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Anti-NMDA receptor encephalitis is a severe autoimmune disease, first described in 2007.  Since then a number of cases have been published, suggesting that to date the disease is a considerably underdiagnosed entity. The clinical picture develops over a relatively long period of time and is initially characterised by psychiatric symptoms such as decreased levels of consciousness and hallucinations as well as paranoid behaviour. In the course of the disease neurological symptoms occur, in particular, seizures, autonomic dysfunction and dyskinesias. Due to the young age of many patients, the symptoms are often mistaken as to result from drug-induced psychosis. Anti-NMDA receptor Encephalitis was first described in young women with teratomas. In the past few years the disorder has also been reported in men and children and without any detectable neoplasia. The diagnosis is based on the characteristic clinical picture and supportive findings in MRI, EEG and the cerebrospinal fluid. Hereby, highly specific autoantibodies directed against the NR1 subunit of the NMDA-type glutamate receptors in the CSF (or serum) play an important role and should be sought specifically in any case of an "encephalitis of unknown cause". The prognosis of the disease is favourable, even when autonomic disorders entail ventilation and/or prolonged intensive care treatment is necessary. Nonetheless, the clinical outcome is highly dependent on an early diagnosis and immunotherapy without delay. In the case of a malignancy, tumour removal is also crucial. Taken together, an interdisciplinary approach including neurologists, psychiatrists, oncologists and gynaecologists is essential in order to detect and effectively treat this disorder., (© Georg Thieme Verlag KG Stuttgart · New York.)

Antibody-associated limbic encephalitis was usually seen as a paraneoplastic syndrome where the antibodies would target intracellular proteins. However, recent reports challenged this idea and described antibodies that target synaptic proteins expressed on the cell surface. These antibodies are not necessarily linked to tumors and should be regarded as a distinct entity of different autoimmune diseases. They are of direct clinical relevance since their binding to their target antigen is likely the cause of the clinical symptoms and, therefore, immune treatment often results in a beneficial outcome. Tests which differentiate these antibodies are now available in specialized laboratories.

In the past 10 years, the diagnosis and understanding of immune-mediated diseases of the gray matter of the CNS have greatly advanced with the discovery of autoantibodies in serum and CSF of affected patients. The newly described antibodies against neuronal surface antigens, i.e., receptors, channels, and associated proteins, seem to have a direct pathogenic effect on CNS neurons. Fortunately, there is a beneficial effect of immunotherapy in many patients. The diagnosis of autoantibody-associated disease of the CNS gray matter requires the combination of a typical clinical syndrome or a characteristic paraclinical finding (MRI, CSF, histopathology) with the detection of a specific antibody. In the following, an overview will first be given of the syndromes typically associated with autoantibodies. Thereafter, the diagnosis of these syndromes is discussed, and finally, preliminary treatment recommendations are given.

Anti-NMDA-receptor encephalitis is a severe and considerably underdiagnosed form of encephalitis with characteristic clinical features including psychiatric symptoms, decreased levels of consciousness, hypoventilation, epileptic seizures, autonomic dysfunction and dyskinesias. Most patients are primarily seen by psychiatrists, often on the assumption of a drug-induced psychosis. Anti-NMDA-receptor encephalitis had initially been described in young women with ovarian teratoma, but is also common in women without tumour, in men and in children. The diagnosis is based on the characteristic clinical picture, supporting findings of brain MRI, electroencephalogram and cerebrospinal fluid (CSF), and the presence of highly specific autoantibodies directed against the NR1 subunit of NMDA-type glutamate receptors in the serum or CSF. In particular, anti-NMDA-receptor encephalitis must be excluded in patients with 'encephalitis of unknown cause'. In principle, the prognosis is favourable and recovery from symptoms can be expected even after prolonged intensive care treatment and mechanical ventilation. However, improvement correlates with prompt identification of the disorder, early immunotherapy and - in the case of a malignancy - with complete tumour removal. Patient care requires an interdisciplinary approach including neurologists, psychiatrists, paediatricians, oncologists and gynaecologists.

Since the initial description of limbic encephalitis (LE) in 1960/1968, several subforms of this clinico-neuropathological syndrome have been identified. The best known is paraneoplastic LE. However, non-paraneoplastic forms have been reported, too. Very recently, autoantibodies against voltage-gated potassium channels have been described in association with LE. The diagnostic workup of such a case and the apparently typical good response to long-term immunotherapy of this LE subform are described.