What is the role of electroencephalogram (EEG) in patients with autism, particularly children and adolescents?

Role of EEG in Autism Spectrum Disorder

EEG should not be routinely performed in all children with autism, but is indicated when there is clinical suspicion of seizures, regression in language or cognitive skills, or specific historical features suggesting epilepsy. 1

When EEG is NOT Indicated

Routine screening EEG is not recommended for asymptomatic children with ASD. The evidence does not support universal EEG testing in autism without specific clinical concerns. 2

• EEG abnormalities occur in 20-25% of individuals with autism, but their presence does not change management in the absence of clinical seizures 1
• A 2025 systematic review found EEG abnormalities in 23-80% of ASD patients, but the relationship between these findings and specific ASD symptoms remains inconclusive 2
• The effectiveness of anticonvulsant treatment in children with EEG abnormalities but no clinical seizures is uncertain with limited supporting data 2

When EEG IS Indicated

Order EEG when any of the following red flags are present: 1

• History of regression, particularly language regression (to rule out Landau-Kleffner syndrome, which has a highly distinctive EEG abnormality) 1
• Staring spells or other paroxysmal events concerning for seizures 1
• Clinical seizures or suspected seizure activity 1
• Family history of seizures or epilepsy syndromes 1
• Dysmorphic features suggesting a genetic syndrome with epilepsy risk 1

Clinical Context of EEG Abnormalities

The high prevalence of EEG abnormalities in autism reflects underlying neurobiology but does not necessarily require intervention:

• Epileptiform discharges are found in 25-65% of children with ASD who undergo EEG, even without clinical seizures 3, 4
• These abnormalities are more common in temporal (30%), central (28%), and frontal (23%) regions 3
• One study found 36% of nonepileptic ASD patients had isolated epileptiform discharges 4
• In high-functioning autism, 31% showed EEG abnormalities, with only one patient developing seizures during follow-up 5

Practical Approach to Genetic Testing (More Relevant Than Routine EEG)

Genetic testing has higher diagnostic yield than routine EEG in autism evaluation: 1

• Chromosomal microarray is recommended as standard of care with 24% diagnostic yield 1
• G-banded karyotype has 2.5% yield 1
• Fragile X testing has 0.57% yield 1
• These tests identify treatable conditions and inform epilepsy risk better than screening EEG 1

Special Consideration: Refractory or Aggressive Cases

Consider EEG in treatment-refractory ASD, particularly with aggressive behaviors or medication failures: 4

• Most medications prescribed for ASD lower seizure threshold and increase side effects 4
• Identifying isolated epileptiform discharges may guide medication selection in patients who have failed stimulants, antidepressants, or antipsychotics 4
• This represents a precision medicine approach, though not yet standard practice 4

Common Pitfalls to Avoid

• Do not order routine EEG simply because a child has autism—this leads to unnecessary testing, false-positive results, potential sedation risks, and increased family anxiety 2
• Do not assume all EEG abnormalities require anticonvulsant treatment—treatment of subclinical epileptiform discharges in ASD lacks evidence 2
• Do not miss Landau-Kleffner syndrome by failing to obtain EEG in children with language regression—this is the one scenario where EEG findings directly change management 1
• Do recognize that epilepsy risk peaks around age 10 years in ASD and is associated with lower cognitive abilities, so maintain clinical vigilance during long-term follow-up 1, 5