When is an electroencephalogram (EEG) recommended in patients presenting with psychosis?

EEG in Psychosis: When to Order

EEG is not routinely recommended for new onset psychosis without neurologic deficits, but should be strongly considered when there is suspected seizure activity, altered consciousness, encephalopathy, or when the clinical presentation suggests autoimmune encephalitis. 1

Primary Indications for EEG in Psychotic Presentations

Suspected Seizure-Related Psychosis

• Order emergent EEG when you suspect nonconvulsive status epilepticus or subtle convulsive status epilepticus in patients with altered mental status and psychotic features 1
• Consider EEG when psychosis follows a cluster of seizures, as postictal psychotic events can occur 12-72 hours after the last seizure and may mimic primary psychiatric disorders 2
• EEG is essential to exclude subclinical status epilepticus in encephalopathic patients presenting with psychotic symptoms 1

Autoimmune Encephalitis Evaluation

• Perform EEG when autoimmune encephalitis is in the differential diagnosis, particularly when psychosis is accompanied by altered consciousness, seizures, or movement disorders 1
• EEG can provide evidence of focal or multifocal brain abnormality when MRI is negative, supporting encephalitis over metabolic encephalopathy 1
• Specific findings like extreme delta brush suggest NMDAR-antibody encephalitis, while frequent subclinical seizures are common in LGI1-antibody encephalitis 1
• A normal EEG can support primary psychiatric disorders when investigating patients with isolated new psychiatric symptoms, helping differentiate from autoimmune encephalitis 1

Persistent Altered Consciousness

• Order EEG for persistent altered consciousness following any seizure activity, as 25% of patients with generalized convulsive status epilepticus have continuing electrical seizures despite cessation of convulsive movements 1
• EEG is the definitive test for detecting ongoing electrical seizure activity that may cause neuronal injury even without visible convulsions 1

When EEG is NOT Routinely Indicated

Uncomplicated First-Episode Psychosis

• Do not order routine EEG for new onset psychosis without neurologic deficits or altered consciousness 1
• The American College of Emergency Physicians found inadequate literature supporting neuroimaging or EEG for new onset psychosis without neurologic deficits in the ED setting 1
• Individual risk factor assessment should guide the decision, focusing on presence of focal neurologic signs, seizure history, or altered consciousness 1

Primary Psychiatric Presentations

• EEG is not useful for detecting clinically relevant abnormalities in straightforward psychotic presentations without neurologic features 3
• When the clinical picture clearly suggests primary psychiatric illness without encephalopathy or seizure activity, proceed with psychiatric evaluation and treatment without EEG 1

Prognostic Value of EEG Findings

When EEG is Performed

• Abnormal baseline EEG in first-episode psychosis predicts poorer outcomes: only 58.3% of patients with dysrhythmia achieved remission at 1 year versus 90.5% with normal EEG 3
• Dysrhythmic EEG is independently associated with persistent positive and negative symptoms and poorer psychosocial functioning at 5-year follow-up 4
• Patients with normal EEG had 61.1% reduction in negative symptoms versus 0% in those with dysrhythmia 3

Practical Algorithm for Decision-Making

Order EEG if ANY of the following are present:

• Altered level of consciousness or encephalopathy 1
• Known seizure disorder or witnessed seizure activity 1, 2
• Psychosis developing 12-72 hours after seizure cluster 2
• Clinical features suggesting autoimmune encephalitis (movement disorders, autonomic instability, memory impairment) 1
• Atypical presentation with fluctuating consciousness 1
• Failure to respond to standard antipsychotic treatment with persistent encephalopathy 1

Do NOT order routine EEG if:

• Clear first-episode psychosis without neurologic signs 1
• Normal level of consciousness 1
• No seizure history or witnessed seizure activity 1
• Typical psychiatric presentation without encephalopathy 1

Critical Pitfalls to Avoid

• Do not delay EEG when nonconvulsive status epilepticus is suspected, as ongoing electrical seizures cause neuronal injury despite absence of convulsive movements 1
• Recognize that postictal psychotic events can occur up to 72 hours after the last seizure and may be mistaken for primary psychiatric illness 2
• Remember that a normal EEG does not exclude autoimmune encephalitis, but supports primary psychiatric disorders when other features are absent 1
• Be aware that EEG availability in emergency settings averages 3 hours from request to interpretation, which may limit utility for time-critical decisions 1
• Neurologic consultation before obtaining EEG is reasonable given that interpretation requires specialized expertise 1