Prion disease is a progressive, refractory, or lethal disease that occurs when normal prion disease present in the brain is converted into abnormal prion protein by some trigger, and the abnormal prion protein accumulates and damages neurons. Diagnosis of prion disease includes CSF examination, imaging examination, and electroencephalography. Of these three tests, the CSF test is the only cerebrospinal fluid testing center in Japan that has prion disease, and is conducting joint research with Europe, Asia, and the United States. We succeeded in amplifying and detecting a very small amount of abnormal prion protein present in cerebrospinal fluid in 2011. We are working every day to apply this technology to other neurodegenerative diseases. It has been successfully applied to some neurodegenerative diseases.