**5. Conclusion**

The discovery of autoantibodies in different CNS diseases can support an early diagnosis and treatment monitoring. Moreover, antibodies can contribute to a better understanding of the disease pathogenesis. However, an antibody seronegative result should be handled with care, as this can be linked to the assay methodology, study population or to therapeutic intervention. In contrast to the high sensitivity and specificity of anti-AQP4 autoantibodies in NMO patients, antibodies to MOG are discovered "only" in a subgroup of ADEM patients. Hence, there is a lack of a specific biomarker for more than half of patients diagnosed with ADEM. Future studies focusing on these seronegative patients might facilitate a reclassification of CNS diseases through the identification of novel biomarkers. Finally, antibodies to NMDA-R are highly specific for NMDA-receptor encephalitis, whereas their role in other neurological diseases has to be confirmed by specific assays.
