Epilepsy Surgery American Epilepsy Society
Epilepsy Care Seizure Epilepsy diagnosis Medication trials Imaging for pathology Medical intractability Surgical Consideration Surgical workup Surgery
Candidates for Epilepsy Surgery Persistent seizures despite appropriate pharmacological treatment Usually at least two drugs, appropriate to seizure type, at adequate doses, with adequate compliance Impairment of quality of life due to ongoing seizures Loss of driving privileges, employment opportunities, social/cultural stigma, dependence on others, side effects of medications, under achievement in school, memory deficit, attention deficit, injuries, accidents
Presurgical Evaluation • History and Physical Exam • Electroencephalography • Imaging • Presurgical Testing • Neuropsychology Evaluation • Comprehensive Patient Care Conference
Imaging for Surgical Candidates MRI- with epilepsy protocols • T1- inversion prepared, gradient-echo, echoplanar, true inversion recovery image • T-2- fast spin echo, FLAIR, 3D volume acquisition
Presurgical Evaluation- MRI Right hippocampal sclerosis (arrow)
Presurgical Evaluation- MRI Left mesial temporal sclerosis
Presurgical Evaluation- PET/SPECT Functional Imaging • PET • hypometabolism interictally • SPECT • hypoperfusion interictally • hyperperfusion ictally • PET and/or SPECT may be coregistered with MRI
Presurgical Evaluation- SISCOM SISCOM (SPECT with MRI coregistration) in a patient with extratemporal epilepsy
Presurgical evaluation - fMRI fMRI- language lateralization, hippocampus function, epileptogenic focus assessment Patient with left temporal lobe epilepsy. Left: Language mapping with verb generation task - activation in Broca’s and Wernicke’s areas. Right: Memory localization with picture encoding task - decreased activation in the left hippocampus.
Presurgical Evaluation- MEG • Magnetoencephalography (MEG) • Magnetic source localization of interictal epileptiform discharges • Functional mapping • fMRI has a good spatial resolution but provides poor temporal correlation, while EEG provides timed waveforms with poor localization. MEG jointly records these two signals providing spatially and temporally correlated images.
Testing for Surgical Candidates Visual fields Formal testing if resection will endanger vision Intracarotid Amobarbital Procedure (Wada) Language dominance Verbal memory Prediction of postoperative decline Phase II monitoring with intracranial electrodes if necessary Subdural/depth electrodes Identification of ictal onset and epileptogenic zone Allows for cortical mapping if needed Cortical mapping Intraoperative (phase III) or during phase II monitoring Identification of eloquent areas of cortex
Neuropsychological Evaluationfor Surgical Candidates Provides preoperative baseline Predicts risk of cognitive decline with surgery Testing includes: IQ battery of tests Language localization Memory- verbal and visual localization Visuospatial function Attention/Executive Motor- coordination and speed Psych- expectations of surgery, coping skills, social support, stability
Comprehensive Patient Care Conference for Surgical Candidates • Epileptologist presents the patient • Video-EEG studies are reviewed • Semiology • Interictal EEG morphology • Ictal EEG morphology • Neuroradiologist discusses imaging studies • Neuropsychology results are examined • Neurosurgeon delineates surgical options • Discussion of risks/benefits/outcomes • Group consensus
Epilepsy Surgery Phase II subdural electrodes for intracranial monitoring
Types of Surgical Procedures • Resective Surgery: • Lesionectomy • Selective amygdalohippocampectomy • Corticectomy • Lobectomy (e.g. temporal lobectomy) • Multilobar resection
Types of Surgical Procedures • Disconnective/Palliative Surgery: • Hemispherectomy • Anatomic • Functional • Corpus Callosotomy • Multiple Subpial Transections • Vagus Nerve Stimulator
Surgical Treatment of Epilepsy MRI frameless stereotactic localization of focal cortical dysplasia at the base of the central sulcus (center of cross hairs)
Standard Temporal Lobectomy 4.5 cm Resection of the anterior temporal lobe (~4.5 cm on left side, ~5.5 cm on right side) followed by resection of mesial structures (amygdala, hippocampus, parahippocampal gyrus)
Selective Amygdalohippocampectomy • Idea is to remove mesial structures (hippocampus, amygdala, parahippocampal gyrus) leaving lateral temporal cortex intact • Distinct surgical approaches include: • Transsylvian • Transcortical • Subtemporal
Functional hemispherectomy Introduced by Rasmussen Extensive cortical resection in temporal and central cortex with disconnection of residual frontal and occipital cortex by transecting white matter fibers (not shown) Transsylvian Keyhole Perisylvian Deafferentation Classic (Rasmussen)
R hemimegalencephaly in a 7-month-old boy Pre-op Post-op
Transsylvian functional hemispherotomy (Schramm) Transsylvian exposure and temporomesial resection (uncoamygdalohippocampectomy) Transventricular callosotomy and occipitoparietal mesial disconnection Frontobasal disconnection
Corpus Callosotomy corpus callosum Introduced by William P. Van Wagenen in 1940 For intractable generalized epilepsy Particularly effective against “drop attacks” Partial vs. complete Spares the anterior commissure, fornix pericallosal artery septum pellucidum callosotomy (in progress)
VNS Surgery Electrodes are placed around the left vagus nerve and connected to the pulse generator in the chest or abdomen
Clinical Trials Experimental Surgical Treatments Under Clinical Trials • Deep brain stimulation • Responsive neurostimulation • Gamma knife radiosurgery
Head Trauma and Epilepsy • Acute symptomatic seizures • Usually within few days after head trauma • Incidence is proportional to the severity of trauma • Remote symptomatic seizures • Seizure prevention in patients with traumatic brain injury
Risk Factors for Epilepsy Risk ratio LVH = left ventricular hypertrophy. *Protective. Hesdorffer DC, Verity CM. In: Engel J Jr, Pedley TA, eds. Epilepsy: A Comprehensive Textbook; vol 1. Philadelphia, Pa: Lippincott-Raven Publishers; 1997:59-67.
Head Trauma and Epilepsy 404 pts, severe head injury with cortical damage randomized in < 24 hr: phenytoin vs. placebo. Seizures in one week: placebo 14%, phenytoin 4% Once late seizure occurs, 86% recurrence. Recommend: Use prophylactic AED for 1-2 weeks after severe head trauma, then stop. If late seizures occur, treat with AED. Temkin, NEJM 1990.
Conclusion • Many patients with medically-intractable epilepsy are surgical candidates • All patients with epilepsy should undergo epilepsy protocol imaging • Many modern epilepsy surgery options exist, including resection, disconnection and palliation