Epilepsy Surgery Flashcards
What is the irritative zone.
Interictal spikes on the EEG or MEG
What is the symptomatic zone?
The area of cortex that, when activated by an epileptic discharge, reproduces the patient’s typical clinical symptoms.
What is the ictal onset zone?
The area of cortex from which seizures can be objectively demonstrated to arise.
What is the functional deficit zone?
The area that shows abnormal functioning during the inter ictal period and can be identified by clinical examination, functional neuroimaging, the WADA test, neuropsychology, etc
What is the epileptogenic zone?
The area of cortex that is able to generate seizure and whose complete removal results in seizure freedom.
What is the advantage of subdural grids over depth electrodes?
Ability to record functional information.
Why is the combination of EEG and fMRI useful for investigation of the epileptic focus?
It is a noninvasive means of investigating the whole brain.
What is required for EEG-fMRI to investigate the epileptic focus?
As long as epileptic discharge is present in scalp EEG.
What is the mechanism of how EEG-fMRI works?
The method examines metabolic changes at the time of interictal activity, not at the time of seizures.
What is the major complications of extratemporal epilepsy?
Hemiparesis, major visual field defects, and dysarthria
What is the percentage of major complications in extratemporal epilepsy surgery?
6.5%
What is the percentage of minor complications in extratemporal epilepsy surgery?
12%
What are the common minor complications of extratemporal epilepsy surgery?
Visual defects, hemiparesis, and dysphasia
What is the seizure-freedom rate after epilepsy surgery what percentage of patients?
30%
What supplementary tests can increase success rate of seizure freedom when results are concordant with EEG findings?
PET, SISCOM, and intracranial recordings.
What is SISCOM?
Subtraction ictal single photon emission computed tomography
How do FDG-PET and SPECT improve surgical outcomes?
Detection of subtle structural alterations
SISCOM has its best utility in what type of epilepsy?
Extratemporal lobe epilepsy
What is a major complication of hemispherectomy?
23% require shunting
What are the risk factors for possible shunting after hemispherectomy?
Prior brain surgery and anatomical as opposed to functional
What is the percentage of shunts placed after 90 days?
27%
What is the complication of death after hemispherectomy?
Less than 3%
What is the percentage that remain ambulatory?
Greater than 80% of patients who previously walked
How often do seizures arise from the opposite side from the hemisphectomy side?
Up to 30% in patients who had meningoencepalitis, trauma, or cortical dysplasia and in 10% in other etiologies. In about 5% of pets with bacterial meningitis
Can magnetic source imaging (MSI or MEG) can be helpful for surgical planning?
10-15% of cases
What are factors improve outcomes in stereotactic radio surgery for AVMs?
Small AVM size (<3 cm) , presenting with generalized tonic clinic seizures and epilepsy duration less than 6 months
What is a poor prognostic factor for radioablation surgery with patients with AVMs?
Setting of hemorrhage
In seizures from medial temporal lobe seizure onset is seen earlier with hippocampal depth electrodes or subdural strips?
Depth electrodes
What are the advantages of stereo-EEG
Sampling EEG over larger networks but disadvantage of sampling large cortical areas
What are the most common defects after dominant temporal lobe surgery?
Verbal memory deficits and confrontation naming deficits
Surgical intervention thru the middle temporal gyrus or Sylvan fissure may cause fewer naming defects
Surgery thru the middle temporal gyrus may cause less naming defects.
After a dominant temporal resection, usually impairment of verbal memory and difficulty with confrontation naming occurs, can some patients have a different outcome?
Yes, some may not have memory decline
In non-dominant temporal lobe resection, what is the usual loss?
Facial recognition, especially famous faces
MEG/MSI can adequately lateralization what function?
Language in 10-15% , but not memory
What can be the benefits of early surgery in refractory focal seizures?
Reorganization of language and motor function
In patients with bilateral temporal lobe seizures, is it possible to have a good seizure-free outcome with surgery?
Yes, if >80% of seizures arise from one side
Can epilepsy surgery be performed if eloquent cortex is involved?
Yes
What is the most frequent complication in a temporal lobe resection?
Visual field defect
In LGS, what is the percentage of seizure freedom of drop attacks after corpus callosotomy?
As high as 80%
What is disconnection syndrome?
Cognitive impairment due to loss of crossing fibers. Usually less 20% after cc.
