stereo EEG indications, description and usefulness in drug resistant epilepsy evaluation

1. SEEG IN SURGICAL EPILEPTOLOGY:
“ONE MUST USE SEEG FOR iEEG MONITORING”
VIKASH AGARWAL
PDF( Epilepsy)SCTIMST - 2012
Fellowship in Movement Disorders & DBS
(University of Malaya Medical Centre, KL,Malaysia)- 2019
CONSULTANT NEUROLOGIST
GLENEAGLES GLOBAL HEATH CITY,CHENNAI
STEREO EEG MENTORSHIP BY DR DINESH NAYAK

2. SEEG for iEEG monitoring -
• SEEG schools of thought
• Advantages & Safety
• Epileptogenic network
• Functional Mapping
• Insular Epilepsy
• Interictal and Ictal onset SEEG patterns
• Hypermotor Sz (HMS) & SEEG implantations
• Conclusion

3. • 1950s St.Anne’s Hospital in Paris
Bancaud and Talairach
“3D extent of dysfunctional
brain tissue surrounding
intraparenchymal brain
tumours, and more
specifically, to define
epileptogenic tissue”
INTERICTAL SEEG DATA ONLY
UNILATERAL , HYPOTHESIS
• 1960s Crandall , UCLA
USED EEG TELMETRY DEVICE
DEVELOPED BY NASA , TO
STUDY MESIAL TLE !!
LONG TERM ICTAL SEEG
RECORDINGS , B/L
IMPLANTATIONS
JEROME ENGEL , BRAIN,2016

4. WHAT MADE SEEG LESS POPULAR TRADITIONALLY?
 need for a cathether based angiography
 manual burden on the surgeon to change and fix individual trajectories
 lack of familiarity of SEEG data interpretation.
MODERN TIMES !!!
 MRI /CT based coregistration ( Stealth Station 8- S8, Medtronics)
 Robotic steriotactic platform ( ROSA) allows multiple and more complex
electrode placements
 More centers for training for surgeons to learn the Steriotacxy skills

6. TYPICAL SEEG IMPLANTS FOR MESIOLIMBIC TEMPORAL
• LA- MTG TO AMYGDALA
• LH- MTG TO MID HIPPOCAMP.
• LP - MTG TO POST HIPPOCAMP.
MESIOLATERAL OR LATEROMESIAL RELATIONSHIPS CAN BE STUDIED

7. SEEG IS LESS INVASIVE THAN GRID/STRIPS
 bilateral implantations
 disparate brain areas , dual pathology
 mesial structures
 deeper structures like insula, cingulate
can be safely done for failed cases with prior craniotomies

8. • 69 adults , 47% lesional cases
• Reason- 76% non localising ictal
onset
• 41 resective surgery
• 61% Engel Class I outcome

9. SAFETY OF SEEG VS GRID
SYMPTOMATIC HAEMORRHAGE -
• 549 SEEG implants 2.2% , 0.4% FOR DEFICITS,0.2% DEATH - McGovern et al ,2019
• SUBDUAL GRIDS - OVERALL 4% , 3.5% NEEDED EVACUALTION - Arya et al ,2019 ( Metanalysis)
No difference in risk of haemorrhage with all types of stereotaxy - catheter based , CT,MRI or Robotic
INFECTIONS
 0.8% vs 4% for SDE
 small burrholes
 SDE infections requires surgical evacuation, even bone flap can get infected
 SEEG infections usually resolves with antibiotics conservatively
HARDWARE MALFUNCTIONS
• 0.4% in SEEG VS 1.5% for SDE
McGovern RA, Ruggieri P, Bulacio J, Najm I, Bingaman WE,Gonzalez-Martinez JA. Risk analysis of hemorrhage in stereo-electroencephalography procedures. Epilepsia. 2019;60(3):571–580
Tandon N, Tong BA, Friedman ER, et al. Analysis of morbidity and outcomes associated with use of subdural grids vs stereoelectroencephalograpy in patients with intractable epilepsy. JAMA
Neurol.2019.
Arya R, Mangano FT, Horn PS, Holland KD, Rose DF, Glauser TA.Adverse events related to extraoperative invasive EEG monitoring with subdural grid electrodes: a systematic review and meta-
analysis.Epilepsia. 2013;54(5):828–83
Mullin JP, Shriver M, Alomar S, et al. Is SEEG safe? A systematic review and meta-analysis of stereo-electroencephalography-related complications. Epilepsia. 2016;57(3):386–401.

