Landau Kleffner syndrome (LKS) is a rare epilepsy. It occurs in children usually between the ages of three and nine years and is characterised by loss of language skills and silent electrical seizures during sleep. It may be associated with convulsive seizures and additional difficulties with behaviour, social interaction, motor skills and learning. It is not usually life-threatening, but can impact greatly on quality of life unless it responds well to treatment. It occurs in approximately one child in a million. The disease is more common in boys and does not usually run in families.