Immunotherapy-responsive dementias and encephalopathies.

The diagnosis of an autoimmune dementia requires the detection of objective improvements in cognitive decline (usually subacute in onset with a fluctuating course) after a course of immunotherapy. Serum and CSF antibody markers of autoimmunity (particularly those with neural antigen specificity) as well as other CSF markers of inflammation increase the suspicion for an autoimmune cause. The detection of neural autoantibodies should raise concern for a paraneoplastic etiology and may inform a targeted oncologic evaluation (eg, NMDA receptor antibodies are associated with teratoma). MRI, EEG, functional imaging, and neuropsychological evaluations provide objective evidence of neurologic dysfunction by which the success of immunotherapy may be measured. Most treatment information emanates from retrospective case series and expert opinion. Nonetheless, early intervention allows reversal of deficits in many patients. Chronic treatment is often required to maintain remission.