• EEG
• EPILEPSY
• NEUROPHYSIOLOGY

Einstein said, ‘Everything should be made as simple as possible, but not simpler.’ He undoubtedly recognised that, across scientific disciplines, there is an endless need to classify. Classification strives to make sense out of chaos—allowing us to identify more easily any similarities across different groups. Einstein also said, ‘Information is not knowledge,’ and, ‘The only source of knowledge is experience.’ While we can be pleased to place three Einstein quotations into the first paragraph of a Practical Neurology article, we have only transmitted information. To learn what Einstein meant by these salutary rejoinders, we need context and ‘experience’.

The International League Against Epilepsy (ILAE) 2017 classification of seizure types divides seizures into three major groups: focal onset, generalised onset and unknown onset (box 1).1 Focal-onset seizures are conceptualised as originating within networks limited to one hemisphere. Generalised-onset seizures originate at some point within, and rapidly engage, bilateral networks. The unspoken subtext, too controversial to make explicit, is that all seizures begin somewhere and that all must have a focal onset. Indeed, the modification of the ILAE classification for neonates takes the next step and regards all seizures as having a focal onset, completely discarding the concept of generalised onset.2 In 2024, another ILAE task force suggested removing the prefix ‘onset’, though keeping the terms focal, generalised …