Abstracts

Rationale: It is well known that long term EEG monitoring significantly improves the diagnosis and classification of childhood epilepsy. However, long term EEG monitoring commonly requires hospitalization in a child unfriendly environment. We therefore designed a small wireless 24 channel EEG monitoring device and tested its quality and applicability in children. Methods: The system allows the simultaneous and continuous measurement of up to 24 unipolar EEG channels, with a common reference, in parallel with an additional ECG channel. Each signal is sampled at 1024Hz, and then sent via a 2.4 GHz wireless link to a receiver connected to a PC, where the data are visualized and stored for off-line processing. The range of the wireless device is up to 10m. An adaptor allows the direct interfacing with standard EEG DIN32 cables connected to commercially available electrode-caps. The power consumption of the system is 63mW, allowing for 3 days of continuous measurement on 2 high quality AA batteries. The total size of the packaged system is 8 x 10 x 3 cm and weighs only 177 g, and can be worn attached to the belt or arm. We compared the EEG signals obtained from a conventional EEG device with those of the new wireless device. Both systems were set up in parallel, with connections at the reference recording device, so that only one set of electrodes were attached to the subjects head. 33 children (age 3-20) were included. A standard EEG protocol was used, including eyes open/closed, hyperventilation and photic stimulation. Analysis included the following steps: 1. Fourier transform to each channel of both data sets during specific events. 2. Extract the power ratios for different frequency bands. 3. Statistical comparison of the ratios of each channel and each frequency band for the two systems. Results: The data showed a great concordance both in the time and frequency domain, with coherence coefficients being higher than 90% in all conditions. Also, the ratio of the power in the different frequency bands was found to be significantly similar. Conclusions: Our study shows that our miniature wireless EEG measurement device can be used in children and that the obtained EEG data are technically very comparable to traditional EEG monitoring. In a further step, our device will be used in home and school environments for longer monitoring of EEG in children with epilepsy.