Focal, generalised epilepsy or both?

A 29-year-old woman presented with a witnessed convulsion, with semiology consistent with a focal-to-bilateral tonic-clonic seizure. Routine EEG supported a syndromic diagnosis of idiopathic generalised epilepsy with photosensitivity. We discuss the clinical utility of seizure semiology, highlighting the caveat that over-reliance or sole reliance on the ictal semiology may result in an erroneous diagnosis of focal epilepsy in someone with a generalised epilepsy.