A neurodegenerative disease or condition is diagnosed by obtaining a sample of cerebral spinal fluid and assaying the sample to detect the presence of at least one antiphospholipid autoantibody or nitrosylated antibodies in the sample, an elevated level of which correlates with a neurodegenerative disease or condition. Alternatively, by assaying a first sample to determine a level of at least one autoantibody having a selected specificity, treating a second sample with an oxidizing agent, assaying the oxidized second sample to determine a level of the at least autoantibody having the selected specificity, and comparing the level of the at least one autoantibody in the first sample with that in the oxidized second sample, a lack of increase in the level of the at least one autoantibody in the oxidized second sample as compared to the level in the first sample correlates with a neurodegenerative disease or condition.
