Dear all,
I performed source localization on one subject for several interictal spikes with OpenMEEG and Sloreta. Only simnibs has allowed me to segment correctly my cortex including the tumor tissue. This is to write a case report about SEEG in the OR before glioma resection for this patient.
I read this tutorial page
and i understood that SLoreta does standardize the results and that i can report the average results as epileptogenicity mapping from interictal spikes. Could you please confirm?
Thank you
Anne-Cecile Lesage, PhD
Research Scientist
Department of neurosurgery
University of Texas Medical Branch
anlesage@utmb.edu
Hi @aclesage
Sorry for the delayed response.
I performed source localization on one subject for several interictal spikes with OpenMEEG and Sloreta. Only simnibs has allowed me to segment correctly my cortex including the tumor tissue.
Can you explain what do you mean only simnibs segment correctely the tumor tissue? Please be aware that the main segmentation tools are mainly for healthy brains, and Simnibs team reported that their tools are only fully tested on healthy brains.
Also, could you clarify how OpenMEEG fits into your pipeline? SimNIBS generates an FEM mesh, whereas OpenMEEG is a BEM solver, so a SimNIBS FEM mesh cannot be used directly with OpenMEEG. It would be helpful if you could describe the processing pipeline you used.
In any case, the method used for the forward computation will not affect how the sLORETA normalization or averaging should be interpreted.
This is to write a case report about SEEG in the OR before glioma resection for this patient.
So this is important to ensure the pipeline is correct.
and i understood that SLoreta does standardize the results and that i can report the average results as epileptogenicity mapping from interictal spikes.
The first part of your sentence is correct. If your interictal spikes originate from the same generator and are aligned consistently (e.g., at the spike peak), averaging the standardized source maps is a reasonable way to summarize the results.
However, I would be cautious about referring to the resulting map as an "epileptogenicity map."
Source localization of interictal spikes is generally interpreted as an estimate of the irritative zone, but is not necessarily identical to the epileptogenic zone which are mainly computed using other methods.
@yashvakilna Any further explanation for the last part?
@tmedani That was a nice summarization. And the questions that you posed are also quite relevant, since answering them would help us understand the context of computing sLoreta.
@aclesage Localizing epileptic spikes would indeed lead to estimating the "Irritative Zone", which is not the same as the "Epileptogenic Zone" or the "Seizure Onset Zone". Also, creating Epileptogenicity maps would require recording a seizure, not just epileptic spikes.