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1 Epilepsy Surgery Seung Bong Hong, M.D. Eun Yeon Joo, M.D. Department of Neurology Sungkyunkwan University School of Medicine, Samsung Medical Center E mail : sbhong@smc.samsung.co.kr jey1220@freechal.com Abstract Epilepsy is a chronic neurological disorder manifesting recurrent unprovoked epileptic seizures. About 20~30% of epilepsy patients are resistant to antiepileptic medications. These patients suffer from high risk of physical injury, unemployment, marital problem, and psychological stress. Epilepsy surgery is the firstly recommended treatment modality for the patients with medically intractable epilepsy. Presurgical evaluation is the most important process for performing epilepsy surgery. The ultimate goal of the presurgical evaluation in patients with medically refractory partial seizures is the localization of the epileptogenic zone and the resection of which is also both necessary and sufficient to render the patient seizure free. The localization of the epileptogenic zone derives from a hierarchical synthesis of localizing data independently obtained from clinical, electrographic, neuroimaging, and neuropsychological examination. In addition, closely related to the goal of localizing the epileptogenic zone is the significant need for anticipating the risks of functional deficits that could derive from the surgical resection. Mesial temporal lobe epilepsy (TLE) is the best candidate for epilepsy surgery. Anterior temporal lobectomy with amygdalohippocampectomy is a surgical treatment method for mesial TLE and its seizure free rate (SFR) is 60 90%, whereas one year SFR of antiepileptic drug treatment for mesial TLE is 10 20%. Cortisectomy is a surgical method for extratemporal epilepsy and its SFR is about 40 70%. Corpus callosotomy is a partial or complete division of corpus callosum for preventing seizure propagations between right and left hemispheres and is effective for controlling atonic seizures. The variation of postsurgical seizure outcomes is related to the qualities of epilepsy surgery program, presurgical evaluation and surgical techniques. For the good surgical outcome, the epilepsy surgery program should include neurologist, neurosurgeon, neuropsychologist, neuro radiologist and neuro nuclear medicine specialist for a comprehensive team approach. Keywords : Intractable epilepsy; Presurgical evaluation; Epilepsy surgery; Anterior temporal Lobectomy with amygdalohippocampectomy; Cortisectomy; Corpus callosotomy 253

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3 One year seizure free rate with medical treatment in different etiology Etiology of epilepsy One year seizure free rate Idiopathic generalized epilepsy 82% Cryptogenic partial epilepsy 45% Symptomatic partial epilepsy 35% Extratemporal partial epilepsy Temporal lobe epilepsy 36% 20% Hippocampal sclerosis 11% Dual pathology (HS+) 3% Dysgenesis Dual pathology (HS+): hippocampal sclerosis and other pathology 24% 255

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6 Contents of presurgical evaluation Performed invariably Performed variably Performed in selected centers History and examination Video EEG (intracranial) SISCOM Routine EEG Electrocorticography MRS Brain MRI FDG PET MEG Video EEG(extracranial) Interictal and ictal SPECT MRI special study Neuropsychology Wada test fmri Performed invariably: almost always obtained prior to epilepsy surgery. Performed variably: available at most epilepsy centers, used in selected candidates. Performed in selected centers: not widely available. MRI: magnetic resonance imaging, PET: positron emission tomography, SPECT: single photon emission computed tomography. SISCOM: subtraction ictal SPECT co registered to MRI, MRS: magnetic resonance spectroscopy, MEG: magnetoencephalography, MRI special study: volumetry, 3 D rendering, gyroscan, etc. 258

7 R Left hippocampal sclerosis. T2 weighted (left) and fluid attenuated inversion recovery (FLAIR, right) MR images show decreased volume and increased signal in left hippocampus (arrow) in a patient with left mesial temporal lobe epilepsy. MRI images were obtained from Samsung Medical Center. L 259

Ideal MR sequence characteristics High signal to noise ratio High spatial resolution Thin slices or 3D data sets High contrast between normal tissues High contrast between pathological and normal

