Symptoms of Autoimmune Encephalitis
Autoimmune encephalitis typically presents as a polysyndromic disorder with acute or subacute onset (less than 3 months) featuring a combination of cognitive/behavioral changes, seizures, movement disorders, and autonomic dysfunction. 1
Temporal Pattern and Onset
- Acute to subacute presentation over days to weeks is the hallmark, with symptom duration typically less than 3 months 1
- A preceding viral infection, fever, or viral-like prodrome is common 1
- Hyperacute presentations (hours) are atypical and should prompt consideration of vascular causes 1
- Chronic presentations (>3 months) occur only with specific antibodies (LGI1, CASPR2, DPPX, GAD65) and otherwise suggest neurodegenerative disease 1
Core Clinical Manifestations
The diffuse brain inflammation in autoimmune encephalitis produces multifocal symptoms that vary by anatomical location, creating distinct clinical-anatomical syndromes: 1
Cognitive and Psychiatric Symptoms
- Altered mental status, decreased consciousness, lethargy, or personality change lasting ≥24 hours 2
- Rapidly progressive short-term memory deficits (especially in limbic encephalitis) 1
- Acute behavioral changes and psychosis that can mimic primary psychiatric disorders 1, 3, 4
- Cognitive dysfunction and confusion 1, 5
Seizures
- New-onset seizures are a major diagnostic criterion 2
- New-onset refractory status epilepticus (NORSE), either convulsive or non-convulsive 5
- Faciobrachial dystonic seizures (specific to LGI1-antibody encephalitis) 1
Movement Disorders
- Oromandibular dyskinesia (jaw-opening dystonia, grimacing) 1, 5
- Orofacial dyskinesias and abnormal movements 1, 5
- Dyskinesias and dystonia 4
- Choreoathetoid movements 6
Speech and Language Dysfunction
Autonomic Dysfunction
- Autonomic instability including blood pressure fluctuations, cardiac arrhythmias, hyperthermia 1, 5, 3
- Autonomic disturbances 6
Neurological Deficits
- New focal neurological findings 2
- Decreased level of consciousness progressing to catatonic states 3, 4
Antibody-Specific Stereotypical Presentations
While significant symptom overlap exists between all antibody types, certain patterns are recognized: 1
Anti-NMDAR Encephalitis
- Prominent psychiatric symptoms, cognitive dysfunction, seizures, orofacial dyskinesias, speech dysfunction, and autonomic instability 1
- Often presents initially as acute psychosis in young women 3
- Frequently associated with ovarian teratomas in females 1, 3
Anti-LGI1 Encephalitis
- Faciobrachial dystonic seizures (brief, frequent dystonic posturing of arm and face) 1
- Memory impairment 1
Anti-GABABR Encephalitis
Important Clinical Pitfalls
- Do not dismiss as primary psychiatric illness: Acute psychosis with seizures, movement disorders, or autonomic instability mandates evaluation for autoimmune encephalitis 3, 4
- Polysyndromic presentation is key: The combination of symptoms from multiple neurological domains (cognitive, motor, autonomic, seizures) distinguishes autoimmune encephalitis from focal processes 1
- Normal initial testing does not exclude the diagnosis: MRI, EEG, and even CSF can be normal early in the disease course 2, 5
- Consider paraneoplastic triggers: Patients with cancer history, smoking, elderly age, or unintentional weight loss are at higher risk for paraneoplastic autoimmune encephalitis 1
- Personal or family history of autoimmune disease increases risk for idiopathic autoimmune encephalitis 1
Diagnostic Criteria for Suspected Cases
When autoimmune encephalitis is suspected, the following features support the diagnosis: 2
Major Criterion:
- Altered mental status lasting ≥24 hours with no alternative cause 2
Minor Criteria (supporting features):