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 epilepsy or genetic syndromes associated with seizures 1
- Dysmorphic features suggesting an underlying genetic syndrome 1
Clinical Context of EEG Abnormalities
The high prevalence of EEG abnormalities in autism reflects underlying neurobiology but does not necessarily warrant treatment:
- 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 (24%) regions 3
- The presence of isolated epileptiform discharges without clinical seizures does not automatically require anticonvulsant therapy 2
Special Considerations for Treatment Planning
Consider EEG in refractory ASD cases before medication trials, particularly when planning stimulants, antidepressants, or antipsychotics: 4
- Most medications prescribed for ASD lower seizure threshold and increase side effects 4
- 36% of nonepileptic ASD patients aged 4-25 years showed isolated epileptiform discharges on EEG 4
- This is particularly relevant for patients with aggressive behaviors or those who have failed previous medication attempts 4
Long-term Monitoring
Children with documented EEG abnormalities require ongoing medical follow-up: 3, 5
- Even in high-functioning autism without clinical seizures, 25-31% may have epileptiform abnormalities 5
- The risk of developing clinical epilepsy during follow-up exists, though the exact rate is unclear 5
- Lower IQ and more severe autism symptoms correlate with higher epilepsy risk, though EEG abnormalities occur across the functional spectrum 1, 5
Genetic Testing Takes Priority Over EEG
When evaluating a child with ASD, chromosomal microarray and targeted genetic testing should be performed before considering routine EEG: 1
- Chromosomal microarray has a 24% diagnostic yield and is recommended as standard of care 1
- Genetic mutations that increase epilepsy risk can be identified before seizures develop, allowing for more intensive monitoring 1
- Specific genetic syndromes (e.g., 15q11-13 duplications, 16p11.2 CNVs, TSC) confer high epilepsy risk and may warrant closer EEG surveillance 1
The key clinical pitfall is ordering EEG reflexively in all autism cases rather than targeting it to children with specific clinical indicators. This leads to unnecessary testing, false-positive results, potential sedation risks in young children, and does not improve outcomes in asymptomatic patients. 2