8 Ideal MR sequence characteristics High signal to noise ratio High spatial resolution Thin slices or 3D data sets High contrast between normal tissues High contrast between pathological and normal tissue No artifacts (e.g., motion, partial volume) Short time of acquisition Quiet pulse sequences The ability to reformat the data in any plane MRI PET co registration. A 7 year old girl has suffered from frequent supplementary motor area seizures occurring several times per a night. Her brain MRI (A) showed no abnormality whereas brain FDG PET (B) revealed a definite hypometabolism on left medical frontal region (arrow). Fused image (C) of MRI and FDG PET could localize the hypometabolic zone on the patient s MRI. MRI and FDG PET images were obtained from Samsung Medical Center. 260

A C Transmantle dysplasia right frontal axial T2 FSE (D) and axial magnetization prepared rapid gradient echo (B), a thin section volumetric T1 weighted sequence (right) obtained with a 3T PA MRI

9 A C Transmantle dysplasia right frontal axial T2 FSE (D) and axial magnetization prepared rapid gradient echo (B), a thin section volumetric T1 weighted sequence (right) obtained with a 3T PA MRI showing a subtle right frontal cone shaped region of increased T2 signal that begins at the ventricular margin and extends to the depth of a sulcus (see arrowheads in D). The lesion corresponds to a more subtle region of decreased T1 signal (arrowheads, B). On close scrutiny of the overlying cortex, increased T2 signal (arrows, D) and increased T1 signal (arrows, B) with blurring of the gray white junction is identified. Previous high resolution 1.5T MRI obtained with a regular head coil did not show the lesion (A, T1 weighted image, C, T2 weighted image). Due to different imaging protocols, the two images are angled slightly differently and have different slice thickness (1.5T images courtesy Dr. P. Due T TM nnessen, Dept. of Radiology, Rikshospitalet Olso, Norway). This figure was quoted on the permission of Dr. P. Ellen Grant. B D 261

24 hour video EEG monitoring unit. In the video EEG monitoring room, patients EEG and behavior are being recorded and monitored by Vanguard EEG system and trained EEG technicians.

This picture was obtained from Epilepsy Monitoring Unit in Samsung Medical Center.

10 24 hour video EEG monitoring unit. In the video EEG monitoring room, patients EEG and behavior are being recorded and monitored by Vanguard EEG system and trained EEG technicians. If a patient starts having a seizure, a technician should run into a monitoring room and perform a seizure interview, and may inject a radiotracer for ictal SPECT study. This picture was obtained from Epilepsy Monitoring Unit in Samsung Medical Center. Ictal scalp EEG recorded during clinical seizures shows rhythmic discharges (arrow) on left temporal lobe with many muscle artifacts (arrow head). The EEG montage in left column indicates left hemisphere by odd numbers whereas right hemisphere by even numbers. This patient has a left hippocampal sclerosis on her brain MRI. She has been seizure free after her anterior temporal lobe and amygdala/hippocampus were resected. The EEG data were obtained from Samsung Medical Center. 262

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12 A 69 B Ictal SPECT and SISCOM. Ictal SPECT (A) shows increased cerebral blood flow on right anterior frontal region (arrow). SISCOM (B) shows very well localized ictal hyperperfusion (arrow) on right hippocampus and insular cortex in a patient with right mesial temporal lobe epilepsy. Ictal SPECT and SISCOM images were obtained from Samsung Medical Center. 264

Subdural electrodes are placed on cortical surface whereas a depth electrode is placed on deeper brain structures such as

stereotactic frames or with a frameless stereotactic technique. A Subdural grid electrode insertion.

13 A B C Intracranial electrodes. (A) is a 1 8 subdural strip electrode, (B) is a 4 8 subdural grid electrode and (C) is a 1 8 depth electrode. Subdural electrodes are placed on cortical surface whereas a depth electrode is placed on deeper brain structures such as bilateral hippocampi and interhemispheric medial frontal regions by piercing cerebral cortex and white matter with either stereotactic frames or with a frameless stereotactic technique. A Subdural grid electrode insertion. (A) shows subdural grid electrodes (4 8) placed on right frontoparietal cortex. (B) demonstrates the location of subdural grid (4 8) and strip (1 8) electrodes on the patient s 3D brain by a CT MRI co registration technique. The images were obtained from Samsung Medical Center. B 265

Intracranial cortical EEG. This patient is a 7 year old girl who had suffered from frequent bilateral tonic seizures with preserved consciousness.

