Table 2.

Methodology of EEG recordings: location vs. type of electrode.

Location of recordings	Scalp/Epicranial (Skull intact)	Epidural (over the dura, dura intact)	Subdural (Subdural space)
Type of electrodes used	Wire-gold-plated/silver/silver-chloride/tin/platinum/stainless steel helix Contact – C-shaped loops/flat ends	Wire/Stainless steel screws/stainless steel helix
Dos for type of electrode	Gold electrodes are better for polysomnography because they accentuate the slower frequencies. Silver electrodes are better for EEG and epilepsy studies. Chlorinated silver electrodes record EEGs better than unchlorinated silver electrodes. Tin conducts more efficiently and is less costly.	Self-tapping screws with blunted tips
Don’ts for type of electrode	Mix different metal electrodes for any given recording or use wires with different diameters.	Mix different metal electrodes for any given recording or use wires with different diameters.
Pros for location	Lower risk of injury to CNS/infection	Low impedance/lower contamination with movement artifacts	Lower impedance/lower contamination with movement artifacts
Cons for location	Higher impedance, movement artifacts, difficulty in associating recording to any specific brain region.	Higher risk of injury to CNS/infection/scar tissue formation in chronic recording that increases impedance