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Epilepsy
Rik Achten, MDDepartment of Neuroradiology,
Ghent University Hospital Ghent Belgium, GIfMI, Ghent University, Ghent, Belgium
Ruben De Rouck, master thesis 2014-2015Promoter: R. Achten
Epilepsy referrals Ghent University Hospital (GUH)
● Period: 1990 till 2/2014● RIS survey
● (“MR*” and “hersenen” and (“Epilep*” or “TLE” or “CPE”))
● Returned 8461 reports● 6998 high quality reports after exclusion of non-MRI
reports, MRS, fMRI, expert reviews, incomplete reports (neuronavigation, electrodes, incomplete exams)
● 5794 unique patients● Reports where manually analysed and tagged with
categories describing clinical information, and whether patient was in for epilepsy surgery
Classification of epilepsy-associated findings on MRI
Classification of epilepsy-associated findings on MRI NLP Pipeline
A set of binary classifiers was trained to detectthe precense of abnormalities
Ordinal classification of lesionepileptogenicity Age, sex and MRI field strength
Age distribution of findings EpidemiologyMost recent MRI as reference
Group Count % of lesions % of total
Hippocampal Sclerosis 257 13,80% 4,44%
Mesial Temporal Sclerosis 65 3,49% 1,12%
Malformations of cortical development 149 8,00% 2,57%
Other developmental 40 2,15% 0,69%
Vascular malformations 155 8,32% 2,68%
Tumor 293 16,79% 5,06%
Genetic syndromes 37 2,12% 0,64%
Encephalomalacia 538 30,83% 9,29%
Cerebrovascular 282 16,16% 4,87%
Other (metabolic, hemorrh.,perinatal, infectious)
249 14,27% 4,29%
Unspecified 151 8,56% 2,61%
Difference in 3T detection rateMost recent MRI as reference
New findings on 3T scan
304 patients had 1.5T scans followed by 3T scansSignificantly more epileptigenic lesions wherefound on 3T (Wilcox on signed rank test, p < 0.001)Contributors:
Encephalamalacia (weak indicator)Hippocampal sclerosis (strong indicator)Malformations of cortical development (strong as well)
Lesion types found Need for optimized protocols ?Von Oertzen et al. (2002), JNNP
Optimized protocol @ GUH @ 3 T
6'24”
6'39”
5'12”
5'12”
1'
3'
SWI 3'12”
Sequence Resolution Acquisitiontime Use
Sagittal 3DMPRAGE 0,9 isotropic Anatomical detail3D cortex evaluation
Sagittal 3DFLAIR 0,9 isotropicGliotic changes, changes
in myelination, inflammation,edema
Coronal high resolution T2Wperpendicular to HC
slice 3 mmin plane 0,4 mm
Details of HC structureTL integrity
Axial high resolution T2WACPC
slice 3 mmin plane 0,4 mm
T2W anatomical detailoutside TL
Axial DWI 3 mm slicein plane 1,5 mm
Cytotoxic edemaDetails cystic content
Axial T2*W 3 mm slicein plane 0,8 mm
HemosiderineIon deposits
3 mm slicein plane 0,7 mm
Venous anatomyFe and other ion depositsSWI 3'12”3 mm slice
in plane 0,7 mmVenous anatomy
Fe and other ion deposits
Viewing StrategyFLAIR (3 plane reconstructions or 2D cor and ax):
Signal anomaliesFollow any lead, white matter lesions or gray matter?
Coronal T2, FLAIR, T1:Hippocampal sclerosis (HS)?Wall ventricle: heterotopia, smooth edges? (follow any lead to cortex), periventricular white matter?
3 D T1 High Res (3 planes, avoiding partial volume):Cortex: edges with white matter (blurring), cortical thickness, polymicrogyria (PMG)
GE T2, T2* or SWI:Hemosiderin depositions (DAI)Small cavernoma and other vascular anomalies
Subiculum
CA2
CA3CA4
CA1
Alveus
Dentategyrus
Incomplete hippocampal inversion
Atypical anatomical pattern of the hippocampusRounded shape and blurred internal architectureMostly in the left HC (17% versus 6%)Associated with morphological abnormalities outside the temporal lobe, mainly in the limbic lobe
C. Curry et al. Front Neuroanat 2015 22:160 (2000 subjects from normal population)
Associated with prolonged febrile seizures (PFS)?8,8% of PFS patients versus 2,1% of control subjects
S. Chan et al. AJNR 2015 205:1068
Incomplete hippocampal inversion Optimal MRI for TLE: HCS
● CPE– patient with complex
partial epileptic seizures originating in the right hemisphere
– semiology = TLE– Typical image of HCS
on the coronal MRI images (3T)
– PO: Engel IA
Patient with left TLE: HS+
● HS with high signal T2 (FLAIR) and low signal T1 hippocampus
● Left hippocampus is atrophic
● Atrophy of left anterior temporal lobe, high signal white matter, blurring
Patient with left TLE
Minimal HC damage: only structural change
New insights from ILAEBlümcke et al; Epilepsia 2013
HCS is classified in 4 categories resulting fromrecent studies showing that this is probably usefulin respect to ethiology and prognosis1. HCS type 1: neuronal cell loss and gliosis in CA1 and CA4
regionsEarly damage (<5yrs) and more favorable outcome aftersurgery
2. HCS type 2: neuronal cell loss and gliosis in CA1 region3. HCS type 3: neuronal cell loss and gliosis in CA4 region
Type 2 and 3 less well studied, but probably later onsetand less favourable outcome
