Table 2 Consensus criteria for autoimmune encephalitis and autoimmune psychosis, as well as red and yellow flag symptoms for autoimmune encephalitis in psychiatric patients [73,74,75].

1. Subacute onset (rapid progression of less than 3 months) of working memory deficits, altered mental status, or psychiatric symptoms

Yellow flag symptoms/findings:

Possible autoimmune psychosis:

2. At least one of the following:

◦ Decreased levels of consciousness

Psychotic symptoms of abrupt onset (rapid progression of <3 months) with at least one of the following:

◦ New focal neurological findings

◦ Abnormal postures or movements (orofacial, limb dyskinesia)

◦ Currently or recently diagnosed with a tumor

◦ Seizures

◦ Autonomic instability

◦ Movement disorder (catatonia or dyskinesia)

◦ CSF pleocytosis

◦ Focal neurological deficits

◦ Adverse response to antipsychotics, raising suspicion of neuroleptic malignant syndrome

◦ MRI suggestive of encephalitis

◦ Aphasia or dysarthria

◦ Severe or disproportionate cognitive dysfunction

3. Exclusion of alternative causes

◦ Rapid progression (despite therapy)

◦ A decreased level of consciousness

◦ Hyponatremia

◦ Seizures

◦ Catatonia

◦ Autonomic dysfunction (abnormal or unexpectedly fluctuant blood pressure, temperature, or heart rate)

◦ Headache

Probable autoimmune psychosis:

◦ Other autoimmune diseases (e.g., thyroiditis)

Current psychotic symptoms of abrupt onset (rapid progression of <3 months) with at least one of the seven clinical criteria listed above

Red flag symptoms/findings:

and at least one of the following:

◦ CSF pleocytosis

◦ Bilateral brain abnormalities on T2-weighted FLAIR MRI highly restricted to the medial temporal lobes

◦ CSF pleocytosis or CSF-specific oligoclonal bands

or two of the following:

◦ Seizures/faciobrachial dystonic seizures

◦ “Encephalopathic” EEG changes (i.e., spikes, spike-wave activity, or rhythmic slowing, focal changes, or extreme delta brush)

◦ Suspected malignant neuroleptic syndrome

◦ CSF-specific oligoclonal bands or increased IgG index

◦ MRI abnormalities (mesiotemporal hyperintensities, atrophy pattern)

◦ The presence of a serum neuronal antibody detected by cell-based assay

◦ After exclusion of alternative diagnoses.

◦ EEG alterations (slowing, epileptic activity or extreme delta brush)

Definite autoimmune psychosis:

Probable autoimmune psychosis with

◦ IgG class neuronal antibodies in CSF.