Screening 1021 Swedish memory clinic visitors for autoantibody-mediated encephalitis

Area of Science:

• Neurology
• Immunology
• Neuroscience

Background:

• Autoimmune encephalitis (AE) is a treatable condition that can mimic neurodegenerative dementia.
• Regional variations in AE prevalence in Sweden suggest potential underdiagnosis.
• This study investigated the presence of undetected AE in patients attending memory clinics.

Purpose of the Study:

• To determine the prevalence of AE autoantibodies in patients visiting memory clinics.
• To evaluate the utility of AE autoantibody testing in this patient population.
• To explore potential diagnostic tools for identifying AE in memory impairment cases.

Main Methods:

• Retrospective screening of 1021 individuals at memory clinics for AE autoantibodies (CASPR2, GABA_BR, IgLON5, LGI1, NMDA-R) using live cell-based assays.
• Positive samples were further tested with fixed cell-based assays and tissue-based assays.
• Clinical information and diagnostic tools like the STAM3mP score were used to assess antibody relevance.

Main Results:

• Eleven patients tested antibody-positive; three had phenotypes suggestive of AE.
• Antibodies to CASPR2 or NMDA-R were found in patients with CSF-specific IgG bands or increased Kappa free light-chain.
• Six of seven previously undiagnosed antibody-positive patients scored positively on the STAM3mP score, indicating potential treatment response.

Conclusions:

• AE is a rare differential diagnosis in memory clinic attendees.
• Unselective AE autoantibody testing is not suitable for memory clinics due to low prevalence.
• Rigorous clinical evaluation, potentially aided by tools like the STAM3mP score, is recommended for identifying potential AE cases, warranting further research into pre-screening biomarkers.