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Magneto- and Electroencephalography (MEG/EEG) are important techniques for the diagnosis and pre-surgical evaluation of epilepsy. Yet, in current cryogen-based MEG systems the sensors are offset from the scalp, which limits the signal-to-noise ratio (SNR) and thereby the sensitivity to activity from deep structures such as the hippocampus. This effect is amplified in children, for whom adult-sized fixed-helmet systems are typically too big. Moreover, ictal recordings with fixed-helmet systems are problematic because of limited movement tolerance. Optically Pumped Magnetometers (OPMs) can be placed directly on the scalp, thereby improving SNR and consequently the sensitivity to, and localisation accuracy of, epileptiform activity. In addition, recording during seizures becomes feasible with these wearable sensors.We aimed to demonstrate these advantages of OPMs in a clinical population. Three adults with known weak sources of interictal epileptiform discharges (IEDs), along with three children with focal epilepsy and one adult with frequent seizures underwent MEG recordings using a 12-channel OPM-system and a 306-channel cryogen-based whole-head system. Performance of the two systems was compared in terms of IED-rate and SNR.In one patient the OPMs detected IEDs that were not found with the SQUID-system. In one patient the spike yield was higher for the OPM data (9.00 versus 6.76), with negligible difference in SNR compared to the SQUID data (3.85 versus 3.93; U = -2.86, d = -0.14). This was also the case for a patient with a spike yield that was comparable to that for the SQUID data (after accounting for unilateral coverage with the OPMs; SNR 4.47 versus 4.57; U = -3.81, d = -0.14). For one patient the spike yield (11.03 versus 24.50) and SNR (4.39 versus 4.05; U = 9.53, d = -0.36) were both lower for the OPMs. In two patients no IEDs were found with either system. Importantly, the wearability of OPMs enabled the recording of seizure activity in a patient with hyperkinetic movements during the seizure. The observed ictal onset and semiology were in agreement with previous video- and stereo-EEG recordings.Overall, OPM data were very much comparable to those obtained with a cryogenic system: OPMs outperformed SQUIDs for two of the four patients with IEDs, with either a higher spike yield, or an ability to detect IEDs that were not observable in the SQUID data. For three patients the SNRs of IEDs were (slightly) lower in the OPM data than in the SQUID data, but with negligible effect sizes for two of these patients. The relatively cheap technology, in combination with reduced running and maintenance costs, means that OPM-based MEG could be used more widely than current MEG systems, and may become an affordable alternative to scalp EEG, with the potential benefits of increased spatial accuracy, reduced sensitivity to volume conduction/field spread, and increased sensitivity to deep sources. Wearable MEG thus provides an unprecedented opportunity for epilepsy, and given its patient-friendliness, we envisage that it will not only be used for presurgical evaluation of epilepsy patients, but also for diagnosis after a first seizure.

Zowel EEG als MEG kan behulpzaam zijn om de bron van focale epilepsie te lokaliseren. Deze technieken zijn met name interessant als er geen MRI-afwijking is, of de MRI-afwijking niet past bij de aanvallen. Beide technieken hebben voor- en nadelen en hebben een eigen plaats in het prechirurgische traject naar epilepsiechirurgie verworven. In deze bijdrage worden de principes en toepassing van MEG- en EEG-bronlokalisatie en de meest recente ontwikkelingen hiervan besproken.

Objective: Many individuals with stroke cannot open their affected hand in a functional way: they either produce insufficient hand opening, or achieve hand opening while flexing their wrist. Insufficient hand-opening in post-stroke individuals can be improved by applying functional electrical stimulation (FES) to finger/thumb extensors. However, how to reduce the coupling between finger extension and wrist flexion is still unknown. Both FES to wrist extensors and a wrist-hand orthosis (WHO) can assist holding the wrist in a close-to-neutral position. This may or may not improve purposeful use of the paretic arm, depending on how it will interfere with hand opening. Therefore, this study investigated how using either FES or WHO to maintain the wrist in a close-to-neutral position will impact the FESassisted hand opening. Methods: We recruited twelve individuals with moderate to severe stroke to participate. They performed maximal hand opening with or without assistance from FES/WHO. Hand opening distance and wrist flexion angle were measured. Results: Our results demonstrated that FES applied to the finger extensors resulted in a trend of larger opening distance (p 0.2); however, a trend of reduced wrist flexion angle (p=0.057) when using WHO combined with FES. Conclusion: These results suggest that combined FES and WHO should be considered when designing interventions or devices to enhance hand opening in individuals with stroke.