Objectives Suppression head impulse paradigm (SHIMP) in video head impulse test is now newly used to test vestibular function. The aim of this study was to analyze normative values of SHIMP for healthy Korean subjects in each decade of life.
Methods SHIMP and HIMP responses were measured with the video head impulse test in 70 healthy subjects. Vestibulo-ocular reflex gain and anticompensatory saccade were analyzed and compared at each decade of life.
Results All subjects produced anticompensatory saccades in SHIMP. Gain values did not vary significantly with age. Gain values in SHIMP were lower than gain values in HIMP. The gain values of rightward impulse were higher than the gain values of leftward impulse.
Conclusions Gain values and anticompensatory saccades in SHIMP were consistently equal in each decade of life. Normative values of SHIMP seems largely unaffected by aging.
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Normalization of the Suppression Head Impulse Test (SHIMP) and its correlation with the Head Impulse Test (HIMP) in healthy adults Suheda Baran, Gulce Kirazli, Pelin Pistav Akmese, Nese Celebisoy, Tayfun Kirazli Journal of Vestibular Research.2024; : 1. CrossRef
The anterior cerebellar vermis has been known to act in coordination of gait and postural adjustment of the trunk and legs. However, oculomotor abnormalities in an isolated anterior vermian lesion have not been described in the literature. A 59-year-old man presented with acute non-rotatory dizziness and disequilibrium. Neuro-ophthalmologic examination found impaired smooth pursuit and hypometric saccades in the contralesional direction, and disconjugate ipsiversive ocular torsion, but without spontaneous or gaze-evoked nystagmus. Imaging study showed an infarction restricted to the rostral end of right cerebellar vermis involving the lingual and central lobules. The anterior cerebellar vermis participates in the maintenance of axial posture and gait, and also in the control of ocular motor and vestibular systems.
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Vestibulo-ocular reflex is a reflex eye movement that stabilizes images on the retina during head movement by producing an eye movement in the direction opposite to head movement, thus preserving the image on the center of the visual field. The peripheral vestibular receptors which detect head movement transduce the physical stimulus into electrical signals and send the signals to the vestibular nuclei in the beainstem via the vestibular nerve. From these nuclei, fibers project to the ocular motor nuclei which contain motoneurons that drive extraocular muscle activity. Characteristics of anatomy and physiology of the vestibulo-ocular system, stimulation of the vestibular system, measurement and analysis of eye movement, and clinical significance of the vestibule-ocular reflex were described as followings.
Background and Objectives : Convergence-retraction oscillations are rhythmic or arrhythmic jerks of dysjunctive eye movements associated with backward displacement of the eyeballs during the convergence phase. Oscillations in convergence-retraction oscillations have been proposed to be consisted of opposed adducting saccades immediately followed by slow abducting glissades without latency. However, dynamic characteristics of convergence oscillations accompanying retraction have not been studied, and pathomechanism of these eye movements remains to be elucidated. This study was to get insights on the pathomechanisms of convergence-retraction oscillations by using 3-dimensional recording of eye movements. In particular, we intended to clarify whether the nystagmus originates from instability of vergence eye movement or of saccades.
Materials and Method : Seven consecutive patients with convergence-retraction oscillations were recruited. All the patients received full neurological and neuro-ophthalmological evaluation by the senior author. Some of the patients underwent 3-dimensional recordings of convergence-retraction oscillations with video-oculography or magnetic search coil technique.
Results : Wave forms of convergence-retraction oscillations were varied. The onset of convergent eye movements was either synchronous or asynchronous between both eyes. The initial directions of eye movement was same (conjugate) or opposite (disjunctive). In some, vergence eye movements occurred only in one eye (unilateral). Convergence phase of one eye was commonly consisted of multiple steps while the other eye attained final position with a single step. The following divergent eye movements commonly overshoot the orbital midposition and were followed by correcting convergent eye movements. The velocity-amplitude relationship of convergent eye movements, which was analyzed in typical pairs of vergence oscillations, did not differ between both eyes. Divergent eye movements are slower than convergent eye movements. The both convergent and divergent eye movements were slower than the microsaccades of similar amplitudes.
Conclusion : Quantitative analyses of convergence-retraction oscillations revealed various patterns of wave forms. The amplitude-velocity relationships of the disjunctive eye movements suggest that the slowed saccades may be due to co-contraction of the agonist and antagonist, or due to enhanced vergence eye movements by the accompanying saccades.