Fig 1.
Exemplary illustration of the used methods.
(A) Determination of IED extent. The red circle indicates the IED with the highest negativity, the blue circle indicates IEDs with at least 50% of this negativity and the green circle indicates IEDs that did not meet the inclusion criteria. (B) Representation of possible inter-spike variability within one IED set.
Table 1.
IED and BOLD extent.
Fig 2.
Example 1 for better representation of the BOLD-topography with 64 electrodes.
27-year-old patient (patient 6, study 3) with left structural frontal lobe epilepsy. The patient underwent a previous operation with frontal resection, which showed a FCD type 2a. No seizure freedom could be achieved through operation. This is a typical example for the superiority of the 64-channel-EEG. The 32-channel EEG reveals a left temporoparietal IED area (A). The 64-channel EEG shows that left frontotemporal regions are as well included in the IED area (B.) The extensive positive BOLD response on the left hand side exactly reflects the IED distribution from temporoparietal to frontotemporal as shown in the 64-channel EEG. The white arrow indicates the relevant positive BOLD response (C and D). (E) shows different IEDs of one IED set.
Table 2.
Clinical information.
Fig 3.
Example for correlation between PET and positive BOLD response.
26 year old patient (patient 2) with structural epilepsy. PET shows a discrete temporal and parietal hypometabolism. The strongest positive BOLD response in MREG is located temporal on the right hand side and therefore shows a good correlation with PET.
Fig 4.
Representation of the positive correlation between IED and BOLD extent.
The x-axis shows the in the IED extent included number of electrodes. The y-axis once shows the volume of positive BOLD responses (A) and once the number of positive BOLD clusters (B) in MREG. Patient 8, study 1 reveals a restricted frontal IED area in the EEG (C), concordant to the left focal positive BOLD response in MREG (E). Only few other clusters are visible, all of them focal. In comparison, patient 16, study 2 reveals a widespread IED area in the EEG (D) with the highest negativity over F2 and multiple, widespread BOLD clusters in MREG (F). However, the BOLD response located at the front is concordant to the most negative IED area over F2 and the MRI results.
Fig 5.
Example 2 for better representation of the BOLD-topography with 64 electrodes.
71-year-old patient (patient 10, study 3) with structural temporal lobe epilepsy. Another example for the predominance of the 64-channel-EEG. The 32-channel EEG reveals a temporoparietal IED area (A). The 64-channel EEG shows that the IED area as well spreads into frontotemporal regions (B). The positive BOLD response on the right hand side represents the IED distribution from temporoparietal to frontal regions as shown in the 64-channel EEG. The white arrow indicates the relevant positive BOLD response (C and D).
Table 3.
Detailed representation of BOLD effects and comparison between 32/64 channel EEG.