https://tacanow.org/family-resources/seizures/

When determining if a medical condition causing or contributing to your child's speech issues, it is important to evaluate for seizures. Seizure activity that occurs in the area of the brain that supports speech and language, will cause your child will experience communication difficulties.

Also, it is important for parents to understand that seizures are common to autism. In fact, it is estimated that up to 45% of individuals with ASD are affected by seizures by the time they reach adulthood, and up to 60% have subclinical electrical dis-charge—many without any obvious clinical seizures.

Unfortunately, seizures often go undiagnosed in individuals with autism. This happens for a number of reasons, but mainly because the symptoms of seizures mimic symptoms that we typically associate with autism, such as stimming, sleep issues, and motor tics.

Seizures may also be missed during the initial evaluation process. This can occur if your child's neurologist relies soley on the results of a 30-minute EEG when checking for seizure activity. For example, unless your child happens to have a seizure during the 30-minute period they are hooked up to the EEG equipment, the doctor is likely to conclude that seizures aren't an issue. But, what if your child only has seizures while they're sleeping? For this reason, we recommend that every child with autism have at least a 24-hour EEG.

You can read more about seizures here.