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  • Author or Editor: Roberto Mai x
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Massimo Cossu, Francesco Cardinale, Nadia Colombo, Roberto Mai, Lino Nobili, Ivana Sartori and Giorgio Lo Russo

Object

The authors report on indications for, techniques of, and results of stereoelectroencephalography (stereo-EEG) monitoring in the presurgical evaluation of childhood drug-resistant focal epilepsy.

Methods

Thirty-five children (24 boys and 11 girls; mean age 8.8 ± 3.9 years; mean age at seizure onset 2.1 ± 2.2 years) underwent 37 tailored stereotactic placements of intracerebral, multilead electrodes for intensive monitoring of seizures (stereo-EEG). Two children underwent exploration twice. Investigations prior to stereo-EEG monitoring, including magnetic resonance imaging and video-EEG of the scalp, revealed variable patterns of localizing incoherence among clinical, electrophysiological, and anatomical findings in all cases. A total of 426 electrodes were implanted (mean 11.5 ± 2.6 per procedure) according to individualized arrangements.

The stereo-EEG monitoring enabled recording of 826 seizures (mean 22 ± 45 per procedure) and mapping of critically functional areas. One untoward event consisted of intracranial breakage of an electrode. Resections of the epileptogenic zone were performed according to results of stereo-EEG recordings. They consisted of cortical removal in seven cases, removal of the lesion and epileptogenic cortex in 26 cases, and lesion removal in two cases. Transient postoperative neurological deficits were observed in 13 patients, and permanent anticipated visual field defects occurred in seven patients. According to the Engel postoperative classification of seizure outcome, 60% of cases were in Class I, 74% had significant improvement (Classes I–III), and 26% were unchanged (mean follow up 31.9 ± 20.6 months).

Conclusions

Stereoelectroencephalography monitoring is a helpful and well-tolerated technique for the definition of the epileptogenic zone in complex cases of childhood drug-resistant epilepsy. It provides essential information for safe resections that should result in excellent outcomes in a considerable number of patients.

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Massimo Cossu, Dalila Fuschillo, Giuseppe Casaceli, Veronica Pelliccia, Laura Castana, Roberto Mai, Stefano Francione, Ivana Sartori, Francesca Gozzo, Lino Nobili, Laura Tassi, Francesco Cardinale and Giorgio Lo Russo

OBJECT

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.