GAD2 and stiff-person syndrome: Recent research has concluded that high anti-GAD65 antibody levels in the serum (titers > 20 nmol/L) or CSF are associated with various autoimmune neurological diseases, including autoimmune epilepsy, SPS, cerebellar ataxia, limbic encephalitis, progressive encephalomyelitis with rigidity and myoclonus, and PNS [10].