A neurodegenerative disease or condition is diagnosed in a subject by obtaining a sample of cerebral spinal fluid from the subject and assaying the sample by an assay method that detects the presence of at least one antiphospholipid autoantibody in the sample, wherein an elevated level of at least one antiphospholipid autoantibody in the sample of cerebral spinal fluid correlates with a neurodegenerative disease or condition in the subject. The neurodegenerative disease or condition may also be diagnosed by assaying a sample of cerebral spinal fluid to detect nitrosylated antibodies, wherein an elevated level of nitrosylated antibodies correlates with a neurodegenerative disease or condition in said subject. A neurodegenerative disease or condition is also detected or diagnosed by assaying a first sample of cerebral spinal fluid from the subject to determine a level of at least one autoantibody having a selected specificity, treating a second sample of cerebral spinal fluid with an oxidizing agent and assaying the oxidized second sample to determine a level the at least autoantibody having the selected specificity, and comparing the level of the at least one autoantibody in the first sample with the level of the at least one autoantibody in the oxidized second sample, wherein a lack of increase in the level of the at least one autoantibody in the oxidized second sample as compared to the level of the at least one autoantibody in the first sample correlates with a neurodegenerative disease or condition in said subject.
