Potential of ⁴He OPM-MEG for detecting interictal epileptic activity: A comparison with SQUID-MEG

Conventional magnetoencephalography (MEG) based on superconducting quantum interference devices sensors (SQUIDs) is the only widely used MEG system in both clinical and research settings. However, it has limitations that hinder its widespread deployment. Optically pumped magnetometers (OPMs) offer several advantages over SQUIDs, particularly for epilepsy studies: lightweight and flexible, OPMs can be integrated into adaptable motion-tolerant headsets, enabling recordings during seizures or natural head movements, and potentially enhancing the detection of interictal epileptiform discharges (IEDs). In the present study, we assess the capabilities of a 5-sensor MEG system with helium OPMs (⁴He-OPMs) in detecting IEDs.

First, we compare the performance of SQUID-MEG and ⁴He-OPM-MEG in a group of 7 patients. Second, we perform combined intra-cerebral (SEEG) ⁴He-OPM-MEG and SQUID-MEG recordings in a single patient to demonstrate the ability of both systems to detect IEDs originating from deep brain structures.

The key finding is that both the SQUID-MEG and the ⁴He-OPM-MEG prototype, with a very limited number of sensors, successfully captured interictal epileptic activity in 5 of the 7 patients. This activity was clearly detectable and exhibited the characteristic morphology, with strikingly similar time courses between ⁴He-OPM-MEG and SQUID-MEG signals. Using combined SEEG and OPM-MEG recordings, we obtained the first direct validation of the ability of ⁴He OPM sensors to record epileptic activities originating from deep structures.

These results strongly support the clinical adoption of a lightweight, high-sensitivity, whole-head OPMs-MEG system, offering new perspectives for epilepsy diagnostics and beyond, and enabling the democratization and spread of MEG in clinical and research settings.

Magnetoencephalography is a noninvasive neuroimaging technique that has been shown to improve surgical outcomes in epileptic patients. However, its use remains limited due to several constraints, which could be overcome by a new generation of sensors: the optically pumped magnetometers (OPMs). Here, we validate the ability of OPM sensors to record epileptic brain activity in a regular clinical setup and thanks to simultaneous intracerebral recordings. These sensors open new venues for the widespread application of magnetoencephalography in the management of epilepsy, as well as for fundamental neuroscience.