What are the typical symptoms of autoimmune encephalitis?

Autoimmune Encephalitis Symptoms

Autoimmune encephalitis typically presents with a polysyndromic constellation of neurological and psychiatric symptoms developing acutely or subacutely over less than 3 months, most commonly including cognitive impairment, behavioral/psychiatric changes, seizures, and movement disorders. 1

Temporal Pattern and Presentation

• Acute to subacute onset (duration less than 3 months) is the hallmark presentation 1
• A preceding viral infection, fever, or viral-like prodrome is common 1
• Hyperacute presentations are atypical and should prompt consideration of vascular etiology 1
• Chronic presentations (>3 months) are rare, seen mainly with LGI1, CASPR2, DPPX, and GAD65-antibody subtypes, and should raise suspicion for neurodegenerative disease 1

Core Clinical Features: The Polysyndromic Presentation

The diffuse multifocal brain inflammation in autoimmune encephalitis produces a characteristic polysyndromic presentation that distinguishes it from other neurological conditions 1:

Cognitive and Behavioral Symptoms

• Memory deficits (especially short-term memory impairment in limbic encephalitis) 2, 3
• Behavioral changes and psychiatric symptoms (present in 60% as the initial manifestation) 3
• Hallucinations (visual or auditory) 3
• Delusions and psychosis 3
• Catatonia 3
• Cognitive dysfunction and confusion 4, 5

Seizures and Status Epilepticus

• New-onset seizures are extremely common 1, 4, 5
• New-onset refractory status epilepticus (NORSE) is a major presentation 1
• Seizures can be convulsive or non-convulsive 1
• Faciobrachial dystonic seizures are pathognomonic for LGI1-antibody encephalitis 1

Movement Disorders

• Oromandibular dyskinesia (characteristic of NMDAR-antibody encephalitis) 1
• Hyperkinesia (involuntary movements) 6, 5
• Dystonia, chorea, and other abnormal movements 6
• Movement disorders frequently manifest throughout disease progression and can necessitate ICU admission 6

Speech and Autonomic Dysfunction

• Speech dysfunction (particularly in NMDAR-antibody encephalitis) 1
• Autonomic instability (a red flag for diagnosis) 3, 5
• Dysautonomia can be severe enough to require ICU-level care 1

Antibody-Specific Stereotypical Patterns

While significant symptom overlap exists between all antibody types, certain presentations are characteristic 1:

• NMDAR-antibody encephalitis: Oromandibular dyskinesia, cognitive/behavioral changes, speech dysfunction, autonomic dysfunction 1
• LGI1-antibody encephalitis: Faciobrachial dystonic seizures, frequent subclinical seizures 1
• However, these stereotypical patterns should not be relied upon exclusively, as all forms of AE show significant symptom overlap 1

Clinical Red Flags for Early Recognition

When evaluating psychiatric patients, specific "red flags" should prompt consideration of autoimmune encephalitis 3:

• Seizures (especially new-onset in psychiatric presentation) 3
• Catatonia 3
• Autonomic instability 3
• Hyperkinesia or abnormal movements 3
• Rapid progression of psychiatric symptoms with neurological signs 3

Anatomical Syndrome Categories

Symptoms vary according to the anatomical localization of inflammation 1:

• Limbic encephalitis: Memory impairment, behavioral changes, seizures 2
• Cortical/subcortical: Cognitive dysfunction, seizures, focal deficits 1
• Striatal: Movement disorders, behavioral changes 1
• Diencephalic: Autonomic dysfunction, sleep disturbances 1
• Brainstem: Cranial nerve deficits, ataxia 1
• Cerebellar: Ataxia, coordination problems 1
• Encephalomyelitis: Combined brain and spinal cord symptoms 1
• Meningoencephalitis: Meningeal signs with encephalopathy 1

Critical Pitfalls to Avoid

• One-third of patients are initially hospitalized in psychiatric wards, leading to delayed diagnosis 3
• The mean delay between symptom onset and antibody testing can be alarmingly prolonged (74 days in recent cases, 483 days historically) 3
• Using clinical red flags can reduce diagnostic delay by 58% 3
• Do not dismiss the diagnosis based on normal initial MRI or EEG—these can be negative despite active disease 1
• Psychiatric symptoms alone without neurological signs should still prompt consideration of AE when red flags are present 3