Monopolar stereoelectroencephalography-guided radiofrequency thermocoagulation

Area of Science:

• Neurosurgery
• Epileptology
• Interventional Neuroradiology

Background:

• Stereoelectroencephalography (SEEG) is a crucial tool for localizing the epileptogenic zone (EZ) in drug-resistant focal epilepsy.
• Radiofrequency thermocoagulation (RFTC) allows for lesioning of the EZ guided by SEEG.
• Traditional SEEG-guided RFTC typically employs bipolar lesional techniques between adjacent electrode contacts.

Purpose of the Study:

• To evaluate the safety, efficacy, and benefits of monopolar RFTC performed at the conclusion of SEEG.
• To assess seizure control outcomes following monopolar RFTC.
• To compare monopolar RFTC outcomes with subsequent epilepsy surgery outcomes.

Main Methods:

• A retrospective analysis of 31 consecutive patients with drug-resistant focal epilepsy who underwent monopolar RFTC post-SEEG between January 2013 and December 2019.
• Assessment of seizure control at 2 months and last follow-up (mean 18 months).
• Comparison of seizure outcomes between patients who underwent subsequent resective surgery and those treated solely with RFTC.

Main Results:

• A total of 446 monopolar RFTCs were performed across various cortical areas, including the insula in 11 patients.
• Lesion volumes ranged from 44-56 mm³ (mean 50 mm³).
• At 2 months, 41.9% of patients achieved seizure freedom and 35.5% had ≥50% seizure reduction. At last follow-up, 64.5% had ≥50% seizure reduction.
• Monopolar RFTC demonstrated a high positive predictive value (93.8%) for subsequent surgical outcomes.
• A single complication (3.2%) of intraventricular hematoma resolved spontaneously.

Conclusions:

• Monopolar SEEG-guided RFTC provides enhanced flexibility in contact selection and allows for larger thermolesion volumes compared to bipolar techniques.
• This method is particularly advantageous for targeting the insular EZ, potentially overcoming vascular limitations.
• Monopolar RFTC is a safe and effective adjunctive therapy for drug-resistant focal epilepsy, offering significant seizure reduction in a majority of patients.