S tereoelectroencephalography (SEEG) is the recording of the brain's electrical activity through depth electrodes implanted in the parenchyma of the brain. SEEG is indicated in select patients with pharmacoresistant focal epilepsy to delineate the irritative and seizure onset zones and their relationship to eloquent cortical areas and white matter tracts.5 SEEG can be implemented with frame-based and frameless methods of implantation. 2,8 SEEG planning is a necessary prerequisite to implementation. A number of factors are considered when planning an electrode arrangement for SEEG (Table 1). Individual electrodes should enter at the crown of the gyrus to avoid sulcal boundaries and should avoid vascular structures. Furthermore, the electrode should enter at a reasonable angle perpendicular to the skull to enable the trajectory to be drilled with precision.abbreviatioNs CAP = computer-assisted planning software; IQR = interquartile range; SEEG = stereoelectroencephalography. obJective The objective of this study was to evaluate the clinical utility of multitrajectory computer-assisted planning software (CAP) to plan stereoelectroencephalography (SEEG) electrode arrangements. methods A cohort of 18 patients underwent SEEG for evaluation of epilepsy at a single center between August 2013 and August 2014. Planning of electrodes was performed manually and stored using EpiNav software. CAP was developed as a planning tool in EpiNav. The user preselects a set of cerebral targets and optimized trajectory constraints, and then runs an automated search of potential scalp entry points and associated trajectories. Each trajectory is associated with metrics for a safety profile, derived from the minimal distance to vascular structures, and an efficacy profile, derived from the proportion of depth electrodes that are within or adjacent to gray matter. CAP was applied to the cerebral targets used in the cohort of 18 previous manually planned implantations to generate new multitrajectory implantation plans. A comparison was then undertaken for trajectory safety and efficacy. results CAP was applied to 166 electrode targets in 18 patients. There were significant improvements in both the safety profile and efficacy profile of trajectories generated by CAP compared with manual planning (p < 0.05). Three independent neurosurgeons assessed the feasibility of the trajectories generated by CAP, with 131 (78.9%) of 166 trajectories deemed suitable for implementation in clinical practice. CAP was performed in real time, with a median duration of 8 minutes for each patient, although this does not include the time taken for data preparation. coNclusioNs CAP is a promising tool to plan SEEG implantations. CAP provides feasible depth electrode arrangements, with quantitatively greater safety and efficacy profiles, and with a substantial reduction in duration of planning within the 3D multimodality framework.