An in vitro method for the detection, determination of severity and monitoring and prognosis of neurodegenerative diseases is disclosed. The presence and/or concentration of the physiologically inactive proadrenomedullin (proADM) partial peptide, in particular, the midregional proADM partial peptide, is determined in a biological fluid of a patient who is suffering from a neurodegenerative disease or is suspected of having such a disease. Conclusions about the presence, course, severity or success of a treatment of the neurodegenerative disease are drawn on the basis of the presence and/or concentration of the specific partial peptide in the biological sample.