The causes of autistic regression are unknown, but it is suspected that subclinical epilepsy may play a role in some children. In other genetically susceptible children, an infectious or even emotionally-taxing event may serve as triggers. Until an adequate number of children have been referred for investigation close in time to the regression, its causes will remain speculative. The course of the regression is a more or less prolonged developmental plateau, with or without fluctuations, then improvement, but almost never full recovery. III and IV sleep reveal subclinical epilepsy in a greater number of children.
All seizure types can occur.
Echolalia and the use of memorized scripts are compensatory mechanisms in children who rely on an excellent verbal memory to circumvent difficulty in word retrieval, responding to open-ended questions, and the organization of coherent discourse. What is universally impaired in autism and distinguishes autism from specific developmental language disorders is very impaired pragmatics, that is, the conversational use of language. Except for mildly affected children with so-called Asperger syndrome, children with autism acquire language late. Those who remain nonverbal tend to have persistent severe comprehension deficits and to be mentally deficient. Other Symptoms Children with autism may have motor deficits such as hypotonia, clumsiness, toe walking, and repetitive stereotyped movements and activities, as well as sensory symptoms such as atypical perception of somatosensory, visual, auditory, gustatory, and olfactory signals.