E/Ji/epS;U, zyxwvutsrqponmlkjihg 39(3):259-266, zyxwvutsrqpo 1998 zyxwvutsrqponm Lippincotr-Ravcn Publishers, Philadelphia zyxwvutsrqpon 0 International Lcague Ageinst Epilepsy Intracranial EEG Seizure-Offset Termination Patterns: Relation to Outcome of Epilepsy Surgery in Temporal Lobe Epilepsy Geert J. F. Brekelmans, Demetrios N. Velis, Cees W. M. van Veelen, “Peter C. van Rijen, Fernando H. Lopes da Silva, and Walter van Emde Boas zyxw Department of Clinical Neurophysiology, Instituut voor Epilepsiebestrijding “Meer en Bosch zyxw ”/’ ‘De Cruquiushoeve, ” Heemstede; and *Department of Neurosurgery, University Hospital Utrecht, The Netherlands Summary: Purpose: Studies using stereo-EEG (SEEG) and electrocorticography (ECoG) should not only identify a pa- tient’s epileptogenic zone, but also should provide prognostic information for surgical outcome. In this respect, seizure-offset patterns have so far been the subject of only one study, in which they were shown to be associated with poor outcome when recorded over cortical areas outside the temporal lobe of sei- zure onset. To clarify whether seizure-offset patterns are reli- able in predicting seizure outcome, we studied SEEG/ECoG in a similar group of patients with temporal lobe epilepsy (TLE). Methods: SEEGECoG records of 44 patients with refractory TLE were analyzed. The areas of seizure termination were classified as ipsilateral or contralateral (mesial and/or lateral) temporal, (temporal and) frontal, and diffusehilateral. Patients were classified with respect to seizure outcome as either sei- zure-free (UCLA class la) or not seizure free (UCLA class 24); both groups were correlated with specific seizure-offset categories using Fisher’s exact probability test and analysis of variance (ANOVA). Results: Of the 44 patients, the majority (n = 36) had at least part of their seizure offsets in the ipsilateral temporal lobe, whereas 8 patients manifested no seizure offsets in this lobe. Only 9 patients (20%) showed exclusive offsets in the ipsilat- eral temporal lobe. No statistically significant difference was evident between patients with all seizure offsets in the ipsilat- eral temporal lobe and those with offsets elsewhere. Similarly, no statistically significant difference was evident between pa- tients with a diffuse seizure offset and those with seizure offsets of a different category. Conclusions: Seizure-offset patterns in SEEGECoG are un- reliable in predicting seizure outcome after resective activity surgery for TLE. Key Words: Epilepsy surgery-Intracranial EEG-Prognosis-Outcome. Precise localization of the zone of ictal onset is a pre- requisite for successful epilepsy surgery in patients with medically refractory partial seizures. If noninvasive functional and structural investigations provide equivo- cal or nonconvergent results, EEG/video seizure moni- toring, including subchronic electrocorticography (ECoG) and stereo-EEG (SEEG) may be indicated (1-3). Data collected during these studies should help identify the epileptogenic zone that must be removed as well as functionally important cortical areas that must be spared (4). Ideally, these tests should also provide prognostic information regarding the likelihood of successful out- come of surgery to optimize presurgical counseling of the patient. Various ECoG/SEEG parameters, notably the site of seizure onset, but also morphology of seizure onset and patterns of seizure propagation, have been re- ported to be valid in this regard (5-7). Seizure-offset patterns have, so far, been the subject of only one study, in which seizure offset in cortical areas outside the tem- poral lobe of seizure onset was associated with poor outcome after surgery (8). In the present study we wished to clarify whether sei- zure-offset patterns are reliable in predicting seizure out- come. We studied a similar group of patients with tem- poral lobe epilepsy (TLE) and investigated their seizure- offset patterns with intracranial electrodes (9-14). In addition, we investigated whether such seizure-offset patterns outside the lobe of resected seizure-onset areas represent potential secondary epileptogenic zones pre- dictive of seizure recurrence in patients in whom antiep- ileptic drugs (AEDs) have been discontinued after suc- cessful temporal lobe surgery. Accepted September 18, 1997. Address correspondence and reprint requests to Dr. G. J. F. PATIENTS AND METHODS Brekelmans at Instituut voor Epilepsiebestrijding “Meer en Bosch”/ “De Cruquiushoeve,” Achterweg 5, 2103 SW Heemstede, The Neth- erlands. ECoG/SEEG records of 44 patients with refractory (mesial and/or temporal neocortical) TLE (22 males and 259