Language heterogeneity and regression in the autism spectrum disorders—Overlaps with other childhood language regression syndromes

Some third of parents of children on the autism spectrum report that their toddler’s language regressed, usually insidiously, or stagnated during a prolonged plateau. Regression was associated with loss of sociability, interest in toys, and other behavioral skills, without motor regression. After months or longer, language usually returns, but variably severe autistic features persist. Nonverbal cognitive skills may or may not be affected. Some parents recall some antecedent nonspecific illness or stressor like the absence of a parent, a move, or the birth of a sibling. Occasionally, regression seems temporally related to an epileptic seizure, suggesting an overlap with acquired epileptic aphasia (Landau–Kleffner syndrome—LKS) in which language regression is associated with either clinical seizures or subclinical perisylvian temporo-parietal epileptiform EEG activity. LKS onset peaks at 4–6 years, autistic regression before age 2 years and is infrequently associated with seizures or an epileptiform EEG, except in the rare case of disintegrative disorder, a late global autistic regression which, like LKS, may be associated with electrical status epilepticus in slow wave sleep. Mute or dysfluent children with LKS, autism, or developmental language disorders are unable to decode or have difficulty decoding acoustically presented language (speech). They are at higher risk for epilepsy than fluent children with the typically aberrant language of verbal children with autism. The pathogenesis of language regression remains unknown because autistic toddlers are rarely studied at the time of language regression so that no empirically validated effective treatment has yet been devised.