a Myasthenia repetitive 3 Hz stimulation results in decrement of CMAP With

A myasthenia repetitive 3 hz stimulation results in

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a.Myasthenia: repetitive 3-Hz stimulation results in decrement of CMAP ; With exercise, CMAP can improve for first min, but then worsen in 4-6 minb.c. Botulism: Baseline CMAP smaller with repetitive stimulation; no change with exercise.
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EMG findings in neuromuscular diseases.Conduction VelocityAmplitudeF & H LatencyDistal LatencyFibrillationsAxonal damage>70%↓~↑nl↑PNS demyelination<50%~↓↑~↑VariableLMN dz>70%↓ motor~cnl↑UMN dznlnlnlnlNoneRadiculopathy>80%~↓↑nl↑NMJ dznlnl/↓nlnlNoneMyopathynl~↓nlnlNone
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Electroencephalography(EEG)..
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EEGA.What is EEG/Electroencephalography?"B.What does the EEG tell us?1.General health of the brain2. Epilepsy
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.A. What is EEG/ Electroencephalography?"Measuring of brain wavesThe electrical activity of the brain is easily recorded from electrodes placed on the scalp. The potential difference between pairs of electrodes on the scalp (bipolar derivation) or between individual scalp electrodes and a relatively inactive common reference point (referential derivation)
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EEG cont'dHarmless and painless investigationTakes ~20-30 minutesSome provocation method usedHyperventilationPhotic stimulationSleep deprivation-sleep EEG
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EEG cont'dElectrodes are put on the scalp Measure the difference in potentials between two points on the scalp.oGenerally 21 electrodes and two references on ears applied according to proscribed systemoPen deflections represent differences in electrical potentials between the two electrodes involved in a given channel
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EEG cont,d
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From WyllieEEG cont,d
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EEG cont,d
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Unipolar vs. Bipolar montage
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EEG cont,dTypes of wavesAlphaBetaThetaDeltaNormal variationsAge, Sleep, Epileptiform dischargesSharp wavesSpikesSpike-wave complexes
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Beta: >13 Hz;usually diffuse lowVoltage:increase with sedatives,Light sleepAlpha: 8-12 Hz; the posterior basic rhythm;At age 3 reaching 8 Hz; at age 10, 10 HzAbnormal if amplitude asymm. >50%Theta: 4-7 Hz; small amts. nl; increasesWith drowsiness, hyperventilationDelta: 0-3 Hz; posterior slow waves of youthNl; normal in sleep; focal delta=local abnl.
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  • Fall '19
  • Evoked potential, Electroencephalography, Event-related potential, Motor unit

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