A 71-year-old woman presented to the emergency department with confusion and multiple alternating stereotyped unilateral jerks involving the arm and ipsilateral face (figure 1A, B; view supplementary video on the journal's website at http://pn.bmj.com). The jerky episodes started 2 weeks before but had increased progressively in frequency and number. During some attacks, there was loss of awareness and subsequent vocalisation. Routine blood tests and cerebrospinal fluid analysis were normal. MR scan of the …