In order to explain the reason why brainstem is responsible for the mental retardation in infantile spasms, the maximum energy criterion for burst-event identification in wall turbulence by wavelet analysis was used. It is found that the brainstem-channel of IS patients is very different from that of normal ones in response to stimulation and information transfer. According to the explanation of maximum energy criterion in the turbulence, it was noticed that mental retardation in IS is caused by the block of information transfer in the brainstem. Furthermore, the importance of this method for treatment evaluation is also indicated.