Volume 42, Issue 3 pp. 363-371

Relevance of Residual Histologic and Electrocorticographic Abnormalities for Surgical Outcome in Frontal Lobe Epilepsy

C. H. Ferrier

C. H. Ferrier

Institute of Epileptology, King's College Hospital, London, U.K.;

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G. Alarcon

G. Alarcon

Institute of Epileptology, King's College Hospital, London, U.K.;

Departamento de Fisiología, Facultad de Medicina, Universidad Complutense, Madrid, Spain; and

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J. Engelsman

J. Engelsman

Institute of Epileptology, King's College Hospital, London, U.K.;

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C. D. Binnie

C. D. Binnie

Institute of Epileptology, King's College Hospital, London, U.K.;

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M. Koutroumanidis

M. Koutroumanidis

Institute of Epileptology, King's College Hospital, London, U.K.;

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C. E. Polkey

C. E. Polkey

Institute of Epileptology, King's College Hospital, London, U.K.;

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I. Janota

I. Janota

Institute of Epileptology, King's College Hospital, London, U.K.;

Department of Neuropathology, Institute of Psychiatry, London, U.K.

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A. Dean

A. Dean

Institute of Epileptology, King's College Hospital, London, U.K.;

Department of Neuropathology, Institute of Psychiatry, London, U.K.

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First published: 01 May 2002
Citations: 53
Address correspondence and reprint requests to Dr. G. Alarcón at Department of Clinical Neurophysiology, King's College Hospital, Denmark Hill, London SE5 9RS, U.K.

Abstract

Summary: Purpose: To estimate the significance of residual electrocorticographic and neuropathologic abnormalities on seizure control after surgery for frontal lobe epilepsy with the purpose of determining their relevance in deciding the extent of the surgical procedure.

Methods: The presence of epileptiform discharges in intraoperative electrocorticograms (ECoGs) and the nature and extent of neuropathologic abnormalities were reviewed for 35 patients who underwent frontal lobe resections for the treatment of epilepsy at our institution. The relations between surgical outcome and presence of the following features were studied: (a) presence of abnormal tissue at the limits of the resection; (b) presence of sporadic spikes and seizure patterns in the preresection ECoG; (c) their abolition in the postresection ECoG; and (d) the topography of residual discharges with respect to the margins of the resection.

Results: On neuropathologic examination, 18 patients showed focal cortical dysplasia (CD), and 17 showed other abnormalities (non-CD). Ten CD patients and 11 non-CD patients experienced a favourable outcome. Seizure patterns were significantly more common in patients with focal cortical dysplasia than in those without, with a sensitivity of 94% and a specificity of 75%. Abolition of seizure patterns was associated with a favourable surgical outcome (p = 0.031). Abolition of sporadic spikes or their presence in the postresection ECoG did not influence outcome. There was no clear relation between outcome and location of residual sporadic discharges. Seizure patterns persisted in the postresection ECoG in three CD patients, were located at the margins of the resection in all three, and these patients had a poor outcome. Incomplete removal of abnormal tissue was not associated with a poorer outcome in either patient group or in the complete sample.

Conclusions: Seizure patterns were significantly more common in patients with cortical dysplasia, and their abolition on postresection ECoG recordings was associated with a favourable surgical outcome. Persistence of sporadic ECoG spikes and incomplete removal of histologic abnormalities did not affect outcome significantly.

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