Autoimmune encephalitis (AIE) is a type of encephalitis.
AIE is one of the most common causes of noninfectious encephalitis.
AIE can be triggered by tumors, infections, or may be cryptogenic.
Its neurological manifestations can be either acute or subacute and usually develops within six weeks.
The clinical manifestations include behavioral and psychiatric symptoms, autonomic disturbances, movement disorders, and seizures.
AIE can result from a number of autoimmune diseases including:
Rasmussen encephalitis Systemic lupus erythematosus Behçet’s disease Hashimoto’s encephalopathy Autoimmune limbic encephalitis Sydenham’s chorea
Patients with AIE may present with: movement disorders such as ataxia, dystonia, myoclonus, and orofacial dyskinesia.
Seizures are the most common symptom.
Autonomic disturbances including: diaphoresis, hypertension, tachycardia and hypoventilation are also frequent.
Some patients may develop gastrointestinal manifestations of diarrhea, gastroparesis, and constipation related to involvement of the myenteric plexus.
Sleep disturbances such as insomnia, abnormal sleep movements, sleep apnea, and hypersomnia may occur.
Autoimmune encephalitis is an immune response against neuronal antigens with production of antibodies.
Autoimmune encephalitis is linked to auto antibodies developed against intracellular or surface antigens.
Anti-neuronal antibodies are classified into antibodies: against cell surface antigens antibodies against synaptic antigens and antibodies against intraneuronal antigens
Diagnostic criteria for possible autoimmune encephalitis:
Subacute onset with rapid progression of less than three months of short-term memory loss, altered mental status, or psychiatric symptoms
New focal central nervous system findings
Seizures not explained by previously-known seizure disorder
Cerebrospinal fluid pleocytosis
Magnetic resonance imaging suggestive of encephalitis
Exclusion of alternative causes
Anti-N-methyl-D-aspartate receptor encephalitis is one of the most common causes of AIE.
ovarian teratomas are common.
It predominantly affects children and young female patients.
Underlying malignancies are found mainly in patients between 12–45 years; most of them are ovarian teratomas (94%), followed by extraovarian teratomas (2%), and other tumors (4%).
Herpes simplex virus-1 encephalitis is a trigger for anti-NMDAR encephalitis/
Most AIE cases after herpes zoster are now believed to be anti-NMDAR encephalitis.
Patients with anti-Α-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (anti-AMPAR) encephalitis usually present with seizures, memory impairment and psychosis.
anti-AMPAR) encephalitis patients may develop sleep disturbances and movement disorders.
Anti-AMPAR encephalitis has a paraneoplastic in etiology in 64% of cases: thymoma, ovarian teratoma and lung and breast cancer.
Brain MRI shows T2 and FLAIR hyperintensities, mainly in the medial temporal lobe.
Cerebrospinal fluid (CSF) examination may show pleocytosis and oligoclonal bands.
Anti-GABA-AR encephalitis is a rapidly progressive encephalopathy with early behavioral or cognitive changes that evolved with refractory seizures and multifocal lesions as seen on brain magnetic resonance imaging.
CSF analysis shows lymphocytic pleocytosis.
There is an underlying neoplasia in 27% of these patients, mostly thymomas, similar to that seen in patients with anti-gamma-aminobutyric acid B receptor and anti-AMPAR antibodies, they may also present with coexisting autoimmune disorders such as thyroiditis or myasthenia.
Anti-GABA-BR encephalitis is characterized by cognitive symptoms with severe seizures or status epilepticus, and other presentations include ataxia and opsoclonus-myoclonus.
About 50% were found to have small-cell lung cancer.
The long-term prognosis in anti-GABA-BR encephalitis is determined by the presence of an underlying malignancy.
Anti-LGI1 and anti-CASPR2 encephalitis, an anti-voltage-gated potassium channel-complex antibodies (anti-VGKC).
Other
Anti-GAD encephalitis
Anti-GlyR encephalitis
Anti-DPPX encephalitis
Anti-IgLON5 antibodies
Other autoimmune encephalitides:
IgLON5 antibodies
Anti-mGluR1 and anti-mGluR5 encephalitis
Anti-mGluR5-abs
Autoimmune encephalitis might occur without the identification of any pathogenic antibody, in which case it is called seronegative autoimmune encephalitis.
Therapeutic approach to autoimmune encephalitis is using as a first-line treatment corticosteroids and intravenous immunoglobulin.
Other options include the use of rituximab and tocilizumab or cyclophosphamide.