibular nuclei resulting from increased activity in ipsilateral vestibular nuclei to the injured side.

Alterations of Vestibuloocular Reflex and Heart Rate Variability by Sinusoidal Rotation in Adults

BACKGROUND: The nature of the interactions between the vestibular and autonomic systems is complex and has not been fully defined. The vestibuloocular reflex induced by sinusoidal rotation and the activity of the autonomic nerves in the heart were measured to investigate the interactions between the vestibular system and the autonomic nervous system in healthy adults. METHODS: Eye movements induced by sinusoidal rotation of the whole body or optokinetic stimulation at 0.04 Hz were analyzed in regards to their gain, phase, and symmetry. EKG was measured during vestibular stimulation and analyzed in heart rate variabilities including mean R-R interval, standard deviation (SD) and coefficient of variance (CV) of R-R interval, and power spectrum of the low frequency region (LF) and high fre-quency region (HF). RESULTS: The gain of eye movement was 0.65 degree +/-0.03 by rotatory stimulation and 0.70 degree +/-0 . 0 2 by optokinetic stimulation. The gain of visual suppression was 0.08 degree +/-0.02, which was a significant decrease com-pared with the rotatory stimulation, and visual enhancement increased the gain significantly, 0.84 degree +/-0.04 (p<0.01). In the R-R interval, the resting condition (control) was 0.82 degree +/-0.03 sec. Rotatory and optokinetic stimulations did not show any significant differences compared with the control, however, visual suppression showed a significant increase and visual enhancement showed a significant decrease (p<0.01). CV was 0.06 degree +/-0.02 in the control and visual enhancement increased significantly (p<0.05). In LF/HF the control was 1.40 degree +/-0.23, which was not different from the rotatory or optokinetic stimulation. However, visual suppression decreased the LF/HF significantly and visual enhancement increased the LF/HF significantly compared with the control (p<0.01). CONCLUSIONS: These results suggest that the degree of gain corresponds with LF/HF and that increased gain in visual enhancement is related to the activity of the sympathetic nerves.