From cryogenic to on‐scalp magnetoencephalography for the evaluation of paediatric epilepsy

Abstract

Magnetoencephalography (MEG) is a neurophysiological technique based on the detection of brain magnetic fields. Whole‐head MEG systems typically house a few hundred sensors requiring cryogenic cooling in a rigid one‐size‐fits‐all (commonly adult‐sized) helmet to keep a thermal insulation space. This leads to an increased brain‐to‐sensor distance in children, because of their smaller head circumference, and decreased signal‐to‐noise ratio. MEG allows detection and localization of interictal and ictal epileptiform discharges, and pathological high frequency oscillations, as a part of the presurgical assessment of children with refractory focal epilepsy, where electroencephalography is not contributive. MEG can also map the eloquent cortex before surgical resection. MEG also provides insights into the physiopathology of both generalized and focal epilepsy. On‐scalp recordings based on cryogenic‐free sensors have demonstrated their use in the field of childhood focal epilepsy and should become a reference technique for diagnosing epilepsy in the paediatric population.

Where do we stand exactly with on‐scalp magnetoencephalography in the presurgical evaluation of refractory focal epilepsy?

“…Thus, if confirmed, OPM-MEG should become a reference tool for the management of RFE. 25 It could also extend the use of MEG to noncompliant populations 26 and to epilepsy diagnosis after inconclusive EEG, 27 and offer MEG access to more patients with RFE. Based on the above facts, OPM-MEG is closer from its clinical use than described in Bagić et al 1 despite the engineering obstacles/clinical tradeoffs.…”

“…Studies on large cohorts are mandatory to confirm its noninferiority compared with cryogenic MEG. 1,25 OPM-MEG advantages (wearability, lifespan/movement compliance, reduced cost) overcome the limitations of cryogenic MEG that has limited its worldwide adoption. Thus, if confirmed, OPM-MEG should become a reference tool for the management of RFE.…”

A Novel, Robust, and Portable Platform for Magnetoencephalography using Optically Pumped Magnetometers

“…This enables the recording of data during novel tasks (Boto et al, 2018; Rea et al, 2022) or even epileptic seizures (Feys, et al, 2023; Hillebrand et al, 2023). The adaptability to different head size/shape coupled with motion robustness (Feys & De Tiège, 2024) mean that, like EEG, OPM-MEG systems arewearable. However, unlike EEG, sensors do not need to make electrical contact with the head, making OPM-MEG considerably more practical than EEG in terms of both patient friendliness and set up time.…”

On-scalp magnetoencephalography can detect mesial temporal lobe epileptiform discharges

“…In such systems, magnetic field sensors require cryogenic cooling and are housed in a one-size-fits-all, commonly adult-sized, helmet to maintain thermal isolation (2–4 cm) from the scalp. This reduces the signal-to-noise ratio (SNR) and adaptability to the pediatric population 1 . Cryogenic MEG has demonstrated its ability to detect and localize epileptiform discharges emanating from deep brain structures such as the amygdala or the hippocampus thanks to simultaneous recordings with stereo-electroencephalography (SEEG) 2 .…”