From the Guidelines
The diagnosis of autoimmune encephalitis should be based on a combination of clinical evaluation, brain MRI and/or EEG, lumbar puncture, and blood tests, as outlined in the best practice recommendations for diagnosis and acute management 1. To evaluate the likelihood of autoimmune encephalitis, the following steps should be taken:
- Evaluate the likelihood of AE relative to the patient’s clinical picture
- Perform brain MRI and/or EEG to look for focal or multifocal brain abnormality
- Perform lumbar puncture to support inflammatory aetiology and rule out infective/neoplastic causes, including testing oligoclonal bands, IgG index, IgG synthesis rate, and neuronal autoantibodies in the cerebrospinal fluid (CSF) 1
- Send blood tests to rule out other potential causes guided by neuroanatomical and clinical data, including testing neuronal autoantibodies in the serum 1 The diagnostic criteria for autoimmune encephalitis include clinical features, such as subacute onset of memory deficits, altered mental status, psychiatric symptoms, seizures, movement disorders, or autonomic dysfunction, as well as CSF findings, MRI abnormalities, and EEG changes 1. Specific antibody testing is crucial and includes testing for antibodies against neuronal cell-surface antigens and intracellular antigens 1. A definite diagnosis requires detection of specific autoantibodies in CSF or serum, while a probable diagnosis can be made with typical clinical features, CSF pleocytosis, and supportive MRI or EEG findings even without antibody detection 1. Early diagnosis is essential as prompt immunotherapy significantly improves outcomes by targeting the underlying autoimmune process before irreversible neuronal damage occurs 1.
From the Research
Diagnostic Criteria for Autoimmune Encephalitis
The diagnostic criteria for autoimmune encephalitis (AIE) involve a combination of clinical, radiological, and laboratory findings. According to 2, the 2016 AE guidelines permit autoimmune causation assessment in subacute encephalopathy and are highly specific. The criteria include:
- Subacute onset
- Memory deficits, altered mental status, or psychiatric symptoms
- At least one supportive feature, such as:
- New focal objective CNS finding
- New-onset seizures
- Supportive MRI findings
- CSF pleocytosis
Clinical Presentation
AIE presents with a diverse range of symptoms, including altered mental status, memory deficits, psychiatric symptoms, and seizures. As reported in 3, patients with AIE often have abnormal neuroimaging and cerebrospinal fluid (CSF) findings, such as T2-weighted hyperintensities in cortical/mesio-temporal regions on MRI and delta brush wave patterns on EEG.
Laboratory Findings
The diagnosis of AIE is supported by the presence of specific autoantibodies in serum and CSF. According to 2, the most common autoantibodies detected in patients with definite AIE are LGI1, NMDA-R, and high-titer GAD65. CSF findings may include lymphocytosis, elevated glucose, and oligoclonal bands, as reported in 3.
Imaging Findings
Imaging findings in AIE can be variable, but characteristic findings within limbic structures suggestive of autoimmune encephalitis can be a key step in alerting clinicians to the potential diagnosis. As reviewed in 4, neuroimaging plays a crucial role in the diagnostic work-up of AIE.
Management
Early recognition and treatment of AIE are paramount to improve outcomes and achieve complete recovery. According to 5 and 6, treatment options include intravenous immune globulin, steroids, plasmapheresis, and rituximab. A prompt and appropriate clinical work-up is essential to ensure timely management and improve patient outcomes.