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19 Cards in this Set
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- Back
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What do EMG results show?
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eye movement quality (quick?) and quantity (velocity)
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What is the difference in appearance of the EMG when comparing innervational problens vs mechanical prob?
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mechANICAL: good velocity and normal square wave (position)
innervational: reduced velocity and sloping square wave |
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How does an EMG work??? (VERY BASIC)
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The retina has an overall negative charge relative to the cornea which has an overall positive charge. Movemet of the eye is detected as the eye changes direction and looks toward a different electrode
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What are some oither findings that can help you diagnose mechanical vs innervational problems (in addition to the EMG)?
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forced ductions
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how is the paretic muscle compared to its antagonist muscle?
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calculate percent differences of avg velocity of 4 or 5 "good" saccades of each muscle to get % difference:
avg of paretic muscle - avg of antagonist muscle divided by the greater of the 2 |
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How is a paresis distinguished with EMGs?
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percent difference of greater than 29% is abnormal
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three main types of neurons used to generate saccades are:"
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burst cells - fire immediately prior to and during horizontal saccade (excitatory)
inhibitory burst neurons send acons across to the yoke muscle pause neurons - ON when NO saccades happening. tonic neurons - keep eye in position after saccade |
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latency of a typical saccade?
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200 ms
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peak velocity of a saccade>
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700 deg per sec
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normal smooth pursuit looks like
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sine wave - position only
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what is a hypermetric saccade>?
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overshoot the target - step up - down
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what is a hypometric saccade?
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undershoot the target - steps up
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latency of a typical saccade?
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200 ms
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peak velocity of a saccade>
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700 deg per sec
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normal smooth pursuit looks like
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sine wave - position only
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what is a hypermetric saccade>?
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overshoot the target - step up - down
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what is a hypometric saccade?
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undershoot the target - steps up
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What type of eye movements can you observe for in ERGs?
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nystagmus
dysmetria abnormal pursuit/OKN small intrusions on fixation subclinical findings |
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How can you confirm a suspedted case of myasthenia with lees screen?
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tensilon test
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