#Anchor-1 "FAQ"

Frequently Asked Questions (FAQ)

What are the benefits compared to the clinical practice?

Unlike ECS, cortiQ does not produce artificial seizures. CortiQ cannot produce dural pain caused by bad electrode contact. CortiQ shows the neural areas involved in a given task and allows very fast pre-screening that may be used for planning ECS mapping and surgical removal of affected tissue.

Who will benefit from the system?

Neurosurgeons who want to get additional information about the eloquent cortex and other specific regions, and research groups who want to investigate functional regions of the cortex. Neurosurgeons also benefit from cortiQ’s ability to provide maps in real-time instead of hours or days. Patients benefit from reductions in the time needed for mapping, need for additional mapping procedures, chance of accidental seizures resulting from ECS, and the risk of accidental removal of too little or too much brain tissue.

How does the system work and what do the results mean?

The system compares high-gamma activity in the ECoG during resting and active conditions. Changes in the power of the high-gamma band indicate activated neurons with respect to the electrode position. A group of highlighted electrode groups shows an activated neural network. The system updates the activation map in real-time. This allows the user to interpret the activation during the experiment and to stop the paradigm anytime. The longer the paradigm lasts, the more noise is eliminated, and hence only task-related electrodes are highlighted. A recommended setup contains around 45s active and 45s resting state per task.

What is the mapping quality index (MQI)?

The MQI represents the highest change in power of the high-gamma frequency band from a baseline period compared to an active period within a mapping session. The derived metric is the coefficient of determination (R²) in percentage, where an MQI > 10% indicates significant results for a standard mapping paradigm.

What information is used to perform the mapping?

The power of the high-gamma frequency band (60-170Hz) derived from electrocorticographic (ECoG) signals.

What does the size of the bubbles mean?

The size of the bubble indicates the activation of the tissue underneath an electrode. All bubbles are normalized to the electrode showing the highest activation. The color of a bubble changes with its size (the bigger the brighter). The maximum size of a bubble is normalized to the mapping quality index (MQI).

Why show results in real-time?

The supervisor can immediately check the quality of the mapping session and stop/change the paradigm at any time. No further offline processing is necessary.

How can the mapping result be compared with other methods and ECoG analysis?

cortiQ stores the recorded EEG synchronized with the mapping paradigm and provides an importer for MATLAB (The MathWorks Inc., USA). cortiQ mapping results are stored in CSV format for further comparison.

Does the mapping work with stereo-EEG or depth electrodes? Why show results in real-time?

The mapping procedure is intended to locate functional cortical regions. In principle it is possible to derive the same features (high-gamma band power) with depth electrodes, but it is recommended to have more than 20 electrodes in contact with the cortex.

What useful information can we get with cortiQ in addition to the ECS?

The activated neural network is highlighted based on natural behaviors, such as speech or movement. The ECS can only investigate symptoms caused by local dysfunction due to electrical stimulation.

Is it possible to do ECS with cortiQ?

Yes, g.tec provides a cortical stimulator for electrically stimulating the brain during a functional mapping procedure. The stimulator will be fully integrated into the mapping software in the future.

What is the goal of your system?

Support surgeons’ planning for brain surgeries by providing additional information about functional brain regions.

Is language mapping possible?

Yes, cortiQ comes with a passive listening paradigm that maps the auditory cortex, including the receptive language area, and it can play back language related paradigms like picture naming tasks and map expressive language related cortical regions. Already published mapping results can be found in the Publications section.

How long does the mapping last?

A mapping that highlights four activation maps usually lasts about 6 min.

What is necessary to set up the mapping, and which hardware is required?
  • g.tec’s amplifier – g.HIamp
  • g.tec’s Headboxes or splitterboxes (for parallel measurements) to the electrodes with 1.5 mm medical safety connectors. – g.HEADbox
  • g.tec’s software - cortiQ
  • g.tec’s Electrical Cortical Stimulator – g.Estim PRO
  • g.tec’s Switch matrix box to be able to record and stimulate without the need of changing the electrode grids – g.Eswitchbox
  • The system uses the implanted electrodes that are necessary for clinical neuro-monitoring