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