EEG Chih Ho Chou Department of neurology
EEG
Chih Ho ChouDepartment of neurology
EEG Physiology
• Distrubuted neuronal networks assure correct functioning of the human brain.
• Inhibitory and excitatory feedforward and feedback processes are basic mechanisms
Basic Interpretation
• Standard 10-20 or 10-10 system
• Awake and resting
Montage
• Reference montage• Bipolar montage Anterior-posterior bipolar montage (double
banana montage) Transverse montage (E-montage) C-montage A1-A2 montage
Calibration
• Time constant
• Sensitivity: 紀錄腦死時 sensitivity 需提高至
2 μV/mm
• Amplitude linearity
Frequency filter
• 低頻截頻器 : 濾去過慢頻率之腦波 ( sweating…)
• 高頻截頻器 : 濾去過快頻率之腦波 (muscular artifacts…)
• Notch filter: 濾去 60 Hz 交流電
Normal rhythms
rhythm (8-13 Hz occipital region, visual blocking)
rhythm (14-30 Hz) classification of frontal, widespread type, and posterior type (sometimes called fast alpha variant because of visual blocking)
• γ rhythm (>30), very low amplitude, technically difficult to study. Cognitive activity “dynamic”
rhythm (sharp transient of sawtooth shape and of pasitive polarity in the pccopital regions, looking at image containing visual details. VEP)
• Mu rhythm (arch-shaped, 7-11Hz, paracentral area, blocked by voluntary or passive movements)
Abnormal activities
• δ activity (4-7 Hz)
• Θ activity (<3 Hz)
Artifacts
• Physiologic effects
1.from cardiovascular system
EKG artifact
pulse artifact
ballistocardiogram
2.respiratory artifact
3.sweating artifact
4. EMG artifact
5. Eye movement artifact
6. glossokinetic artifact
7. body movement artifact
• Mechanical artifact
electrode pop
60 Hz artifact
• Environmental artifact
static electricity
plug artifact
Activation procedure
• Chemical activation hyperventilation drug: diazepam…• Input modification photic stimulation auditory somatic• State related to biological rhythm sleep sleep deprivation
• 懷疑為 absence seizure, 一定要做hyperventilation
• 懷疑為 juventile myoclonic epilepsy, 一定要做 photic stimulation
• 懷疑為 temporal seizure, 一定要做 sleep EEG
癲癇發作怎麼辦 ?
• 立即停止誘發• 保護病人為原則 不必硬塞東西到患者口中 不必強壓患者手腳 不必馬上送急診 , 除非是大發作癲癇重積
狀 態