Autoimmune Encephalitis

Autoimmune encephalitis can manifest with several distinct syndromes. The classical presentation of encephalitis consists of a subacute (days to a few weeks) progressive decrease in the level of consciousness, often with fluctuations, and altered cognition. Memory maybe impaired early in the clinical course. Patients may progress to coma. While many cases of autoimmune encephalitis are indistinguishable from each other or viral encephalitis, there may be clues to specific autoimmune etiologies. It is typical for patients with autoimmuneencephalitis have testing for various infectious etiology. These disorders are strongly cancer associated and involve T-cell responses targeting neurons. The prognosis tends to be poor due to irreversible neuronal killing by these mechanisms. The antibodies in these disorders are usefultumor markers. Antibodies to cell surface antigens, such as the NMDA receptor is common. The associations with cancers are variable, and the prognosis tends to be much better. The serum and CSF titers of NMDA receptor antibodies have been measure. Serum titers didnot provide useful information on disease activity. CSF titers were generally higher in patients with acute illness or during relapse compared to patients in remission. Brain MRI in patients with NMDAR, AMPAR, LGI1, Caspr2,and GABA-B antibodies may be normal or showincreased T2 signal, especially in the medial temporal lobe.Brain MRI therefore does not distinguish between infectious and autoimmune causes, and a normal brain MRI does not exclude these causes PET or SPECT has shown diverse areas of regional hyper- or hypometabolismin patients with NMDAR, LGI1, Caspr2 or other autoantibodies Seizures may occur at any poi nt during the disease course of anti-NMDAR encephalitis, including at presentation. The extreme delta brush pattern may be observed in patients with anti-NMDAR encephalitis, most often in patients who are comatose. The status epilepticus in the setting of autoimmune encephalitis probably occurs more frequently withNMDAR antibodies overall LGI1 antibodies are associated with (FBD rapid jerking of one side of the face and/or upper extremity). Each seizure tends to be unilateral but they may occur on both sides. Brain biopsy generally is not used in the diagnosis of encephalitis forseveral reasons. Whenever a paraneoplastic disorder is suspected, tumor screening should be initiated promptl. When a particular autoimmune disease can be confirmed, this will clarify the risk of specific tumors and lead to more focused tumor screening. Most of the synaptic/ cell surface CNS autoantibodies can cause some form of limbic encephalitis, and these diseases can improve with immunotherapy. The criteria for definite autoimmune encephalitis require: (1) subacute symptoms, (2) brain MRI abnormalities localized to themedialtemporal lobes (3) EEG showing epileptic or slow-wave activity originating from the temporal lobes or pleocytosis onlumbar puncture, (4) exclusion of alterative causes.AMPA receptor antibodies target the GluR1 orGluR2 subunits of an ionotropic glutamate receptor widely expressed in the brain.The most common presentation is limbic encephalopathy, but other patients may have a diffuse encephalitis or present first with psychosis LGI1 antibodies are found mostly in older adults (median age of 60 years) and affect more men than women LGI1 antibodies areassociated with (FBD rapid jerking of one side of the face and/or upper extremity). Each seizure tends to be unilateral but they may occur on both sides. Treatment of the central nervous system synaptic and cell surface autoimmune disorder: IVIg is widely used as an initialtherapy, although its mechanisms in these disease are unclear. Plasma exchange rapidly reduces serum antibodies, but its effectiveness in decreasing CNS antibodies is unknown. Steroids are widely used at high doses initially. In the case of LGI1 antibodies, steroids may be particularly effective, and very slow tapers may be needed. Depletion of developing B cells with rituximab was initially considered a second-line therapy, but is increasingly being used early in the disease course with severely ill patients. Repeated courses of rituximab may be used in some patients, particularly those with relapses. Cyclophosphamide may be useful in patients who are critically ill or refractory to othertreatments, but carries risks of infertility and other toxicities. Gonadotropin-releasing hormone (GNRH) agonist treatment should be considered in young women receiving cyclophosphamide to decrease the risk of infertility.