It frequently occurs in normally-developing children, usually between three and seven years of age, and is characterized by the gradual or sudden loss of the ability use or comprehend spoken language. It is a rare disorder, with approximately 160 cases diagnosed between 1957, when the syndrome was first identified, and 1990. The following are the most common indicators of Landau-Kleffner syndrome, however, individuals may experience symptoms differently. Spoken language is eventually affected, which may lead to complete loss of the ability to speak.
Some children develop their own method of communicating, such as with gestures or signs.
Approximately 80 percent of children with Landau-Kleffner syndrome have a history of one or more epileptic seizures that usually occur at night. All children with Landau-Kleffner syndrome have abnormal electrical brain wave activity on both sides of the brain. Language is the expression of human communication. It is a specific method, style, or form of communicating for individuals or groups of individuals. Hearing and intelligence usually are confirmed to be normal in children with Landau-Kleffner syndrome.