Ebook Rapid interpretation of balance function tests: Part 2
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Ebook Rapid interpretation of balance function tests: Part 2
5Videonystagmography/ ElectronystagmographyOverview of Videonystagmography/ ElectronystagmographyVideonystagmography (VNG)/electronystagmography (ENG) Ebook Rapid interpretation of balance function tests: Part 2) are utilized to evaluate the integrity of both the peripheral and central vestibular systems. Commonly, the ocular motor studies described in the previous chapter are performed as part of the VNG/ENG. The ocular motor portion of the VNG/ENG provides the majority of the information regarding centra Ebook Rapid interpretation of balance function tests: Part 2l vestibular function. Most other portions of the test battery reveal information regarding the peripheral vestibular system. VNG/ ENG is the only meaEbook Rapid interpretation of balance function tests: Part 2
ns to assess vestibular function on one side independent of input from the opposite side. Therefore, it is an invaluable tool for identifying the side5Videonystagmography/ ElectronystagmographyOverview of Videonystagmography/ ElectronystagmographyVideonystagmography (VNG)/electronystagmography (ENG) Ebook Rapid interpretation of balance function tests: Part 2thi of the eyes to record the corneo-retinal potentials (ENG) or eye movement video monitoring using infrared cameras (VNG) to assess the vestibular ocular5354 RAPID INTERPRETATION OF BALANCE FUNCTION TESTSFigure 5-1. VNG/ENG provides information regarding peripheral and central vestibular integrity Ebook Rapid interpretation of balance function tests: Part 2.reflex (VOR) during several subtests.2-5 The information obtained from these subtestscan provide information regarding symptom causality and physioloEbook Rapid interpretation of balance function tests: Part 2
gic compensation status.Components of VNG/ENGSpontaneous Nystagmus TestSpontaneous nystagmus can result from central or peripheral vestibular patholog5Videonystagmography/ ElectronystagmographyOverview of Videonystagmography/ ElectronystagmographyVideonystagmography (VNG)/electronystagmography (ENG) Ebook Rapid interpretation of balance function tests: Part 2 nystagmus of central etiology results from more complex neural processes.Test AdministrationThe patient is in a seated position with the eyes opened, while the presence or absence of nystagmus is determined. Vision needs to be denied because a nystagmus of a peripheral etiology will be suppressed w Ebook Rapid interpretation of balance function tests: Part 2ith visual fixation. With ENG recordings, spontane-VIDEONYSTAGMOGRAPHY/ELECTRONYSTAGMOGRAPHY 55OUS nystagmus testing is performed with eyes closed. WiEbook Rapid interpretation of balance function tests: Part 2
th VNG recordings, spontaneous nystagmus testing is performed with eyes opened and vision removed by opaque goggles. If spontaneous nystagmus is obser5Videonystagmography/ ElectronystagmographyOverview of Videonystagmography/ ElectronystagmographyVideonystagmography (VNG)/electronystagmography (ENG) Ebook Rapid interpretation of balance function tests: Part 2ixation suppression. When spontaneous nystagmus does not suppress or is enhanced with visual fixation, then a central etiology may be suggested.Test InterpretationSpontaneous nystagmus is always clinically significant regardless of the degree. When the nystagmus is horizontal/torsional, then a perip Ebook Rapid interpretation of balance function tests: Part 2heral vestibular etiology is more commonly suggested. The direction of the fast phase of the nystagmus will provide insight into which side is more exEbook Rapid interpretation of balance function tests: Part 2
cited or firing at a stronger rate. For example, right-beating spontaneous nystagmus suggests that the right peripheral vestibular system is being mor5Videonystagmography/ ElectronystagmographyOverview of Videonystagmography/ ElectronystagmographyVideonystagmography (VNG)/electronystagmography (ENG) Ebook Rapid interpretation of balance function tests: Part 2htbeating spontaneous nystagmus is the only abnormal finding, one could report that there is either a left paretic or right irritative lesion, but further lateralization of the abnormality is not possible. In this scenario, there maybe clinical supporting evidence, such as asymmetric hearing loss an Ebook Rapid interpretation of balance function tests: Part 2d/or tinnitus that would suggest that one is the more likely abnormal side than the other.When there is no spontaneous nystagmus observed, it does notEbook Rapid interpretation of balance function tests: Part 2
necessarily mean that the peripheral vestibular mechanisms on both sides are normal and symmetric. Because of the process of physiologic compensation5Videonystagmography/ ElectronystagmographyOverview of Videonystagmography/ ElectronystagmographyVideonystagmography (VNG)/electronystagmography (ENG) Ebook Rapid interpretation of balance function tests: Part 2s results in the improvement of the patient's subjective vertiginous symptoms and the cessation of the spontaneous nystagmus. This process of physiologic compensation can occur in less than one week,4 but is often affected by the patient's age, level of activity, and the use56 RAPID INTERPRETATION O Ebook Rapid interpretation of balance function tests: Part 2F BALANCE FUNCTION TESTSTable 5-1. Spontaneous Nystagmus—Quick Tips for Rapid Interpretation•Spontaneous nystagmus is always clinically significant.•CEbook Rapid interpretation of balance function tests: Part 2
an only be observed in the absence of vision because visual fixation will suppress spontaneous nystagmus that results from a peripheral vestibular eti5Videonystagmography/ ElectronystagmographyOverview of Videonystagmography/ ElectronystagmographyVideonystagmography (VNG)/electronystagmography (ENG) Ebook Rapid interpretation of balance function tests: Part 2way from the paretic side.•When it is the result of an irritative lesion, then the nystagmus will beat toward the irritated side.•When spontaneous nystagmus is present, then physiologic compensation has not occurred.•Vertical spontaneous nystagmus is associated with central nervous system etiologies Ebook Rapid interpretation of balance function tests: Part 2.of vestibular suppressants, all of which can delay or preclude the process of compensation.6'8When spontaneous nystagmus is purely vertical, either dEbook Rapid interpretation of balance function tests: Part 2
own-beating or up-beating, then a central nervous system etiology is more likely. Possible causes of down-beating nystagmus include cerebellar abnorma5Videonystagmography/ ElectronystagmographyOverview of Videonystagmography/ ElectronystagmographyVideonystagmography (VNG)/electronystagmography (ENG) Ebook Rapid interpretation of balance function tests: Part 2em or cerebellar etiologies and multiple sclerosis. Any vertical nystagmus can be drug-induced (eg, alcohol, barbiturates, antiseizure medications), thus careful medication case history information is imperative (Table 5-1 ).4'9Head Shake and Head Thrust TestsThe head shake and the head thrust tests Ebook Rapid interpretation of balance function tests: Part 2 are both dynamic tests that entail stimulation of the peripheral vestibular mechanisms, specifically the semicircular canals, by actively moving theEbook Rapid interpretation of balance function tests: Part 2
head and monitoring the VOR. The tests aim at identifying asymme-VIDEONYSTAGMOGRAPHY/ELECTRONYSTAGMOGRAPHY 57tries in the peripheral vestibular system5Videonystagmography/ ElectronystagmographyOverview of Videonystagmography/ ElectronystagmographyVideonystagmography (VNG)/electronystagmography (ENG)5Videonystagmography/ ElectronystagmographyOverview of Videonystagmography/ ElectronystagmographyVideonystagmography (VNG)/electronystagmography (ENG)Gọi ngay
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