Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Landau-Kleffner syndrome ?
    ### Response:
    Landau-Kleffner syndrome (LKS) is a rare, childhood neurological disorder characterized by the sudden or gradual development of aphasia (the inability to understand or express language) and an abnormal electro-encephalogram (EEG). The disorder usually occurs in children between age 2 and 8.
    