Epilepsy Surgery Flashcards
Factors that suggest good postsurgical outcomes
- Later age at onset
- Shorter duration of epilepsy
- presence of febrile seizures
- Positive MRI or PET
- Unilateral findings on PET
- Concordant data (between MRI/PET/EEG)
- lack of need for intracranial monitoring
MRI sequence best to identify subtle features of temporal lobes (MTS, incomplete hippocampal inversion)
Oblique coronal
Criteria for MTS
Main (3)
Other features you may see (5
Main
- hippocampal atrophy
- increased T2 signal
- abnormal morphology or loss of internal architecture of hippocampus
Secondary features
- dilation of temporal horn of lateral ventricle
- Loss of gray-white matter differentiation in the temporal lobe
- decreased white matter in the adjacent temporal lobe
- atrophy of ipsilateral forinx
- atrophy of mamillary body
% of MTS cases that are bilateral
10%
What 3 things do you see in this picture?
- Enlargement of left lateral ventricle temporal horn
- left hippocampus smaller and hyperintense compared to contralateral side
- Left hippocampus is abnormally smooth
What 3 things do you see in this picture
Left hippocampal volume loss
- Hyperintense hippocampus
- subtle laminar blurring
What sequence is this?
What is this showing?
- T2-waited image
- globular let hippocampus
What sequence is this?
What is the arrow showing? (1+2
-T2-weighted image
Showing incomplete hippocampal inversion
- More vertical left collateral sulcus
- Low-lying left body of the fornyx
What sequence is this?
What is this showing?
- Coronal Flair
- FLAIR hyperintensity in bilateral MTS
What is this sequence?
What is this showing?
T2 waited
- laminar blurring bilateral MTS
What is this sequence?
What is this showing? (2)
Coronal T2
Right volume loss and laminar blurring (Right MTS and right fornix atrophy)
What is this Sequence?
What is this showing?
- 3D T1-weighted image
- volume loss in bilateral MTS
What are these sequences?
What is this showing?
Small Gray matter heterotopia on T2-weighted(B), but better seen on Coronal double-inversion (C) and T1 (D)
What are these sequences?
What are they showing?
Axial + coronal T2 (A+B), Coronal Flair (C)
small emphalocele in fusiform gyrus extending to right foramen ovale
What is this sequence
What is this showing (2)
Coronal FLAIR
- gray-white Blurring
- FLAIR hyperintensity in left frontal anterior cingulate gyrus (FCD)
What is this sequence
What is this showing (2)
Axial FLAIR sequences
- gray-white Blurring
FLAIR hyperintensity in left medial frontal gyrus (FCD)
What are these sequences?
what do they show?
- T1-weighted (A) and Axial FLAIR (B)
- Pachygyria
What are these sequences? (2)
What are they showing?
- Coronal and axial FLAIR
- thickened cortex in right posterior sylvian fissure (Polymicrogyria)
What are these sequences? (2)
What are they showing?
- Sagittal and axial post-contrast T1
- Thickened cortex extending from right sylvian fissure toward vertex (Polymicrogyria)
What are these sequences?
What are they showing
Coronal / Axial FLAIR (A,B) and Sagittal/Axial Post-contrast T1 (CD)
- thickened cortex in right posterior sylvian fissure, extending to vertex (Polymicrogyria)
Symptoms of a common side effect syndrome following :
ANTERIOR corpus callosotomy (3)
POSTERIOR Corpus Callsotomy (2)
TOTAL callostomy (4)
Anterior disconnection syndrome
- Mutism
- left leg paresis
- urge urinary incontinence
Posterior acute disconnection syndrome
- tactile transfer deficits
- visual transfer defects
TOTAL / near total resection: Split brain syndrome
- language impairment
- disordered attention
- disordered memory sequencing
- hemisphere competition
What type of electrodes are best used to detect DC shift?
What is the best Time constant?
What type of impedence?
