Stereoelectroencephalography using computerized tomography– or magnetic resonance imaging–guided electrode implantation

[Stereoelectroencephalography by using O-Arm® and Vertek® passive articulated arm: Technical note and experience of an epilepsy referral centre]

OBJECTIVE

To report a novel, accurate, and safe technique for deep brain electrode implantation to register brain electrical activity or SEEG, using frameless stereotaxy, neuronavigation assisted, and intraoperative CT-guided O-Arm^® and the Vertek^® articulated passive arm.

MATERIAL AND METHODS

All patients implanted by this technique in Barcelona Hospital Clinic were included. A prospective evaluation was made of the accuracy of the technique, as well as complications, surgical time, length of stay, and short-term outcomes.

RESULTS

The study included 10 patients that underwent this procedure. The mean age was 38 years, and 60% were women. A mean of 6.9 (3-10) electrodes/patient, with a total of 69 electrodes, were implanted. The mean time for implantation was 34.7minutes per electrode. The mean distance between the planned target and the final target was 1.39 millimetres (0.95-1.7). There were no surgically derived complications. The epileptogenic zone was determined in 6 cases (60%). Surgical resection was performed in 5 cases (50%), with thermocoagulation in 3 (30%) cases, and in 2 cases (20%) there was no treatment. At a six-month follow-up of the 8 treated cases, 37.5% were ELAI I, 12.5% ELAI III, 25% ELAI IV, and 25% ELAI V.

CONCLUSIONS

The implantation of deep brain electrodes for SEEG by using intraoperative CT O-Arm^® and the Vertek^® articulated passive arm is a safe and effective technique with adequate accuracy.

Bilateral intracranial electrodes for lateralizing intractable epilepsy: efficacy, risk, and outcome

OBJECTIVE

Medically refractory epilepsy is amenable to neurosurgical intervention if the epileptogenic focus is accurately localized. If the scalp video-electroencephalography (EEG) and magnetic resonance imaging are nonlateralizing, yet a single focus is suspected, video-EEG monitoring with bilateral intracranial electrode placement is helpful to lateralize the ictal onset zone. We describe the indications, risks, and utility of such bilateral surveys at our institution.

METHODS

We retrospectively reviewed 26 patients with medically refractory seizures who were treated over a 5-year period and underwent bilateral placement of intracranial electrodes. Subdural strips were used in all cases, and additional stereotactic implantation of depth electrodes into mesial temporal lobes occurred in 50%. The mean patient age was 37.7 years, and 65.4% of patients were male.

RESULTS

The most common indication for bilateral invasive monitoring was bilateral ictal onsets on surface video-EEG (76.9%), followed by frequent interictal spikes contralateral to a single ictal focus (7.7%). Intracranial monitoring lasted an average of 8.2 days, with ictal events recorded in all cases. Ten patients (38.5%) subsequently underwent more extensive unilateral monitoring via implantation of subdural and depth electrodes through a craniotomy. A therapeutic procedure was performed in 17 patients (65.4%), whereas 1 patient underwent a palliative corpus callosotomy (3.8%). Nine patients underwent a resection without unilateral invasive mapping. Reasons for no therapeutic surgery (n = 8) included multifocal onsets, failing the Wada test, refusal of further treatment, and negative intraoperative electrocorticogram. There was 1 surgical complication, involving a retained electrode fragment that was removed in a separate minor procedure. Of the 26 patients, 15 (57.7%) are now seizure-free or have seizure disorders that have substantially improved (modified Engel classes I and II). Of the 17 patients who underwent a potentially curative surgery, 13 (76.5%) were Engel classes I and II.

CONCLUSION

Bilateral placement of subdural strip and depth electrodes for epilepsy monitoring in patients with nonlateralizing scalp EEG and/or discordant imaging studies but clinical suspicion for focal seizure origin is both safe and effective. Given the safety and efficacy of this procedure, epileptologists should have a low threshold to consider bilateral implants for suitable patients.