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The phase locking index (PLI) was introduced to quantify in a statistical sense the phase synchronization of two signals. It has been commonly used to process biosignals. In this paper, we analyze the PLI for measuring the interdependency of cortical source signals (CSSs) recorded in the Electroencephalogram (EEG). The main focus of the analysis is the probability density function, which describes the sensitivity of the PLI to the joint noise ensemble in the CSSs. Since this function is mathematically intractable, we derive approximations and analyze them for a simple analytical model of the CSS mixture in the EEG. The accuracies of the approximate probability density functions (APDFs) are evaluated using simulations for the model. The APDFs are found sufficiently accurate and thus are applicable for practical intents and purposes. They can hence be used to determine the confidence intervals and significance levels for detection methods for interdependencies, e.g., between cortical signals recorded in the EEG.

SummaryObjectivesMany patients thought to have temporal lobe epilepsy, are evaluated for surgical treatment. Decision-making in epilepsy surgery is a multidisciplinary, phased process involving complex diagnostic tests. This study reviews the literature on the value of different tests to decide on whether to operate.MethodsArticles were selected when based on the consensus decision whether to perform temporal lobe surgery, or on the consensus localization or lateralization of the epileptic focus. The articles were scrutinized for sources of bias as formulated in methodological guidelines for diagnostic studies (STARD).ResultsMost studies did not fulfill the criteria, largely because they addressed prognostic factors in operated patients only. Ten articles met our inclusion criteria. In most articles, a single test was studied; SPECT accounted for five papers. Unbiased comparison of the results was not possible.ConclusionSurprisingly little research in epilepsy surgery has focused on the decision-making process as a whole. Future studies of the added value of consecutive tests are needed to avoid redundant testing, enable future cost-efficiency analyses, and provide guidelines for diagnostic strategies after referral for temporal lobe epilepsy surgery.

Epilepsy is a chronic brain disease with unpredictable recurrence of seizures. It is not a curable disease, and the treatment for it is long and often difficult for the patient. Over the years, healthcare professionals have developed a set of guidelines for treating epilepsy. Improving patient’s care is of great importance to Kempenhaeghe. This report describes a project to analyze and interpret epilepsy-related information, and to design a system that provides valuable feedback for healthcare professionals and patients to improve treatment via the use of visualization techniques. A formal model of the epilepsy information and guidelines is developed, and coupled with a prototype. The prototype supports checking conformance of doctors’ prescriptions against the epilepsy guidelines, checking of future prescriptions for conformance and patient-specific applicability, and exploring patient’s care journey with epilepsy. This is supported with visualizations that provide the user with immediate data interpretation and feedback. The project lists also several suggestions for future improvements.