4. No-HCS: only gliosis, no cell loss.
Proton MR spectroscopy Proton MR spectroscopie
Generalized Epilepsy and MRS
● Patient, male, 1979– primary generalized epilepsy, with daily absences,
facial clonic movements– mental retardation, left handed, analphabetic– brain MRI normal– video-EEG: compatible with Lennox-Gastaut syndrome– AED's without much succes– VNS in 2004: no change– IVIG: no change– 2007, situation deteriorates at home– MRS (no anesthesia)
Generalized Epilepsy and MRS
Generalized Epilepsy and MRS Malformations of cortical development
● Often associated with seizures● Also associated with other symptoms or
presentation: behavioral problems, mentalretardation, developmental delay...
● Types:● Neuronal proliferation● Neuronal migration● Cortical organization
● Classification by Barkovich et al. Neurology 2001
Focal cortical dysplasias: new ILEA classification 2011
Cortical dysplasia with balloon cellsFocal Cortical Dysplasia Type IIb
Cortical dysplasia with balloon cellsFocal Cortical Dysplasia Taylor Type II Heterotopia
Polymicrogyria Mass lesions: DNET
Presurgical risk estimation
● Neurosurgeons and neuro-interventional radiologists rely more and more on imaging to assess the possible risks for their procedures
● Standard state of the art structural imaging can narrow the differential diagnosis and gives accurate anatomical information
● Perfusion gives physiological information● DTI/DSI provides information on major white matter
tracts● MRS helps define the most metabolic active region in a
tumor● fMRI is solicited for functional information on brain at risk
The Wada test (IAP-IAT)
●
●
●
est (IAP IAT)
Appropriate choice of fMRI paradigm for correlation between fMRI and IAP
● Procedures for fMRI language used in Ghent, Belgium, easily performed in patient population
– Expressive language● Verbal fluency with visual cue: classical UNKA test
– Receptive language (less lateralizing)● Semantic categorization task: classify visually presented
words as animal or object > classify letter strings as capital or not (performance control: button presses)
● Reading task: reading visually presented meaningful text > reading nonsense text
– Calculation of lateralization index● at which T-value?● TDLC (threshold dependent laterality curves)
fMRI vs WADA: language
fMRI vs WADA: language fMRI of language
● Combining 3 language tasks: language network
fMRI vs WADA: memory
● Paradigm 2: encoding of Snodgrass line drawings
Memory fMRI in epilepsy
● TLE Patient SI● Man, age 39 yrs● No abnormalities on MRI● Depth EEG shows focal
beginning of epilepsy in right TL
● WADA – memory left: 9/11– memory right: 5/11
● fMRI– lateralization index:
0.59
Future(and oddeties)
Seizure fMRIMEG combined with SFC structural MRIConnectomicsSimultaneous EEG and fMRI…
NMR: seizure fMRI
Patient with SPS10 yr old boy with frequent SPS (epigastric sensation
and autonomic symptomsHad previous surgery for astrocytoma (WHO II) in the
left TL, resection was incompleteSeizure fMRI
Positioned in the magnet with clinical monitoringEPI volume head scanning for 1 hourLate in the scan periode the patient experiences a SPSData are send to workstation and a regressor is build for
SPM
NMR: seizure fMRI Magneto-encefalografie: MEG
Surface coil MRI MEG guided SCF MRISamuel Lapere & Evelien Carrette GIfMI
Epilepsy as a brain networkdisorder (ILEA)
Resting state functional connectivity
● Look in the brain for regions with similar BOLD signal fluctuations
Maccotta et al. Impaired and facilitated functional networks in temporal lobe
epilepsy. NI Clinical 2013.
● Significant functional decoupling across hemispheres that affects both medial and lateral/neocortical temporal regions.
● Increased correlations in the temporal region ipsilateral to the seizure focus, especially involving the insula.
● Legend: HH: hippocampal head, HB: hippocampal body, P: parahippocampus, F: fusiform gyrus, IT: inferior temporal gyrus, MT: middle temporal gyrus, ST: superior temporal gyrus, I: insula, A: amygdala.
Simultaneous EEG and fMRI
Gradient noisecurrents induced in the EEG leads by gradient switching
are typically 100 to 1000 times geater in amplitude than the EEG signal but have repetitive nature with known timing
removal relies on accurate recording of the artifact which requires high frequency sampling of EEG, large buffers, precise timing, etc...
Simultaneous EEG and fMRI
Imaging in epilepsyTake home points
Use MRIUse optimized imaging protocols for diagnosisTalk to the cliniciansBecome an expert readerMRS in selected casesfMRI (and DTI) for epilepsy surgery risk estimationMore advanced & research
Multimodality with structural MRI combined with EEG, MEG, fMRI, DTI, PET, …
Thank you
Brain Power