Epilepsy Surgery Flashcards
Treatment options for medically refractory epilepsy
- Surgical resection
- VNS
- Multiple subpial transections
- DBS
- OThers: DBS, transgeminal nerve stimulation, external VNS, transcranial direct current stimulation, ketogenic diet
Best predictor of postoperative adequacy
Preoperative cognitive and psychosocial status
-Lower the preoperative cognitive and psychosocial status, the lower the risk of further decline
Intracarotid Amobarbital Procedure (Wada)
Helps lateralize language dominance and memory function
Can lateralize seizure onset (side with poor memory likely seizure onset)
Surgical Outcomes
At 1 year, patient seizure free 58% compared to 8% on medication
People with surgery
Had less CPS and better quality of life
10% had adverse side effects - language and memory related problems
Early Randomized Surgical Epilepsy Trial (ERSET)
Outcomes:
Seizure freedom 11/15 pts in surgical 0/23 in medical group
QOL better in surgical group
Memory decline in 36% of pts after surgery
Adverse events: stroke - surgical case. 3 with status in medical group
Resective surgery +ASM in patients with new refractory MTLE results in lower probability of seizures in second year
Surgical Methods
Temporal lobe surgery Lobectomy Resection of epileptogenic zone Lesionectomy Corpus Callosotomy Hemispherectomy Multiple subpial transection
Different Methods for temporal lobectomy
Standard (en bloc) anterior temporal lobectomy (ATL) - 3-6 cm of anterior temporal neocortex + 1-3 cm of MTS (amygdala + hippocampus)
Modified + limited neocortical resection = 3.5cm from temporal pole sparing superior temporal gyrus (avoid language deficits)
Selective amygdalohippocampectomy
Stereotactic radiosurgery
Standard Amygdalohippocampectomy
Attempts to preserve lateral temporal cortex out of concern for language deficits
- Resect up to 4-4.5 cm on dominant
- Resect u up to 6-6.5cm on nondominant
- Preserves the neocortical areas
Outcomes following Temporal lobe surgery
seizure free rates:
At 12 months - 82%
At 24 months 76%
At 63 months - 64%
Complete or better seizure outcome was associated with significantly better QOL
Risk factor for seizure recurrence was reduction in ASM
Standard Anterior Temporal Lobectomy OUtcomes
Seizure freedom 89%
Engel Class I or II - 94%
*Highest concordance was with video EEG > PET> MRI > Wada > SPECT/Neuropsych
Inferior Temporal approach to Standard Anterior Temporal Lobectomy
safe and effective with low morbidity and mortality.
Complications: delayed SDH, wound infections, delayed ICH, small lacunar stroke, one transient frontalis nerve palsy
Selective Amygdalohippocampectomy (SAH)
Aim: Minimize neurocognitive side effects of temporal lobectomy
Result: Some improved, some no clear benefit or event significant verbal memory deficits (in dominant SAH)
Risk of Neurocognitive Deficits and Risk factors following ATL
Larger temporal lobe resection associated with better seizure control, but also high risk of cognitive outcome
> 2 cm for mesial
4cm for neocortical
Standard vs Selective Temporal Lobe Surgery
ATL is more likely to achieve Engel Class I outcome compared to SAH
Thus, standard ATL confers better chance of seizure freedom
Comparison of right vs left temporal lobectomy
Post-operative after Left temporal lobectomy:
- Verbal memory decline
- Performance intellegence decline
Post-operative after RTL:
-visuospatial memory outcome
More resection is associated with worse functioning
Outcome following nonlesional partial epilepsy surgery
Engel Class I 81% at 6mo 78% at 1 year 76% at 2 years 74% at 5 years 72% at 10 years
Positive Predictors for outcome for nonlesional epilepsy surgery
Seizure control at 1 year –> 92% prob of remission at 10 years
Negative Predictors for nonlesional epilepsy surgery
Extratemporal seizure focus
Previous surgery
Male gender
Normal tissue pathology
Outcome following ATL in Nonlesional TLE
Complete seizure freedom rates:
1 year 76%
2 years 66%
7 years 47%
*Memory decline reported with dominant hippocampus resection
Negative predictors (risk factors) for outcome of nonlesional TLE surgery
Higher baseline seizure frequency
Preoperative GTCs
Outcome following Frontal Lobe Surgery
Patients with identifiable lesion more likely to achieve seizure freedom than those with poorly localized lesion
Engel class I outcome 45.1%
Predictors for long term seizure freedom in FLE
Lesional origin
Abnormal MRI
Localized frontal resection (vs extensive lobectomy)
Earlier seizure resection in FLE
Risk factors for lack of seizure freedom in FLE
Left frontal lobe epilepsy surgery
Dominant hemisphere
Patients without aura
Interictal epileptiform discharges in scalp
Intracranial EEG widespread >2 cm) in contracst to focal seizure onset
Shorter latency to onset of seizure spread
Ictal involvement beyond frontal lobe
*Lack of seizure freedom is likely because of widespread epileptogenicity
Supplementary Motor Area Seizures
Semiology
EEG
Tonic posturing of extremities, usually bilateral
“Fencer posturing”
Usually retained awareness
Usually epileptogenic zone is outside of SMA with rapid spread to SMA
EEG: ictal, interictal EEG often unrevealing.
