Autoimmune Encephalitis Resembling Dementia Syndromes.

Area of Science:

• Neurology
• Immunology
• Neuroscience

Background:

• Autoimmune encephalitis (AIE) can present with symptoms overlapping neurodegenerative dementia syndromes.
• Patients with AIE do not always exhibit classic encephalitis symptoms, leading to diagnostic challenges.

Purpose of the Study:

• To evaluate the frequency of AIE mimicking dementia in middle-aged and older patients.
• To identify red flags for AIE in this demographic to improve early diagnosis.

Main Methods:

• Nationwide observational cohort study.
• Included patients (age ≥45 years) with anti-LGI1, anti-NMDAR, anti-GABA_BR, or anti-CASPR2 encephalitis meeting dementia criteria and lacking early prominent seizures.
• Analyzed clinical presentation, diagnostic findings, and treatment outcomes.

Main Results:

• 38% of 175 older AIE patients (≥45 years) met dementia criteria without early seizures.
• Rapid cognitive decline (76%) and subtle seizures (27%) were observed; 25% lacked typical inflammatory brain MRI or CSF findings.
• Abnormal CSF biomarkers, including 14-3-3, were frequent (61% tested).

Conclusions:

• Key red flags for AIE in suspected dementia cases include rapidly progressive cognitive decline, subtle seizures, and atypical ancillary test results.
• Physicians must consider AIE even without typical inflammatory signs, as biomarkers for dementia can be abnormal.
• Prompt diagnosis and immunotherapy significantly benefit most AIE patients.