A profile on the WISE cortical strip for intraoperative neurophysiological monitoring

Figures & data

Table 1. Devices that are commercially available.

Name	Manufacturer	Film thickness [µm]	Strip substrate material	Contact structure	Contact material	Contact diameter [mm]	Impedance [kΩ]	FDA clearance	FDA clearance year	CE mark
Wise Cortical Strip	WISE S.r.l.	250 µm	Silicone	Embedded thin film	Platinum	4.0 mm	2.7 kΩ	K221123	2022	yes
Subdural Electrode	Ad-Tech Medical Instruments Corporation	800 µm	Silicone	Metal foil	Platinum or Stainless Steel	4.0 mm	5.3 kΩ	K053363	2014	yes
Cerebro – Multilayer Cortical Electrode	Spes Medica	From 200 µm to 500 µm	Polyurethane	Metal foil	Platinum or Stainless Steel	3.0 mm	n.a.	K211954	2022	yes
Cortex Strip Electrode	Inomed Medizintechnik GmbH	800 µm	Silicone	Metal foil	Stainless Steel	4.5 mm	n.a.	-	-	yes
Cortical Electrodes IOM	DIXI Medical	450 µm	Silicone	Metal foil	Stainless Steel	4.0 mm	n.a.	K201931	2021	yes
Cortac Grids & Strips	PMT Corporation	760 µm (strip) or 500 µm (grid)	Silicone	Metal foil	Platinum or Stainless Steel	4.5 mm	n.a.	K082474	2009	yes
Evo Electrode	NeuroOne	80 µm	Polyimide	Superficial thin film	Platinum	variable	n.a.	K192764	2019	-
AirRay subdural cortical electrodes	CorTec GmbH	500 µm	Silicone	Metal foil	Platinum-Iridium	variable	n.a.	K183437	2019	-
Blackrock NeuroCoG Subdural Cortical Electrodes	Blackrock Microsystems	Unknown	Silicone	Metal foil	Platinum-Iridium or Stainless Steel	variable	n.a.	K191346	2020	-

The flexibility of an electrode can be estimated from the thickness of the substrate material. Not available n.a.

Figure 1. ECoG electrodes in the surgical field.

The WCS electrode (right) has dark platinum electrode contacts embedded in the carrier material. A standard electrode (Ad-Tech, left) has electrode contacts that are platelets made from platinum foil [30].

Figure 2. Impedance and noise level. (a) The median impedance was 6.9 kΩ for Ad-Tech and 3.4 kΩ for WCS measured at 140 Hz.

(a) Linear spectral density (LSD) of the raw signal. Across all frequencies, the LSD of the WCS electrode (blue) was higher than the LSD of the Ad-Tech electrode (red).

(b) Example of an evoked HFO event with small amplitude. The small amplitude did not exceed the noise level of the Ad-Tech (blue lines), resulting in (SNR = 0.9 < 1) and the event went undetected. With the reduced noise level of WISE (red lines), the SNR increased to SNR = 1.6 > 1 and the HFO was detected. Adapted from [30].

Dimakopoulos V, Neidert MC, Sarnthein J. Low impedance electrodes improve detection of high frequency oscillations in the intracranial EEG. Clin Neurophysiol. 2023;153:133–140.

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