[Autoimmune encephalitis with psychotic symptoms : Diagnostics, warning signs and practical approach]

Despite intensive research, a precise cause of schizophrenic and schizoaffective disorders has not yet been identified. Therefore, psychiatric diagnoses are still made based on clinical ICD-10/DSM‑5 criteria and not on any objective markers; however, various causes or pathophysiological processes may ultimately lead to similar symptoms. An important task for the future of psychiatry is to identify disease subtypes with a distinct pathophysiology to develop more specific and causally acting therapies. A new diagnostic entity has become established in clinical neurology and psychiatry in recent years: autoimmune encephalitis with psychotic symptoms caused by specific antineuronal antibodies has been identified as a rare but potentially treatable cause of psychotic disorders; however, these inflammatory brain diseases are not reliably detected by routine psychiatric diagnostics. Therefore, this qualitative review is intended to provide structured support for clinical practice, which, guided by clinical warning signals, enables a rapid and reliable diagnosis as well as the initiation of immunotherapy. In the case of psychiatric symptoms, the additional onset of focal neurological signs, disturbances of consciousness and orientation, autonomic instability or epileptic seizures and electroencephalograph (EEG) abnormalities should always be followed by a more specific cerebrospinal fluid analysis with determination of antineuronal autoantibodies. Although the scientific evidence indicates that only a small subgroup of patients is affected, the swift and correct diagnosis is of high therapeutic and prognostic relevance for the affected individuals.

Antikörper-Diagnostik bei Verdacht auf autoimmune Hirnentzündungen

Der Nachweis spezifischer gegen Hirngewebe gerichteter Autoantikörper hat zu einer rasanten Weiterentwicklung in der Neurologie und Pädiatrie geführt. Mit ihrer Hilfe können heute bestimmte Symptome zweifelsfrei zugeordnet werden, diagnostische Pfade werden vereinfacht und immunmodulierende Therapien können gezielter eingesetzt werden. Die Krankheitsbilder reichen von Enzephalitiden und Epilepsien bis zu demyelinisierenden Erkrankungen, Psychosen und Demenzen. Angesichts der vielen neuen zugrundeliegenden Autoantikörper gegen Ionen -kanäle und Rezeptoren auf Nervenzellen (zum Beispiel NMDA-, AMPA- und GABA Rezeptoren, LGI1, DPPX) wächst die Schwierigkeit, den Überblick über das variable Erkrankungsspektrum zu behalten. Neben klinischer Untersuchung und MRT-Bild -gebung stehen die Lumbalpunktion und die Bestimmung der Antikörper mit zellbasierten Testverfahren im Vordergrund differenzial -dia gnostischer Entscheidungen und rascher Therapie. Der Nachweis immer neuer Antikörper wird sich in den kommenden Jahren fort-setzen und zu einem besseren Verständnis der Pathomechanismen auch einiger neurologischer Krankheiten führen, die bisher als unheilbar oder psychosomatisch galten.

[Pathophysiology and Prognostic Factors of Autoimmune Encephalitis]

More and more forms of autoimmune encephalitis are being identified with the clinical spectrum ranging from epilepsy over movement disorders to psychosis. The increasing appreciation of clinical symptoms raises questions about the underlying pathophysiological mechanisms and prognostic factors. Numerous novel findings on the aetiology demonstrate that diverse tumours, but also infections of the central nervous system such as Herpes encephalitis can trigger autoimmune encephalitis. Antibodies against neuronal surface epitopes are directly pathogenic in the majority of cases. They act via binding and internalization of target proteins, receptor blockage, or activation of complement. Most relevant for the patients' prognosis are the type and titer of antibodies (e. g. against NMDA, GABA, AMPA receptors or voltage-gated potassium channel complexes), associated tumours, sufficiently aggressive immunotherapies, and imaging as well as cerebrospinal fluid biomarkers.