SMA Surgery approach
If seizure outside of SMA -> resection of epileptogenic zone, leaving SMA intact
Resect SMA while sparing primary motor cortex –> can result in >90% seizure reduction
SMA resection side effects
Transient paresis or severe defciit without permanent loss of motor or speech functions (usually 24hrs)
Favorable outcome is common
Multiple subpial transection (MST)
Used in:
Introduced to spare eloquent cortex in patients in where epileptogenic zone lies in eloquent cortex
Also used in LKS
MST outcomes
MST + resection = MST alone
>95% seizure reduction compared in >95% in MST alone
Overall Seizure-Free Outcome
Temporal Lobectomy 55-80% Frontal lobe resection 5-18% Frontal Lobectomy 23-68% Parietal Lobe resections 45% Occipital Resections 44-88% Hemispherictomy 60%
Long term outcome (>5 years) Seizure Free
Temporal Lobe resections 66% Occipital and parietal resections 46% Frontal lobe resections 27% Multiple subpial transections 16% Callosotomy 35% (from most disabling seizures)
Failed Epilepsy Surgery and Reoperation
Seizure freedom reported 36.6%
Complications rate at 13.5%
Parietal Lobe epilepsy
Semiology
Auras (94%) -somatosensory (pain, dysesthesias), vertigo, aphasia, disturbances with ones own body image
Ictal propagation to SMA -> hypermotor manifestations
Ictal propagation to temporo-limbic regions -> complex visual or auditory hallucinations and automatism
Given propagation, semiology is less of value
Parietal lobe seizures EEG
Variable scatter of interictal discharges
Less localizing ictal EEG
HFO helpful in seizure
Parietal lobe surgery SE and outcome
Postoperative sensory deficits - temporary partial hemisensory or Gerstmann syndrome when corticetomy involves post-central gyrus
Outcome: complete or nearly seizure freedom 65-67.5% favorable outcome
Parietal lobe epilepsy pathologies
low grade tumors
Cortical dysplasia
Gliotic scars
Cavernous vascular malformations
Occipital lobe epilepsy
Seizure semiology
Auras reported in 88% of patients
- Elementary visual hallucinations, ictal amaurosis, eyemovement sensations, early forced eye blinking or eye lid flutter, contralateral visual field deficits
- Often head, eye deviation (often contralat)
- LOC
- Various automatisms, fumbling, asymmetric tonic or focal clonic motor
Medial/lobar lesions - more likely to cause VF defects
Occipital lobe EEG
scalp EEG rarely localizing
Intracranial EEG correctly localizes seizure origin
Occipital lobe epilepsy resection outcome
46-88% seizure freedome
Most common pathologies - dysplasia, tumors, gliosis
Following resection - ~50% will not experience any new VF deficits
Insular-Opercular Seizures
Nocturnal-Complex motor seizures
Auras include:
Vicerosensitive or somatosensory symptoms.
Ictal Semiology: asymmetric tonic-dystonic posturing, hyperkinetic autosmatisms (bimanual, bipedal activity and ballistic movements)
Insular-Opercular Seizures on EEG
Simultaneous insular and opercular ictal discharges are present
Complex motor manifestation –> when spreads to frontomesial regions (cingulum, superior frontal gyrus, SMA) and/or mesial/neocortical temporal lobe structures
Outcome of insular-opercular Surgical outcomes
Insular opercular cortical resections have favorable outcome
Usually pathology: dysplasia
Epilepsy Surgery in Children
49% seizure freedom
13% experience >75% seizure reduction
Cognitive outcomes 76% followed their expected cognitive trajectory
HFO and Epilepsy in Children
Intracranial EEG demonstrated high prevalence of ictal HFOs zones in 93% of patients
Complete resection of ictal HFO is highly associated with favorable surgical outcome
-Complete seizure freedom 82% in complete HFO resection vs 21% after incomplete resection
Complications of Depth Electrodes
Asymptomatic subdural bleeding gliosis, degeneration, microabscesses along electrode tract
0.5-5%
Complications of Sub dural electrodes
Infection Transient neurologic deficits Epidural hematoma Increased intracranial pressure Infarction Death 0.5% CSF leak
More likely to have complications if >60 electrodes and if grids left in >10 days
Risks: Older patients, left sided placement, additonal burr holes
Engel Class Definitions
Class I = seizure free with no aura beginning one month after surgery
Class II = patients with auras only
Class III = patient with 1-3 seizures per year
Class 4 = patients with seizures ranging from 4/year to 50% decreased days with seizures
Class 5= Patients with 50% reduction to 100% increase in days with seizures.
Class 6 = patients with > 100% increase
Classes 3-6 include patients with or without auras
Memory and Post operative Epilepsy Surgery
Can be worse when
- Dominant hemisphere temporal lobe resection
- MRI does not show excluse unilateral MTS
- Preoperative immediate and delayed recall memory is intact
Specifically decline in object naming
Memory in post-operative epilepsy surgery can improve
Nondominant resection is performed
Adverse effects of TLE surgery
Quadrantanopsia/Visual field deficits --> 2-4% with hemianopsia Memory problems Hemiparesis (2.4%) Anterior choroidal artery or other occlusions/strokes Cerebellar hemorrages Infection Epidural Hematomia Transient 3rd ner ve palsy 20% transient anomia 1-3% dysphagia 2-20% transient psychosis or depression
Death is 0.24% of pateints
Acute Disconnection Syndrome
Akinetic mutism
Incontinence
Apraxia
Alien hand syndrome
This is though to be due when entire CC sectioned initally –> most like to do anterior 2/3 section first
MEG and TLE
Where are the dipoles?
Mesial = anterior temporal horizontal anterior posterior dipoles
Anterior temporal = vertical dipoles
Lateral = posterior temporal vertical dipoles
