1 epilepsy, why needed Parameters of Electrocorticography in

Introduction of Electrocorticography Parameters in epilepsy surgery.

Electrocorticography {ECoG} is a modality of neurophysiological monitoring {IONM}, we use in epilepsy surgery to record electrical activity directly from the surface of the brain. It helps to identify the location of seizure activity and guide the surgical resection of the epileptic focus/seizure zone.

How to place the recording electrode in epilepsy surgery.

Electrodes to be placed directly on the surface of the brain during surgery{surgeon does only}.The number and placement of electrodes depend on the specific surgical procedure and the area of the brain being monitored. Note- One corkscrew electrode should be placed on the head as a reference , little away from the surgical field because grid and other depth electrode act as a active . Ground electrode to be placed near to recording side to eliminate the electrical artifact.

Rate of Sampling.

The sampling rate is the frequency at which the electrical signals are recorded .A higher sampling rate allows for more detailed information about the electrical activity of the brain.

How to set Filter in epilepsy surgery.

Electrocorticography signals are often filtered to remove noise and artifact that may interfere with the analysis of the data. Low-cut approx. 0.3Hz and high-cut 70 Hz filters are commonly used to isolate the desired frequency bands and 50-60 Hz electrical artifacts, along with time constant 0.6. {Note-low cut filter vary according to time constant .} sensitivity usually start from 20-30 microvolt/division or can be adjusted according to waveform and depth of anesthesia.

Conclusion.

Intraoperative ECoG is a widely used and well established modality for the surgical treatment of intractable epilepsies. This technique provides real time information regarding the specific locations of epileptiform activity that may be associated with the seizure foci or epileptogenic zone. Above parameters will vary on epileptologist, in our practice a neuro-medicine doctor usually comes to interpretate the signals

Q-What are technical challenging to record ECOG and Mapping?

A-First we need at least 32 channel amplifier to record both mapping and ECOG recording

Q-Why important proper grounding ?.

A– To eliminate the electrical artifact.

Q-Muscle relaxant can be used?

A-While only ECOG NMJ Blocker is useful ,when motor mapping as well than no.