14 Intracranial cortical EEG. This patient is a 7 year old girl who had suffered from frequent bilateral tonic seizures with preserved consciousness. Well localized EEG seizure discharges (low amplitude rhythmic fast activities) were recorded during clinical seizures on left surperior frontoparietal regions of subdural grid electrodes. Intracranial EEG recording and a functional map by electrical cortical stimulation are necessary for determining a resection margin of neocortical epilepsy. The intracranial EEG data were obtained from Samsung Medical Center. 266

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16 ,, MRI, EEG review Further drug therapy Uni mtle mtle Partial epilepsy Bi mtle Neocortical epilepsy MRI lesion? Generalized epilepsy Atonic seizure Tonic seizure Non epileptic seizure Syncope Psychogenic seizure PKC Cataplexy TIA Hypoglycemia HS on MRI? Yes No or Bi FDG PET no FDG PET yes Lesion vs EEG Callosotomy? Specific therapy Unitemporal hypom Bitemporal hypom & & Surgery with ECoG? Bi depth or Strip electr. Uni mtle or Bi mtle but Ipsi contra More drug intractable Bi mtle & Ipsi contra Well localized, no functional area Cortisectomy Localized, but overlapped with functional area Functional hemispherectomy Cortisectomy with MST More drug therapy Other methods ATL & AH mtle: mesial temporal lobe epilepsy, Neo.: neocortical, Gen.: generalized, HS: hippocampal sclerosis, Uni.: unilateral, Bi: bilateral, FDG PET: 18F fluorodeoxy glucose positron emission tomography, hypom: hypometabolism, electr: electrode, ipsi: ipsilateral to epileptic focus, contra: contralateral to epileptic focus, MST: multiple subpial transection, ECoG: intraoperative electrocorticography, PKC: paroxysmal kinesogenic choreoathetosis, Ipsi contra: Ipsilateral hippocampal seizure origin is much more frequent than contralateral origin. Ipsi contra: Ipsilateral hippocampal seizure frequency is similar to contralateral seizure frequency. TIA: transient ischemic attack, ATL & AH: anterior temporal lobectomy & amygdalohippocampectomy. Decision making cascade for intractable epilepsy patients 268

17 1. Penfield W, Flanigin H. Surgical therapy of temporal lobe seizures. Arch Neurol Psychiatry 1950; 64: Bailey P, Gobbs FA. The surgical treatment of psychomotor epilepsy. J Am Med Assoc 1951; 145: Engel J Jr, Wiebe S, French J, Sperling M, Williamson P, Enos B, et al. Practice parameter: temporal lobe and localized neocortical resections for epilepsy. Epilepsia 2003; 44:

