Implementing Physiologist-Led Electrical Source Imaging (ESI) in the Presurgical Evaluation of Drug-Resistant Epilepsy: A Comparative Observational Study

Background

Drug-resistant focal epilepsy affects approximately one-third of individuals with epilepsy, many of whom may benefit from surgery. Successful outcomes depend on accurate localisation of the epileptogenic zone (EZ) during presurgical evaluation. Electrical Source Imaging (ESI) is a non-invasive neurophysiological technique that estimates the cortical origin of epileptiform activity from scalp EEG recordings. Although ESI has been validated in research settings, its clinical implementation remains limited, partly due to the need for specialist expertise. In most UK centres, ESI is consultant-led and performed on an ad hoc basis. Expanding ESI competency among clinical physiologists could enhance service accessibility, reduce turnaround times, and improve efficiency.

Aim

To evaluate the feasibility, accuracy, and efficiency of a physiologist-led ESI workflow in comparison with the existing consultant-led service in the presurgical evaluation of patients with drug-resistant focal epilepsy.

Methods

This single-centre retrospective observational study will include patients who have undergone presurgical evaluation with available interictal EEG recordings and definitive outcome data (SEEG-defined seizure onset zone and/or surgical resection area and postoperative seizure outcome). Both the consultant and the clinical physiologist will independently perform ESI analyses on the same patient cohort using BESA software on low- and high-density EEG datasets. Results will be compared for localisation accuracy, defined by concordance with SEEG-defined SOZ or resected area. Statistical analyses will include Cohen’s kappa for inter-rater agreement, McNemar’s test for paired categorical comparisons, and logistic regression models to explore predictors of concordance. Efficiency metrics such as turnaround time and reporting latency will also be evaluated using a time-log framework.

Expected outcomes

The study will quantify the concordance between consultant and physiologist-generated ESI results and assess differences in analysis time and workflow efficiency. It will also provide real-world data on the feasibility of implementing physiologist-led ESI within a tertiary epilepsy centre.

If physiologist-led ESI demonstrates comparable accuracy and improved efficiency relative to consultant-led analysis, this could support wider clinical adoption of ESI, reduce bottlenecks in presurgical evaluation, and establish a scalable model for multidisciplinary service delivery within the NHS.

Outputs

None yet as the research has not started yet.