Term
| What are the five major Dx testing procedures outlined in our handout? |
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Definition
| Caloric testing (electronystagmography), Rotational Testing, Posturography, Oculomotor testing, positional testing. |
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Term
| Why does caloric testing reproduce Sx? |
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Definition
| Because of the thermal gradient across the horizontal canal. There is a differential gradient between the fluid and ear temperature. The fluid in the ear will move from warm -> cold if H20 is cold, or cold -> warm if H20 is warm. |
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Term
| Describe the caloric testing procedure. |
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Definition
| Pt positioned so horizontal canal lies in teh vertical plane. Put the water in the ear and look at electrical activity from the electrodes around the eye when the VOR is stimulated by the fluid movement. The temperature change causes the endolymph to move and cause a nystagmus. A reduced response of under 25% is considered WNL. So need a change of >25% to make a Dx. |
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Term
| Describe how to interpret the results of caloric testing. |
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Definition
| Will result in vertigo and nystagmus in the [b]normal[/b] ear. There will be decreased or no response in the affected ear. |
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Term
| What is the big disadvantage of caloric testing? The advantage? |
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Definition
| It only gives information about the horizontal canal. It's the only test that can separate L and R sides, allowing for isolation of damaged side. |
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Term
| Unilateral caloric reduction usually indicates what? Where are the possible lesions for this response? (3) |
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Definition
| Peripheral vestibular lesion in the horizontal canal. Lesion can be in: vestibular end organ, vestibular nerve, or vestibular nerve root entry zone. |
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Term
| If there is reduced caloric response in both ears, what does that indicate? What could be the cause of it? (3) |
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Definition
| May indicated bilateral vestibular loss. some possible causes: decreased blood supply, infection - viral or bacterial. |
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Term
| What are the advantages of caloric testing? |
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Definition
| Non-physiological, can determine the side of the lesion. |
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Term
| What are the disadvantages to caloric stim? |
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Definition
| 1. results are variable. 2. can cause nausia and vomiting. 3. most patients will only do it once. 4. detects abnormalities only in the horizontal canals. |
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Term
| What are the major differences between rotation and caloric testing? |
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Definition
| Rotational is physiologic - the Sx are brought on by a normal stimulus. rotational causes bilateral simultaneous stimulation, whereas caloric testing is unilateral. |
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Term
| Describe the rotational testing procedure. |
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Definition
| Pt sits on a computer-controlled turn table, and is rotated right and left. (either the chair can rotate, or the chamber walls can rotate while the chair sits still). the VOR is tested w/ the patient being moved with their eyes open in the dark. Nystagmus is analyzed via electrodes around the eyes. |
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Term
| Which reflects the influence of the vestibular system more; the fast or the slow component of nystagmus? |
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Definition
| The slow phase of nystag more reflects the vestib system. |
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Term
| The nystagmus caused by rotational testing is analyzed for two major things. What are they? |
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Definition
| 1. Slow phase of nystagmus. 2. Gain. |
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Term
| What is Gain? What is 'normal' gain? |
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Definition
| the magnitude of the nystagmus response is compared to the magnitude of rotation to see if there is too much or too little adjustment by vestib system. Normal gain = 1:1 (eye velocity/head velocity = 1). |
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Term
| What does reduced gain indicate w/ rotational testing? Increased gain? |
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Definition
| Reduced - decreased vestib function. Increased = most commonly seen w/ cerebellar problems. |
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Term
| The walls in the chamber for rotational testing can be changed to include stripes, in the dar, dots, etc ... Why is this important? |
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Definition
| Because vestibular responses can be suppressed by relying on vision. Confusing the visual system can give a more accurate look @ vestibular system b/c vision isn't able to compensate. |
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Term
| What are the advantages of the rotational chair testing? |
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Definition
| 1. Stimulus is easily controlled. 2. Natural stimulation. 3. Rotation is tolerated better than caloric testing so subjects are willing to be retested. 4. Visual-vestibular interactions can be assessed. 5. Can vary frequencies and amplitudes. |
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Term
| What are the disadvantages of rotational testing? |
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Definition
| 1. no lesion localization. 2. proper equipment is high tech and very expensive, so not very readily available. 3. Tests only horizontal canal, like caloric testing. |
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Term
| Describe posturography motor control tests. |
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Definition
| Pt is standing, and you look at VSR and VOR response w/ perturbations. They stand on a motorized plate, and the plate moves, tips unexpectedly. EMG monitors LE muscles to test response to unexpected perturbations. |
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Term
| What is a posturography sensory organization test? |
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Definition
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Term
| What are the advantages to posturography testing? (7) |
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Definition
| 1. comparisons can be made between visits. 2. non-invasive. 3. Tests people in upright stance which is safe. 4. Tests VSR and VOR as opposed to just VOR alone. 5. Reliable as long as pts are trying. 6. no expensive equipment. 7. physiological test. |
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Term
| What is the major disadvantage of posturography? Why does this occur? |
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Definition
| 1. false positives - it may indiate a vestib problem when it doesn't exist. They might have an impaired motor response that makes them unable to respond adequately, but is completely unrelated to vestibular function. |
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Term
| What are Frenzel Goggles used for? |
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Definition
| They magnify the eyes and don't allow the pt to fixate. So they allow the PT to see nystagmus clearly. Decreasing the abilty of the pt to fixate allows us to see what the pt does when they can't compensate visually for poor vestibular function. |
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