脑电图

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PRINCIPLE 2
• The structure and chemical composition of neurons (or brain cells) leads to the generation of an electrical potential • EEG has the ability to measure this electrical activity during normal and pathological states. • Obtaining EEG data consists of connecting bioelectric electrodes from the scalp (or exposed brain) into a machine capable of amplifying these microvolt (µv) signals so that they may be recorded on paper or recorded digitally.
– video games – visual patterns
• AED withdrawal
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STRENGTH AND ADVANTAGES OF EEG
• Is a measure of brain function • supplement neuroimaging studies • Provides direct rather than indirect evidence of epileptic abnormality • May be the only test that shows abnormalities in epileptic patients • Provides some spatial or localization information • Low cost • Readily repeatable • Portable / ambulatory
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Adenosine Triphosphate (ATP) provides energy for proteins to pump 300 sodium ions per second out of the cell while simultaneously pumping 200 potassium ions per second into the cell (concentration gradient)
ELECTROENCEPHALOGRAPHY
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OUTLINE
• Step 1: definition, history, principle, electrode placement, pros and cons, clinical use • Step 2: EEG wave, types, rhythm, background activity • Step 3: abnomal EEG, factors • Step 4: EEG and disorders • Step 5：to be noted
刺激（睁眼等）时不出现一侧或两侧性抑制。 5）基本节律的波幅在左右对称部位之间有恒定的 20%以上差异时，或者左右对称部脑波动平均频 率（或平均周期）有10%以上的差异时。
6）出现棘波、尖波、棘慢复合波、尖慢复合波等异 常波时。
• Thus making the outside of the cell more positively charged and the neuron negatively charged. This rapid ionic movement causes the release of action potentials
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CLINICAL USE- ROUTINE EEG
• to distinguish epileptic seizures from other types of spells • to differentiate "organic" encephalopathy or delirium from primary psychiatric syndromes • to serve as an adjunct test of brain death • to prognosticate, in certain instances, in patients with coma • to determine whether to wean anti-epileptic medications
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HISTORY
1875 – Richard Caton from Jena, Germany discovered electrical brain activity by probing the surface of exposed brains of animals using a primitive version of the galvanometer.
• Frequency • Amplitude • Spatial distribution
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FREQUENCY AND PERIOD (DURATION)
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AMPLITUDE
• • • • μV 1mm→10 μV waxing and waning symmetry
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ROUTINE EEG TECHNIQUES
Routine
• Eye opening and closure • Hyperventilation • Intermittent photic stimulation
– 1, 5, 10, 15 & 20 Hz
Optional
• Sleep deprivation • Sedated sleep • Specific methods of seizure precipitation
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DIFFERENT TYPES OF BRAIN WAVES IN NORMAL EEG
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DESYNCHRONIZATION OR ALPHA BLOCK
• Eyes opening (after closure) • Thinking by the subject (mathematical calculation) • Sound (clapping )
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RHYTHM
8.5Hz αrhythm
10Hz αrhythm
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BACKGROUND ACTIVITY
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PAROXYSMAL RHYTHMIC WAVES
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STEP 3
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异常脑电图的诊断标准-1
成人具下列标准的任何一项者属于异常：
1）基本节律的优势频率在8Hz以下的慢波带以及稀 有优势的基本节律在14Hz以上的高波幅快波带时 （低波幅快波图像一般属于正常）。
Dr. Hans Berger
1920’s – Hans Berger recorded human EEG with string galvanometers using subjects with holes in their skulls. He discovered waves at 10 Hz (named them Alpha waves because they were the first he isolated in the human EEG).
2）基本节律中混有非爆发性的慢波时，混有0.5～ 3Hz的δ波时为异常。慢波为4～7Hz的θ 波如果显 著出现，应大致考虑为异常。特别是有局灶性慢 波者。
3）基本节律的平均波幅异常高时，或者相反地基本 节律完全平坦，或只有低波幅不规则的慢波出现 时。
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异常脑电图的诊断标准-2
4）构成基本节律的波，即使给予各种各样的觉醒
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INTERNATIONAL 10-20 SYSTEM OF ELECTRODE PLACEMENT
• Established in 1958 • Electrodes are spaced at 10% or 20% of distances between specified anatomic landmarks • Odd number electrodes over left and even number over right hemisphere
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SPIKE AND SHARP WAVE
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MUTIPLE SPIKE, POLYSPIKE
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SPIKE-AND-SLOW-WAVE COMPLEX
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MULTIPLE SPIKE-ANDSLOW-WAVE COMPLEX
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SHARP SLOW WAVE COMPLEX
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CLINICAL USE- LONG-TERM MONITORING
• to distinguish epileptic seizures from other types of spells • to characterize seizures for the purposes of treatment • to localize the region of brain from which a seizure originates for work-up of possible seizure surgery