Surgery-epilepsy-introducefrom-ncbi

Epilepsy Surgery American Epilepsy Society

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Candidates for Epilepsy Surgery  Persistent seizures despite appropriate pharmacological treatment (usually at least two drugs at limits of tolerability)  Impairment of quality of life due to ongoing seizures

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Presurgical Evaluation  History and exam  MRI scan • Mesial Temporal Sclerosis (MTS), tumor, vascular malformation, dysplasia

 Video/EEG monitoring with scalp EEG • interictal epileptiform discharges • ictal

– Seizure semiology – Ictal EEG discharge • Additional electrodes S-Slide 3

Presurgical Evaluation Right hippocampal sclerosis (arrow)

Figure 1a

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Presurgical Evaluation Left mesial temporal sclerosis

Figure 1b                      

  Figure 1c

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Presurgical Evaluation  Functional Imaging • PET

– hypometabolism interictally • SPECT

– hypoperfusion interictally – hyperperfusion ictally – subtraction and co-registration with MRI

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Presurgical Evaluation SISCOM Result in a patient with extratemporal epilepsy

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Presurgical Evaluation  Neuropsychological testing • Pre-operative baseline • Aid in localization • Predicting risk of cognitive decline with surgery

 Wada (intracarotid amobarbital) test • language

– lateralization • Memory

– prediction of postoperative decline S-Slide 8

Presurgical Evaluation  Intracranial EEG when needed • Grids and strips, most commonly subdural • Parenchymal “depth” electrodes, especially for recording from hipppocampus • Identification of ictal onset • Brain mapping

– cortical stimulation – SSEPs – Functional MRI S-Slide 9

Types of Surgical Procedures  Resective Surgery: single seizure focus in non-eloquent region.  Palliative Surgery: • For drop attacks: corpus callosotomy • For Rasmussen’s encephalitis or hemimegalencephaly: hemispherectomy

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Surgical Treatment of Epilepsy Figure 2

Curative

Palliative Pathologies

MTS TLE Lesional - Low Grade Glioma - Cav. Malformation

Non-MTS TLE Frontal Lobe epilepsy SMA/cingulate epilepsy Malformations of cortical development

Procedures Lesionectomy Lobectomy

Hemispherectomy Topectomy MST’s

Disconnection (Callosotomy)

Modified from McKhann G.M. and Howard M.A.: Epilepsy Surgery: Disease Treatment and Investigative Opportunity, in Diseases of the Nervous System: Clinical Neurobiology, Neurobiology, 2002.

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Surgical Treatment of Epilepsy  MRI frameless stereotactic localization of focal cortical dysplasia at the base of the central sulcus (center of cross hairs).

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Surgical Treatment of Epilepsy 

Functional hemispherectomy: extent of cortical resections in temporal and central cortex with disconnection of residual frontal and occipital cortex by transecting white matter fibers (not shown).

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Vagus Nerve Stimulation  The vagus nerve stimulator (courtesy of Cyberonics Inc.)

Reprinted with permission.

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Vagus Nerve Stimulation Percentage Change – All Seizures Results of two randomized, controlled trials in medically refractory partial seizures.

VNS Study Group, 1995 Handforth, et al., 1998

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Vagus Nerve Stimulation “Responder Rates” Responder rates from the randomized controlled trials

VNS Study Group, 1995 Handforth, et al., 1998

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Odds ratio for 50% responders

Metaanalysis of AEDs and VNS Efficacy 8 7 6 5 4 3 2 1 0

Marson et al (1997) S-Slide 17

Epilepsy and Head Injury  5% of all epilepsy may be attributed to head injury.  Most patients with early seizures after head injury do not develop epilepsy.  With loss of consciousness: 2% develop epilepsy  With hospitalization: 7-15% develop epilepsy

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Epilepsy and Head Injury  Risks to developing epilepsy: penetrating injury (up to 50%), early seizures, hemorrhage, low score in G.C.S., cortical lesion, volume lost, depressed fx, metal fragments, loss of consciousness.  60% of epilepsy occurs in within 1 yr., 80% in 2 yrs, 88% by 10 yrs.

Yablon, Arch Phys Med Rehab 1993. Willmore, Epilepsy: A Comprehensive Text 1997. S-Slide 19

Epilepsy and Head Injury  Mayo clinic study:  Severe injury (contusion, hematoma, focal deficit, 24 hr. of amnesia or LOC): 11.5% epilepsy (in 5 yr.)  Moderate injury (fracture, > 30 min LOC, amnesia): 1.6%  Milder injury: no increased risk.  Severe injury and early seizure: 36% Annegers., Neurology, 1980.

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Head Injury and Prophylactic AEDs  404 pts, severe head injury with cortical damage randomized in < 24 hr: DPH 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.

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