FBDS, a pathognomonic manifestation of anti-LGI1 encephalitis, can be EEG negative, even though some patients show an abnormal EEG pattern consisting of a large slow wave in the frontopolar, frontal or central area preceding the tonic contraction of the contralateral arm by at least 700 ms [40,71,72]. Here, LGI1 is linked to viral encephalitis.