1. Localization and Assessment of Epileptic Foci
A new method using Wavelet Packets
Tomer Gazit (BIU & TAU)
With
Itai Doron, Eden Rephaeli (TAU)
Eshel Ben-Jacob (TAU)
Oren Sagher – Dep. Of Neurosurgery, Univ. of Michigan Health System
Leo V. Towle – Dep. Of Neurology, Univ. of Chicago Hospitals
Epilepsy Workshop, Michigan, May 9

2. Outline Introduction – the localization problem The method Results
New insights and conclusions

3. Invasive Recordings - Subdural EEG (ECoG)
1-3 weeks recordings
Voltage
Time

4. Invasive Recordings – Depth Electrodes
1-3 weeks recordings

5. Inter-ictal Onset Ictal
The Challenge:
Localization and assessment of the Epileptic foci
Inter-ictal
(before the seizure)
Onset
Ictal
(The seizure)

6. The Classical Frequency Bands
Delta: <3.5 Hz
Theta: Hz
Alpha: 7-13 Hz
Beta: Hz
Gamma: >30 Hz

7. The Big Picture Similarity
42 HZ
In all successful surgeries, the method detected the correct foci
Frequency
0 HZ
Similarity

8. Time-Frequency Analysis – Some Math
Power
Voltage
Time
Frequency
The Fourier Transform
Frequency basis
Time basis

9. Beyond Fourier Transform Time-Frequency Analysis
plane
Frequency
Time
Signal

10. Wavelets A “mother wavelet”
is a function located in time and frequency.
The Mexican Hat
The function is dilated and time-shifted
to form a set of basis functions:
The Coiflet

11. The Wavelet Transform
Wavelet basis
Binary tree

12. Wavelet Packet Decomposition
Maximum Information
Best Basis 70 31 32 11 12 13 4 9 8 2 3 5 6 7
(70)36
(31)23
(32)13 11 12
(13)9 4 9 8 2 3 5 6 7
“Shannon Information” Like
Doron et al. Time-Invariant Person Specific Frequency Templates in Human Brain Activity,PRL. 96 (2006)

13. Quantifying the Similarity
1/16
2/16
4/16
3/16 Wn

14. Inter-Ictal Analysis: Similarity Matrices
Type I
Type II

15. Type I
Type II

16. Type I - Comparison
Failed – the focus could not be removed

17. Type II- Comparison Failed Partially successful Successful

18. In all the successful surgeries
Results - 11 Patients
Type I
Type II
7 Patients
4 Patients
6 successful surgeries
1 successful surgery
1 Failed
(Focus could not be removed)
3 Non-successful
In all the successful surgeries
the resected zones matched the predicted foci
In all the non-successful surgeries
One (or more) predicted focus was not resected

19. Type I
Type II

20. Dynamics of Multiple Foci – For type II
Looking Ahead
The Middle Ages
The Iron Age
The patient survived the surgery
Can we do better?
Dynamics of Multiple Foci – For type II
Early Warning
Scalp EEG
Epilepsy Pace-Maker

21. Thank you Summary The “world best method”
New methods for:
Localization and Assessments of Epileptic Foci
1. Identification of two Types of Seizure Dynamics
2. Satisfying agreement with surgery results
3. New insights
We do not seek:
The “world best method”
and not to replace the Epileptologists
We hope that one day
The methods will be used for diagnostics
Thank you