Research advances on mechanism and lesion location of vertical nystagmus / 临床耳鼻咽喉头颈外科杂志

Summary@#Vertical nystagmus is a vertical nystagmus caused by structural abnormalities and/or dysfunction of the central vestibular system and observed in situ in the center of the eyeball. There are two kinds of nystagmus （UBN） and downbeat nystagmus （DBN） according to the direction of nystagmus. The diagnosis of UBN is mainly made by naked eye or electronystagmography/viewer. It is a common neuro-ophthalmologic sign in the field of vestibular medicine. In this paper, the mechanism of vertical nystagmus formation and the location of lesions were briefly introduced, in order to provide help for the diagnosis and treatment of Vertigo.

Research advances on mechanism and lesion location of vertical nystagmus / 临床耳鼻咽喉头颈外科杂志

Vertical nystagmus is a vertical nystagmus caused by structural abnormalities and/or dysfunction of the central vestibular system and observed in situ in the center of the eyeball. There are two kinds of nystagmus （UBN） and downbeat nystagmus （DBN） according to the direction of nystagmus. The diagnosis of UBN is mainly made by naked eye or electronystagmography/viewer. It is a common neuro-ophthalmologic sign in the field of vestibular medicine. In this paper, the mechanism of vertical nystagmus formation and the location of lesions were briefly introduced, in order to provide help for the diagnosis and treatment of Vertigo.

Changes of the Video Head Impulse Test Gains by the Directions of Head Rotation at Different Target Distances and Rotation Speeds / 대한이비인후과학회지

BACKGROUND AND OBJECTIVES: The conventional instrument for video head impulse test (vHIT) records the movement of the right eye only. The aim of this study was to evaluate the changes in the gain of vHIT results qdue to different directions of head rotation directons at different target distances and rotation speeds. SUBJECTS AND METHOD: Horizontal head impulse was recorded by vHIT in 20 normal subjects. vestibulo-ocular reflex (VOR) gains to the right and left directions were compared at different test conditions. Two different impulses with low (50-150 deg/sec) and high (200-300 deg/sec) peak-head-velocities were tested and the subjects were also instructed to fixate a laser dot on a screen at different distances of 60, 100, and 200 cm. Eye movements were recorded on the right eye. RESULTS: Regardless of the target distances and peak-head-velocities, the VOR gains to the rightward head rotation were significantly greater than those to the leftward head rotation. In more than 85% of normal subjects, vHIT gain to the rightward head rotation was greater than that to the leftward head rotation. Mean gain asymmetries were 2.16-3.33% and the mean interaural vHIT gain differences were 0.04-0.07. CONCLUSION: Regardless of the target distances and peak-head-velocities, the VOR gains to the rightward head rotation were significantly greater than those to the leftward head rotation. Directional asymmetry of VOR gain should be considered when interpreting vHIT results in patients with vestibular disorders.

Spontaneous Recovery of Vestibulo-Ocular Reflex Gain after Bilateral Complete Vestibular Loss Following Head Injury / 대한평형의학회지

Dizziness is a frequent complication of head injury and objective evidence of vestibular dysfunction in the dizzy patient following head injury has been reported in literatures. However, there is no report about bilateral spontaneous recovery of caloric response after complete loss of bilateral vestibular function following head injury. A 27-year-old male patient who presented with continuous dizziness and disequilibrium following head injury was diagnosed as diffuse axonal injury after brain magnetic resonance image and bilateral complete loss of vestibular function after caloric and rotary chair test. He showed gradual improvement of dizziness, vestibulo-ocular reflex gain and left caloric response at 2 months after vestibular exercise. After another 4 months, his caloric function was fully recovered, and dizziness disappeared at 16 months after the onset of dizziness. We present this case with reviews of previous literatures about dizziness following head injury and diffuse axonal injury.

Effects of Repetitive Multiaxial 3-dimensional Rotation Training on Vestibulo-ocular Reflex / 대한평형의학회지

BACKGROUND AND OBJECTIVES: The parameters of vestibulo-ocular reflex (VOR) are believed to indicate the quantitative value of vestibular function and the differences in them are related to the susceptibility of motion sickness. The purpose of this study was to investigate the effects of repetitive multiaxial 3-dimensional rotation training on VOR parameters. MATERIALS AND METHODS: Fifteen healthy volunteers were randomly assigned to 3 different groups according to the mode of exercise training. Aerotrim exercise was done as a method of repetitive multiaxial 3-dimensional rotation training. The changes in VOR parameters after 9 weeks of exercise training in Aerotrim training group were compared with that of other groups. RESULTS: While the values of VOR gain in Aerotrim training group after 9 weeks of exercise training were significantly lower than baseline values at rotation frequencies of 0.01, 0.04, 0.08, 0.16, and 0.32 Hz, values of VOR gain in other groups showed no difference between before and after exercise training. In all groups, there were no significant differences in VOR phase and symmetry values between before and after exercise training. CONCLUSION: This study showed that VOR parameters changed after 9 weeks of repetitive multiaxial 3-dimensional rotation training, and vestibular habituation might eventually occur. Since vestibular habituation is known to contribute to mitigating the frequency and the degree of motion sickness, we suggest that repetitive multiaxial 3-dimensional rotation training can be used as the countermeasure for student pilots or astronauts, who are often exposed to unusual motion and positional status in actual 3-dimensional space.

