title: Stereoelectroencephalography-guided radiofrequency thermocoagulation in the epileptogenic zone: a retrospective study on 89 cases.
abstract: OBJECTIVE
  Radiofrequency thermocoagulation (RF-TC) of presumed epileptogenic lesions and/or structures has gained new popularity as a treatment option for drug-resistant focal epilepsy, mainly in patients with mesial temporal lobe epilepsy. The role of this minimally invasive procedure in more complex cases of drug-resistant epilepsy, which may require intracranial electroencephalographic evaluation, has not been fully assessed. This retrospective study reports on a case series of patients with particularly complex focal epilepsy who underwent stereoelectroencephalography (SEEG) evaluation with stereotactically implanted multicontact intracerebral electrodes for the detailed identification of the epileptogenic zone (EZ) and who received RF-TC in their supposed EZ (according to SEEG findings).
  
  
  METHODS
  Eighty-nine patients (49 male and 40 female; age range 2-49 years) who underwent SEEG evaluation and subsequent RF-TC of the presumed EZ at the authors' institution between January 2008 and December 2013 were selected. Brain MRI revealed structural abnormalities in 43 cases and no lesions in 46 cases. After SEEG, 67 patients were judged suitable for resective surgery (Group 1), whereas surgery was excluded for 22 patients (Group 2). Thermocoagulation was performed in each of these patients by using the previously implanted multicontact recording electrodes and delivering RF-generated currents to adjacent electrode contacts.
  
  
  RESULTS
  The mean number of TC sites per patient was 10.6 ± 7.2 (range 1-33). Sustained seizure freedom occurred after TC in 16 patients (18.0%) (13 in Group 1 and 3 in Group 2). A sustained worthwhile improvement was reported by 9 additional patients (10.1%) (3 in Group 1 and 6 in Group 2). As a whole, 25 patients (28.1%) exhibited a persistent significant improvement in their seizures. More favorable results were observed in patients with nodular heterotopy (p = 0.0001389), those with a lesion found on MRI (not significant), and those with hippocampal sclerosis (not significant). Other variables significantly correlated to seizure freedom were the patient's age (p = 0.02885) and number of intralesional TC sites (p = 0.0271). The patients in Group 1 who did not benefit at all (21 patients) or who experienced only a transient benefit (30 patients) from TC underwent microsurgical resection of their EZ. Thermocoagulation was followed by severe permanent neurological deficits in 2 patients (an unexpected complex neuropsychological syndrome in one patient and an expected and anticipated permanent motor deficit in the other).
  
  
  CONCLUSIONS
  This study provides evidence that SEEG-guided TC in the EZ may be a treatment option for particularly complex drug-resistant focal epilepsy that requires invasive evaluation. A small subset of patients who achieve seizure freedom or worthwhile improvement may avoid open surgery or take advantage of an otherwise unexpected treatment if resection is not an option. Patients with epileptogenic nodular heterotopy are probably ideal candidates for this treatment.
authors.affiliation: Epilepsy Surgery Center and.
authors.forename: Massimo
authors.initials: M
authors.lastname: Cossu
authors.affiliation: Section of Neurosurgery, Department of Neurosciences and of Sense Organs, University of Milan; and.
authors.forename: Dalila
authors.initials: D
authors.lastname: Fuschillo
authors.affiliation: Epilepsy Surgery Center and.|Department of Neuroscience, University of Parma, Italy.
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Casaceli
authors.affiliation: Epilepsy Surgery Center and.|Department of Neuroscience, University of Parma, Italy.
authors.forename: Veronica
authors.initials: V
authors.lastname: Pelliccia
authors.affiliation: Epilepsy Surgery Center and.
authors.forename: Laura
authors.initials: L
authors.lastname: Castana
authors.affiliation: Epilepsy Surgery Center and.
authors.forename: Roberto
authors.initials: R
authors.lastname: Mai
authors.affiliation: Epilepsy Surgery Center and.
authors.forename: Stefano
authors.initials: S
authors.lastname: Francione
authors.affiliation: Epilepsy Surgery Center and.
authors.forename: Ivana
authors.initials: I
authors.lastname: Sartori
authors.affiliation: Epilepsy Surgery Center and.
authors.forename: Francesca
authors.initials: F
authors.lastname: Gozzo
authors.affiliation: Epilepsy Surgery Center and.|Center of Sleep Medicine, Department of Neuroscience, Niguarda Hospital, Milan;
authors.forename: Lino
authors.initials: L
authors.lastname: Nobili
authors.affiliation: Epilepsy Surgery Center and.
authors.forename: Laura
authors.initials: L
authors.lastname: Tassi
authors.affiliation: Epilepsy Surgery Center and.
authors.forename: Francesco
authors.initials: F
authors.lastname: Cardinale
authors.affiliation: Epilepsy Surgery Center and.
authors.forename: Giorgio
authors.initials: G
authors.lastname: Lo Russo
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D002675:Child, Preschool; D004564:Electrocoagulation; D004567:Electrodes, Implanted; D004569:Electroencephalography; D004828:Epilepsies, Partial / Q000175:diagnosis* / Q000503:physiopathology / Q000601:surgery*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D013238:Stereotaxic Techniques; D025321:Surgery, Computer-Assisted; D016896:Treatment Outcome; D055815:Young Adult
keywords: EEG = electroencephalography; EZ = epileptogenic zone; FCD = focal cortical dysplasia; MTLE = mesial temporal lobe epilepsy; RF-TC = radiofrequency thermocoagulation; SEEG = stereoelectroencephalography; epilepsy surgery; epileptogenic zone; radiofrequency thermocoagulation; seizure outcome; stereo-EEG