Authors :
Mark Cook, MD, PhD – St Vincent's Health, Australia
Presenting Author: amy Halliday, MD – St. Vincent's Hospital
Lisa Gillinder, MD – School of Medicine, University of Queensland, St Lucia, Queensland, Australia
Ramya Raghupathi, MD – Penn Neuroscience Center
Rationale:
Seizure lateralisation has traditionally been considered stable in patients with focal epilepsy, especially those classified as having unilateral onset. However, chronic intracranial EEG monitoring, such as that reported by King-Stevens et al. using the NeuroPace RNS System, has shown that lateralisation can change over time. Reliable determination requires long-term recording, as brief inpatient monitoring may be insufficient. Prior studies suggest that at least three to four months of continuous data are needed to characterise seizure patterns accurately. This study assessed seizure lateralisation stability over six months using the Minder iCEM system.
Methods:
Ten patients with focal epilepsy and prior EEG-confirmed unilateral seizure onset were implanted with the Minder iCEM system. The device includes a single lead with four electrodes, two over each hemisphere, positioned posterior to the vertex. It continuously recorded EEG signals, transmitted via Bluetooth® to a smartphone, with cloud-based storage. Implantation was performed under general anaesthesia using a minimally invasive technique. Seizures were visually reviewed and lateralised by board-certified US electrophysiologists blinded to clinical data. Lateralisation was analysed at 1, 3, and 6 months after implantation. Ethics approval was obtained from the St Vincent’s Hospital Melbourne HREC (HREC158/19) and the study was registered (ACTRN12619001587190).
Results:
Of the ten subjects, five maintained a consistent right-sided seizure onset across all time points. Two initially had right-sided seizures but developed increasing left-sided events. One transitioned from right-sided to exclusively left-sided seizures by six months. Another showed left-sided onset that became bilateral. One patient remained stable with left-sided onset. In total, four of ten patients (40%) exhibited a change in lateralisation pattern over the six-month period. These results suggest that seizure onset, even in apparently unilateral cases, may evolve with time.
Conclusions:
The Minder iCEM system enables long-term monitoring of seizure lateralisation in a minimally invasive format. This study confirms that lateralisation can shift within months in a substantial proportion of patients. These findings underscore the importance of extended EEG monitoring when evaluating seizure foci, especially in the context of surgical or device-based treatment for drug-resistant epilepsy.
Funding:
This study was funded by Epiminder Ltd.