Platinum electrodes
long time constant
High impedence
What is included in a “standard” anterior temporal lobectomy (4 + one omitted)
- amygdala
- hippocampus
- parahippocampal gyrus
- 3.5-4 cm of lateral temporal neocortex
NOT resected: - Superior temporal gyrus
what is included in a selective amygadlo-hippocampectomy (3 + omitted)
- amygdala
- hippocampus
- limited resection of parahippocampal gyrus
NOT resected: - temporal neocortex
In standard anterior temporal lobectomy, how much of the lateral temporal neocortex is resected, and why?
3.5-4 cm of lateral temporal neocortex
- minimizes verbal memory
In standard anterior temporal lobectomy, why do we not resect the superior temporal gyrus?
minimizes naming difficulties after dominant resections.
factors associated with HIGHER rates of post-operative seizures following resection
- widespread (>2cm) ictal onset pattern
- short latency to onset of seizure
- failure to resect tissue
factors associated with LOWER rates of post-operative seizures following resection (2)
- beta-to-gamma-range activity at seizure onset
- resesction of tissue that shows discharges in the first 3 seconds after onset (best one)
Frontal lobectomy statistics:
- probability of complete seizure freedom at
1 year
3 years
5 years
If seizures are going to recur, when are they most likely to?
1 year: 56%
3 years: 45%
5 years: 30%
80% of seizure recurrences occur within first 6 months
Frontal lobectomy Statistics:
Independent risk factors for seizure recurrence (5)
- Causative focus is MRI-negative
- Any extrafrontal MRI abnormality
- Generalized / nonlocalized ictal EEG patterns
- occurrence of postoperative sizures
- incomplete surgical resection
Requirements for capturing HFO’s (3)
- Sampling rate of at least 1000 Hz
- LFF > 50 Hz
- HFF > 600 Hz
HFO’s: Criteria for:
Ripples:
Fast ripples:
Ripples: 80-200Hz
Fast ripples: 250-500Hz
Percentage of patients who will be free of disabling seizures after:
- anteromedial temporal resection
- neocortical resection
- 2/3
- 1/2
What “non-discharge” feature, when present at ictal onset, can be a predictor of a favorable surgical outcome?
beta activity at ictal onset
Percentage of patients with bilateral language:
- left handed
- Right handed
Left handed: 0-38%
Right-handed: 0-30%
Lesion at or before what age increases likelihood of bilateral language
6 years
patient with bilateral language has Wada. What are two possible reactions to look for?
Prolonged speech arrest after injection (“bilateral dependent”) or no speech arrest after either injection (“bilateral autonomous”)
vessel most commonly injured during anteromedial temporal resection and common effect
- Anterior choroidal artery
- hemiparesis
Sensitivity and specificity of SPECT with TLE
Ictal
Postictal (2)
Interictal (2)
Ictal
- Sensitivity: 75-95% (similar temporal and extratemporal)
- Specificity 70-100% (Similar in temporal and extratemporal
Postictal
- TLE: 75% (slightly lower) and 1.5% false-positive
Interictal
- Sensitivity: 44%
- False-positive rate 7.5%
Where is Subtraction ictal SPECT co-registered to MRI (SISCOM) most used in epilepsy surgery?
in Extratemporal epilepsy, presence of a SISCOM focus that is subsequently resected has better probability for postsurgical seizure control than when it is unresected or absent (58% vs 18%)
Likelihood of favorable postoperative outcome in FCD
50-60%
Patient with focal epilepsy has this MRI, what does he have?
L Temporal FCD
types of resections that can actually improve the following:
- Verbal memory
- visuospatial
Verbal memory
- Can improve after nondominant temporal lobectomy
Visuospacial memory
- Can improve following dominant temporal lobectomy
what 4 neuropsych tests are most helpful in assessing coexisting frontal lobe testing in patient with TLE (and what do they test)
Stroop Color Word Test (tests attention)
Wisconsin Card Sorting Test (problem Solving)
Animal Fluency test (language)
Grooved Pegboard test (motor speed)
Risk of intracerebral hemorrhage with Depth electrode placement
1-4%
cortical stimulation:
- biphasic or monophasic?
- longer or shorter trains for language cortex
- longer or shorter for motor cortex
- biphasic
- longer trains for language cortex
- shorter for motor cortex