Perverted Head Shaking Nystagmus due to Cerebellar Lesions: Possible Mechanisms

BACKGROUND AND OBJECTIVES: Perverted head-shaking nystagmus (HSN) refers to nystagmus that develops in the plane other than that being stimulated by head oscillation, i.e., downbeat or upbeat HSN after head oscillation in the yaw plane. However, the mechanism of perverted HSN is unknown. To elucidate the mechanism of perverted HSN by measuring tilt suppression of the vestibule-ocular reflex (VOR). MATERIALS AND METHOD: Twenty two consecutive patients with perverted HSN from cerebellar lesions (13 circumscribed and 9 diffuse) and 50 normal volunteers underwent recording of spontaneous, head-shaking and positional nystagmus, smooth pursuit, saccades, and the VOR. Tilt suppression method was to pitch patients' head forward further at the end of the step rotation stimuli. RESULTS: HSN was pure downbeat in nine and mixed horizontal-downbeat in 13 patients. The mean VOR time constants did not differ between normal controls and patients. However, tilt suppression of the post-rotatory nystagmus was impaired in the patients (p<0.01). Downbeating (n=12) and central positional nystagmus (n=12) were frequently accompanied findings. CONCLUSION: Uvulonodular dysfunction was frequently observed in patients with perverted HSN from cerebellar lesions. Uvulonodulus may be involved in the spatial organization of the velocity storage mechanism and uvulonodular dysfunction may be responsible for developing perverted HSN in cerebellar lesions.

Perverted Head Shaking Nystagmus due to Cerebellar Lesions: Possible Mechanisms

BACKGROUND AND OBJECTIVES: Perverted head-shaking nystagmus (HSN) refers to nystagmus that develops in the plane other than that being stimulated by head oscillation, i.e., downbeat or upbeat HSN after head oscillation in the yaw plane. However, the mechanism of perverted HSN is unknown. To elucidate the mechanism of perverted HSN by measuring tilt suppression of the vestibule-ocular reflex (VOR). MATERIALS AND METHOD: Twenty two consecutive patients with perverted HSN from cerebellar lesions (13 circumscribed and 9 diffuse) and 50 normal volunteers underwent recording of spontaneous, head-shaking and positional nystagmus, smooth pursuit, saccades, and the VOR. Tilt suppression method was to pitch patients' head forward further at the end of the step rotation stimuli. RESULTS: HSN was pure downbeat in nine and mixed horizontal-downbeat in 13 patients. The mean VOR time constants did not differ between normal controls and patients. However, tilt suppression of the post-rotatory nystagmus was impaired in the patients (p<0.01). Downbeating (n=12) and central positional nystagmus (n=12) were frequently accompanied findings. CONCLUSION: Uvulonodular dysfunction was frequently observed in patients with perverted HSN from cerebellar lesions. Uvulonodulus may be involved in the spatial organization of the velocity storage mechanism and uvulonodular dysfunction may be responsible for developing perverted HSN in cerebellar lesions.

Comparison of Vestibule-ocular Reflex of Eccentric Rotation with Centric Rotation in Normal Subjects

BACKGROUND AND OBJECTIVES:Conventional vestibular rotation testing with the head centered on the axis stimulates the semicircular canals evoking compensatory eye movements. By placing subjects off from the axis of rotation, the otolithic organ may also be simultaneously stimulated by additional linear acceleration forces. In the present study, we compared the rotation with subjects placed on axis to those placed in an eccentric position. MATERIALS AND METHOD:In the eccentric rotation, the head of subject was facing outward and placed eccentrically for 33cm on naso-occipital axis. Slow harmonic acceleration test and velocity step test were performed. RESULTS:The sinusoidal eccentric rotation at 0.32, 0.64 Hz produced a significantly higher vestibulo-ocular reflex gain than did on axis rotation. In velocity step test, initial slow component velocity was significantly higher in eccentric rotation than in centric rotation. CONCLUSION:These finding suggest that the gain enhancement due to eccentric rotation is a result of tangentiallinear acceleration, probably sensed by the otolithic organ. This study raises the possibility of using eccentric rotation for the diagnosis of the patients with otolithic dysfunction.