We read with great interest the article by Hader et al. (2013), highlighting the safety of the most common surgical procedures performed for treating partial drug-resistant epilepsies. The authors report the results of a systematic review aimed at analyzing the morbidity in the context of epilepsy surgery, and conclude hoping “that these findings will increase the likelihood of appropriate referrals to specialized epilepsy centers for surgical evaluation.” In fact, the complication rate is generally low and the majority of adverse events are minor or temporary. This point can be strengthened not only considering the morbidity rate of epilepsy surgery itself, but also remembering that patients with drug-resistant epilepsy are at higher risk of sudden death and injuries, as well as psychosocial dysfunction and impaired quality of life (Kwan et al., 2011).
The literature search covers the period from 1990 to June 2008, looking for all studies in English that report seizure outcomes and complications from focal resective surgery and invasive electroencephalography (EEG) monitoring. Therefore, the authors report the complications that occurred during the implantation of depth electrodes and subdural grids and strips, positioned by means of burr hole, twist drill, or craniotomy.
Surprisingly, no studies reporting on stereo-EEG (SEEG) were included in the Systematic Review Results listed in Hader et al.'s (2013) Supporting Information. SEEG is a methodology developed by Talairach and Bancaud at Hôpital Saint Anne, Paris, France (Bancaud et al., 1965). Unlike depth electrodes (DE), the main goal of which is to lateralize the origin of the seizures, SEEG methodology aims to define the epileptogenic zone (EZ) by way of implanting a larger number of intracerebral electrodes according to a presurgical strategy based on the anatomoelectroclinical correlations (Munari et al., 1994). Some reports have clearly stated that, despite the number of electrodes, this result can be obtained with a very low complication rate (Cossu et al., 2005a,b; McGonigal et al., 2007). More recently, our group reported the results from a consecutive series of 500 SEEG procedures, with the last 81 (1,050 electrodes) performed according to an updated work flow (Cardinale et al., 2013). Only one status epilepticus and four minor complications occurred with the new method, which is based on three-dimensional image-guided robotic stereotactic implantation of the electrodes. Therefore, the major and minor complication rates per electrode were 0.1% and 0.4%, respectively. From an effectiveness perspective, 56% of the patients who underwent focal resections are free of disabling seizures with a minimum follow-up of 12 months. Gonzalez-Martinez and Bingaman reported in 2012 that “SEEG may be considered a rediscovered methodology that differs in principle from any other current method for extra-operative long-term monitoring used in the diagnosis and treatment of refractory focal epilepsy.”
In conclusion, we would like to highlight the historical rule and the future perspectives of SEEG, a methodology aimed at defining the EZ that is spreading beyond the European boundaries because it enables safe and effective recordings from every cerebral structure.