Abstracts

Rationale: We implemented a workflow and instrumental platform supporting the decision making process through clinical pathway of epilepsy patients undergoing surgical treatment. The platform is based on multimodal neuroimaging integration providing spatial landmarks ("aim" and "no go" areas) utilised during the key decision making stages: (1) generation of hypothesis about ictal onset zone, (2) decision making about implantation strategy, (3) developing implantation plan, (4) decision making and plan for resective surgery, (5) analysing post-surgical outcome. The crucial characteristic of the software tool in the core of our pipeline is high quality 3D visualisation of the brain and the landmarks. Here we present utilisation of our image processing pipeline for planning implantation of intracranial EEG (icEEG) electrodes. Methods: Starting point: (1) multimodal landmarks (e.g. reconstructed MEG/EEG source of epileptiform activity, white matter tracts, eloquent areas, lesions, defined as important for formulation of implantation strategy; (2) confirmed implantation strategy represented as set of brain areas that need to be sampled by icEEG and are accessible surgically, decision about dimensions and type of intracranial electrodes chosen for implantation. Procedure: The neurophysiologist and the neurosurgeon operate in the 3D environment carrying all neuroimaging information (landmarks for epileptogenic areas and eloquent cortex, crucial white matter tracts, brain anatomy, blood vessels, scalp) required to develop the implantation plan. The depth electrodes are modelled as 3D objects by specifying entry point on the scalp and target point in the suspected epileptogenic cortex (Figure 1a). The grid electrodes are modelled as segments of 3D surfaces shaped to fit the cortical surface and sized to the dimensions of the real grid electrode (Figure 1b). The resulted 3D models of the electrodes are uploaded on the neuronavigation system (Stealth, Medtronic ltd) to be available intra-operatively for guidance. Results: This pipeline was utilised for planning depth electrode placement in four patients. The post-operative comparison of the location of the implanted electrodes showed that the intended cortical areas were sampled. The observed deviation of the electrode placement from the plan was due to lack of imaging information carrying details important for surgical decision making at the stage of pre-operative planning (for example, skull). Conclusions: The utilisation of our instrumental pipeline for planning placement of intracranial electrodes demonstrated high potential for pre- and intra-operative use through high quality visualisation and variety of presented multimodal neuroimaging information available during surgery. Our experience showed that the pipeline presents an environment which is highly valuable for collaboration between epileptologists and neurosurgeons.