10. SAFETY OF SEEG FROM CALGARY DATA

11. SAFETY IN CHILDREN -
• 78% of patients with a low
probability of having surgery
before SEEG received surgery
• 67% Engel Class I outcome
• lower rate of complications
(vs SDE)

12. “series or parallel”
- Time frequency analysis/EI
- Connectivity analysis /h2
- Causality analysis /coupling
- Graph theory applications

13. FROM EPILEPTOGENIC FOCUS TO NETWORKS“
NETWORKS”
EZ RESECTED
ONLY IOZ ( 27%)
IOZ + NEARBY CORTEX
OF EARLY SZ SPREAD
( 73%)
Kahane et al.,2006

14. • Electrode depths - HITS - 7.35mm
• 424 SEEG electrodes
• 34 ( 12%) hits in SEEG , 98 (39%) hits in
Grid ( all on dominant L,except 1 case )
• 10 SEEG - 7 resection + 3 ablative
• 6 cases DES ONLY by SEEG but no post
op language deficits with 7mm cut off for
language mapping
• most studies discordant data due to
reproducibility issues

15. DIRECT INSULAR STIMULATION DATA- SEEG
Isnard et al.Epilepsia.2004
6 cases of pure insular epilepsy
a. somatosensory
b.viscerosensitive
c.layrngeal constriction
d. audiotry responses
e. speech
f. others like sensation of
unreality,levitation,whole
body sensations

16. • HPE PROVEN FCD ALL CASES ( OF 500
SURGICAL CASES)
• EARLY CASES BETWEEN 1964 - 1994
• TOTAL 28 CASES OF SEEG
• GOOD CORRELATION BETWEEN SEEG
EZ AND HISTOLOGICALLY DEFINED FCD
82%
64% SURGICAL OUTCOME
• MRI BRAIN ONLY IN 7 CASES
• 10 CASES CT SCAN BRAIN
• EARLY ONSET FOCAL EPILEPSY
• COMPLETE RESECTION
• ICTAL ONSET DISCHARGE INCLUDED IN
FINAL RESECTION
• NO DYSPLASTIC TISSUE AT RESECTION
MARGIN
64% TIMES FCD TISSUE IN MESIAL
ASPECT OF BRAIN

17. INTERICTAL INTRALESIONAL SEEG RSD TYPES IN FCD
• CONTINUOUS OR SUBCONTINUOUS
INTRALESIONAL DISCHARGES
• 1 - 10 HZ
• SEEN IN ALL PATIENTS WHO HAD
INTRLESIONAL ELECTRODES ( EVEN IF
THE SCALP EEG NEGATIVE IN THAT
REGION)
• PSUDOPERIODIC DISCHAGRES ( SEVERE
FORM OF INTERICTAL SEEG )

19. ICTAL PATTERN & SURGICAL OUTCOME

20. ICTAL PATTERNS DEPEND ON THE LESION TYPES
• FCD type 1, NDT - pattern 5/6
• pattern 1/ 2/3/4 best results
• 2 types oscillations
1. low voltage fast oscillations
2. high amplitude slow rhythmic
paroxysms

21. EG onset
LESION ANTR
SENS-MOTOR
CING ANTR
CING MID
INSULA POSTR
INSULA ANTR
ORB FRONTAL
TPO
LESION MID
LESION POSTR

22. SEEG DATA IN HYPERMOTOR SEIZURES
• 11 cases HMS - SEEG
• all seizure free post surgery
• SEEG implantation(avg
electrodes)
– frontal - 10
– temporal - 3.5
– insula - 1
– parietal - 1

23. DOES SEEG EVIDENCE OF ICTALACTIVATION OF
SPECIFIC NETWORK CAUSES THE ICTAL SIGNS IN HMS ?
HMS TYPE 1
ORBITOFRONTAL
AMYGDALAR CIRCUIT
ROSTRAL ANT CINGULA
HMS TYPE 2
MESIAL PREMOTOR
DORSAL ANT CINGULA
INSULA/ SMA

24. HMS - FONTAL LOBE SEEG ZONES (RHEIMS et al.,2008)
MOTOR -BA 4
INSULOOPERCULAR
BA 13.14.15.16.43.44.52
DORSOLATERAL PMC
BA 6 & 8 ( LATERALASPECT)
MESIAL PREMOTOR CORTEX
BA 6 & 8 ( MESIALASPECT)
INTERMEDIATE DORSOLATERAL CORTEX ( ILC)
BA- 9,45,46 (LATERALASPECT)
INTERMEDIATE MESIAL FRONTAL ( IMC)
BA 9 ( MESIALASPECT)
FORNTOPOLAR CORTEX BA 10
ORBITOFRONTAL CORTEX BA 11,12
ANTERIOR CINGULATE CORTEX BA 25,24A,24B,32

25. LOGICAL COMPARISON OF RHEIMS &BONINI SEEG DATA
FOR HMS !-
• HMS 1 = BONINI GROUP 4
• HMS 2 = BONINI GROUP 1/2

26. A PRACTICAL SIMPLE PROTOCOL -SEEG
MRI NEGATIVE
HYPOTHESIS/PET ++++MEG/SPECT
EXTENSIVE BILATERAL COVERAGE
MRI POSITIVE [LESIONAL]
LESION [ANT, POST, MID, INF, SUP]
HYPOTHESIS [NETWORKS]

27. TAKE HOME POINTS
• SEEG is safe and less invasive.
• Useful for MR negative DRE, b/l implantations, deep focus, mesial
structures , failed cases, post craniotomy.
• SEEG has defined ictal and interictal patterns
• Case specific implantations based on hypothesis
• Good for functional mapping and extraoperative mapping
• EZ & PNZ relationship can be studied well
• Gives good outcomes if done with proper planning & understanding
• Less time consuming implantations with ROSA or S-8

28. THANK YOU......