![]() On EEG pop is marked by a single electrode showing a very sudden, steep upslope with a slower downslope and absolutely no field. A common such finding is electrode pop, caused most often by a loose electrode. In the example below, the notch filter is not on, and the Fp1 electrode is likely not on quite right, leading to a lot of electrical interference.Įlectrodes themselves can give artifact as well, usually in the setting of them becoming loose over time or getting bumped by things in the environment. Electrical artifact is a very fast, very monotonous activity, and you can use the notch filter to selectively remove all the EEG activity at 60Hz (this won't affect your interpretation of the signal, as no cerebral activity is that fast on scalp EEG). ![]() One notable point about tongue movement artifact is that it is reproducible-you can ask the patient to move it, or to say "la la la" (aka a lingual phoneme) to see if the same pattern is brought out on the EEG.Įlectrical artifact most commonly arises from interference from the 60 Hz electrical activity (in the USA 50 Hz in Europe and elsewhere) that that runs through wires so, it can be caused by anything from an electrical appliance to a cell phone charging, though most modern EEG equipment is quite good at minimizing it. Notice how, on the example below, all the tracings have essentially the same movement-this is much too organized for something like slow wave sleep, and while ictal patterns can certainly lead to such rhythmicity, there is no evidence on this single page of the evolution across time or location that characterize seizures. It arises from the movement of the tongue, and appears as slower, diffuse delta frequency activity. Hypoglossal artifact is often but not requisitely seen with chewing artifact. Just be careful not to mix it up with generalized periodic fast activity, which tends to be slightly slower (beta frequency) and lower in amplitude. It is quite easy to characterize with video studies, as you can just look at the video to correlate, but even without video studies chewing artifact does not usually share a close morphology with any other important physiologic activity. ![]() Chewing artifact is really just muscle artifact from the temporalis muscle, and is marked by sudden onset, intermittent bursts of generalized very fast activity (muscle artifact). Chewing and tongue (hypoglossal) artifact are rather hard to miss on EEG.
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