The present invention provides methods for diagnosing neurodegenerative disease, such as Alzheimer's Disease, Parkinson's Disease, and dementia with Lewy body disease by detecting a pattern of gene product expression in a cerebrospinal fluid sample and comparing the pattern of gene product expression from the sample to a library of gene product expression pattern known to be indicative of the presence or absence of a neurodegenerative disease. The methods also provide for monitoring neurodegenerative disease progression and assessing the effects of therapeutic treatment. Also provided are kits, systems and devices for practicing the subject methods.