-
New Views of the Translational Vestibulo-ocular Reflex in Healthy Human Subjects and in Patients with Neurological Disease who Fall
-
R John Leigh, Ke Liao, Jae Il Kim
-
Res Vestib Sci. 2010;9(3):100-107.
-
-
-
 Abstract
 PDF
- Background and Objectives: The vestibulo-ocular reflexes (VOR) act a short latency to optimize vision during locomotion. The angular VOR (aVOR) has been widely studied in human subjects and preserves clear, stable vision during rotational head perturbations by generating eye movements that hold the line of sight on the target of interest. Less is known about the properties of the linear or translational VOR (tVOR), mainly due to technical difficulties posed by testing head or body translations. Geometric considerations indicate that different properties should be expected of tVOR, which can only provide stable vision of objects lying in one depth plane.
Materials and Methods: We studied the human tVOR using a moving platform to translate normal human subjects vertically at frequencies similar to those occurring during locomotion. We found that, whereas aVOR is concerned with holding retinal images fairly stable to optimize clear vision, tVOR seems best suited to minimize relative motion of retinal images belonging to objects lying in different depth planes-and thereby to optimize motion parallax information. We also investigated whether the tVOR functioned abnormally in patients with neurological disorders causing falls-progressive supranuclear palsy (PSP) and cerebellar ataxia.
Results: Both groups of patients showed impaired ability to modulate their tVOR during viewing of near targets; in PSP this might be attributed to failure of convergence, but cerebellar patients failed to modulate tVOR at near despite intact convergence.
Conclusion: In both disorders, an impaired ability to adjust tVOR for viewing distance points to central disturbance of otolithic vestibular reflexes, which may also contribute to postural instability.
-
Hyperventilation Induced Nystagmus in Patient with Vestibular Schwannoma : A Case Report
-
Yoon Jeong Chang, Geun Ho Lee, Chang Min Lee, Young Mok Song, Chung Ku Rhee, Jae Il Kim
-
J Korean Bal Soc. 2004;3(1):177-179.
-
-
-
Abstract
PDF
- When doctors evaluate the complaints of dizziness, they often perform a series of clinical tests to look for the
evidence of a vestibular dysfunction. A useful procedure is to ask the patient to take deep breaths and observe the gaze
behind Frenzel goggles. If hyperventilation-induced nystagmus(HIN) is detected, it is the evidence for an underlying
vestibular imbalance. The authors evaluated nystagmus with electronystagmography after hyperventilation for 50
seconds. Brain imaging was performed to search the responsible lesion for dizziness. Brain MRI revealed a brain tumor
suggesting vestibular schwannoma in the left cerebellopontine angle. After hyperventilation, dizziness and the right
beating horizontal nystagmus with Alexander law could be detected. By precisely measuring the HIN, we determined
that inputs arising from the horizontal semicircular canal were mainly responsible. The contralaterality of the direction
of the horizontal component of the nystagmus was detected. We suggest that clinicians should routinely check the
nystagmus after hyperventilation, when they evaluate patients complaining of dizziness.
|
KBS
