Fisch EEG Primer Chapter 2 Flashcards
Recording Electrodes
Most common electrode types used
metallic discs or cups typically 4-10mm in diameter - same electrodes should be used for all recording locations
Needle scalp electrodes
no longer recommended for routine clinical use
Purpose of nasopharyngeal and transphenoidal electrodes
attempt to records activity from inferior temporal lobe - usually placed by physician since it often requires anesthetic sprays
NOTE: epileptiform discharges produced ONLY at nasopharygeal leads are artifact until proven otherwise
Materials used for recording electrodes
coated with gold, Chlorided silver, tin, platinum or any substance which does not react electrically with the electrolytes of the scalp
Typical electrical impendences should be in the range of
100 - 5000 ohms
EEG impendence greater than 5000 ohms can
attenuate the EEG and cause a 60Hz interference
EEG impedence less than 100 ohms often results from
accidental short circuits between electrodes
placement of electrodes should follow
the international 10-20 (21 recording sites) or modified 10-20 systems - these use bony landmarks for reproducible recordings
What is the purpose of recording non-cerebral potentials
detecting and identifying articats that contaminate the EEG of for monitoring other bodily functions
Electrocorticographic ball or wick electrodes
used during neurosurgical procedures, usually excision of epilptogenic foci
Subdural or Epidural Electrodes
used to localize epileptiform activity and to map cortical function - subdural grids can also be used stimulate underlying cortex
Depth Electrodes
used for EEG recording of deep structures, to define targets for surgical destruction, and for placement of stimulating electrodes for treatment of movement disorders
international 10-20 abbreviation “Fp”
Prefrontal/Frotopolar
international 10-20 abbreviation “F”
Frontal
international 10-20 abbreviation “C”
Central