18 4. Semah F, Picot MC, Adam C, Broglin D, Arzimanoglou A, Baulac M, et al. Is the underlying cause of epilepsy a major prognostic factor for recurrence? Neurology 1998; 51: Wiebe S, Blume WT, Girvin JP, Eliasziw M. A randomized, controlled trial of surgery for temporal lobe epilepsy. N Engl J Med 2001; 345: Kuzniecky R, Jackson G. Neuroimaging in epilepsy: magnetic resonance in epilepsy. New York: Raven Press, 1995: Jack CJ, Sharbrough FW, Twomey CK, et al. Temporal lobe seizures: lateralization with MR volume measurements of the hippocampal formations. Radiology 1993; Jack C, Rydberg C, Kreacker K, et al. Mesial temporal sclerosis: diagnosis with FLAIR versus spin echo MR imaging. Radiology 1996; 199: Jackson GD, Berkovic SF, Duncan JS, et al. Optimizing the diagnosis of hippocampal sclerosis using magnetic resonance imaging. AJNR Am J Neuroradiol 1993; 14: Kuzniecky R, Cascino GD, Palmini A, et al. Structural imaging. In: Engel J Jr, ed. Surgical treatment of the epilepsies, 2nd ed. New York: Raven Press, 1993: Gadian DG. Nuclear magnetic resonance and its applications to living systems. New York: Oxford University Press, Cascino GD, Jack CR, Jr, Hirschorn KA, Sharbrough FW. Identification of the epileptic focus: magnetic resonance imaging. Epilepsy Res Suppl 1992; 5: Knake S, Triantafyllou C, Wald LL, Wiggins G, Kirk GP, Grant PE, et al. 3T phased array MRI improves the presurgical evaluation in focal epilepsies: a prospective study. Neurology 2005; 65: Lagerlund TD, Cascino GD, Cicora KM, Sharbrough FW. Long term electroencephalographic monitoring for diagnosis and management of seizures. Mayo Clin Proc 1996; 71: ,,,,,. SPECT PET. 1998; 16: Spencer SS, Theodore WH, Berkovic SF. Clnical applications: MRI, SPECT, and PET. Magn Reson Imaging 1995; 13: Lee HW, Hong SB, Tae WS. Opposite ictal perfusion patterns of subtracted SPECT. Hyperperfusion and hypoperfusion. Brain 2000; 123: O'Brien TJ, So EL, Mullan BP, et al. Subtraction peri ictal SPECT is predictive of extratemporal epilepsy surgery outcome. Neurology 2000; 55: Choi JY, Kim SJ, Hong SB, et al. Extratemporal hypometabolism on FDG PET in temporal lobe epilepsy as a predictor of seizure outcome after temporal lobectomy. Eur J Nucl Med Mol Imaging 2003; 30: Hong SB, Kim KW, Seo DW, Kim SE, Na DG, Byun HS. Contralateral EEG slowing and amobarbital distribution in Wada test: an intracarotid SPECT study. Epilepsia 2000; 41: Hong SB, Han HJ, Roh SY, Seo DW, Kim SE, Kim MH. Hypometabolism and interictal spikes during positron emission tomography scanning in temporal lobe epilepsy. Eur Neurol 2002; 48: Behrens E, Zentner J, van Roost D, Hufnagel A, Elger CE, Schramm J. Subdural and depth electrodes in the presurgical evaluation of epilepsy. Acta Neurochir (Wien) 1994; 128: Wass CT, Grady RE, Fessler AJ, et al. The effects of remifentanil on epileptiform discharges during intraoperative electrocorticography in patients undergoing epilepsy surgery. 270

19 Epilepsia 2001; 42: Fiol ME, Gates JR, Torres F, Maxwell RE. The prognostic value of residual spikes in the postexcision electrocorticogram after temporal lobectomy. Neurology 1991; 41: Engel J Jr. Wiebe S, French J, Sperling M, Williamson P, Gumnit R, et al. Practice parameter: temporal lobe and localized neocortical resections for epilepsy: report of the Quality Standards Subcommittee of the American Academy of Neurology, in association with the American Epilepsy Society and the American Association of Neurological Surgeons. Neurolgy 2003; 60: Daniel RT, Joseph TP, Gnanamuthu C, Chandy MJ. Hemispherotomy for paediatric hemispheric epilepsy. Stereotact Funct Neurosurg 2001; 77: Pulsifer MB, Brandt J, Salorio CF, Vining EP, Carson BS, Freeman JM. The cognitive outcome of hemispherectomy in 71 children. Epilepsia 2004; 45: Spencer SS, Schramm J, Wyler A, O Connor M, Orbach D, Krauss G, et al. Multiple subpial transection for intractable partial epilepsy: an international meta analysis. Epilepsia 2002; 43: Orbach D, Romanelli P, Devinsky O, Doyle W. Late seizure recurrence after multiple subpial transections. Epilepsia 2001; 42: Tellez Zenteno JF, Dhar R, Wiebe S. Long term seizure outcomes following epilepsy surgery: a systematic review and meta analysis. Brain 2005; 128: Sass KJ, Spencer DD, Spencer SS, Novelly RA, Williamson PD, Mattson RH. Corpus callosotomy for epilepsy. II. Neurologic and neuropsychological outcome. Neurology 1988; 38: Spencer SS, Spencer DD, Williamson PD, Sass K, Novelly RA, Mattson RH. Corpus callosotomy for epilepsy. I. Seizure effects. Neurology 1988; 38: Peer Reviewer Commentary 271

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10 ÀÇÇÐ°�ÁÂc10«½ÂºÀ£07à°£347~357 Epilepsy Surgery Seung Chyul Hong, M.D. Jung Il Lee, M.D. Dae Won Seo, M.D. Seung Bong Hong, M.D. Department of Neurosurgery Neurology* Sungkyunkwan University School of Medicine, Samsung Medical Center