Surgical technique.

In SEEG, as for any surgical procedure, the benefit/risk ratio is a key-point. This implies rigorous clinical practice in terms of indication, information delivered to the patient, and surgical technique. Numerous technical options may be used to achieve this goal. All are valuable, as long as they are executed with rigor and consistency. Intracranial bleeding represents the main risk of the procedure (1-4% of cases). The procedure also carries a risk of infection (0.8%), death (total of 6 reported cases in all the literature, <0.002%), and of minor and transient side effects. SEEG is performed under general anesthesia. MRI is the gold standard morphological imaging, used for targeting and for trajectory calculations. It is strictly necessary to use some form of vascular imaging to minimize the peroperative bleeding risk. SEEG can be performed on a frame-based, or frameless, basis, using stereotactic instrumentation, or a neurosurgical robot. Literature does not provide any data in favour of one of these techniques compared to the other. The minimal acceptable bone thickness is considered to be 2mm. Postoperatively, as soon as any non-preexisting neurological deficit is noticed, neuroimaging must immediately be performed. It is recommended to perform a postoperative imaging during the 24hours after implantation. The numerous current possibilities, in terms of imaging and technology, give rise to many possible stereotactic strategies for performing SEEG implantation. None of these strategies can be considered as superior to the other. The guarantee of the best possible result is provided by the care with which these procedures are done.