Intervention: Patients presenting to the ED or the MUP or the NC with NTH are recruited during a 1-year-period. After informed consent is given by the patient, baseline data will be assessed including medical history, clinical items (i.e. neurological status, vital parameters, blood pressure, BMI) and routine laboratory items. Patients will be evaluated using a validated standardized diagnostic tool and questionnaire. CT scans and other diagnostics, such as lumbar puncture, MRI, etc., will be ordered upon request of the treating physician. All diagnostic procedures, results, diagnosis made by the treating physicians and initiated therapy will be recorded. Copeptin will be measured on admission by batch analysis by blinded laboratory staff upon completion of the study.