Miscellaneous benign myoclonus of infancy and shuddering attack true Benign myoclonus of infancy and shuddering attacks are both benign (self limiting) variants of normal behaviour in infants and may be related conditions with differing durations of attacks. These attacks typically have onset from 4 months of age and can persist up to the age of 6-7 years, with a remitting and relapsing course. https://www.ncbi.nlm.nih.gov/pubmed/11292215