Long-Term Outcomes in Antibody-Negative Autoimmune Encephalitis: A Retrospective Study

Area of Science:

• Neuroimmunology
• Neurology

Background:

• Antibody-negative autoimmune encephalitis (AE) constitutes a significant portion of AE cases but remains understudied.
• Cases lacking typical AE-defining features are particularly underrepresented in research.

Purpose of the Study:

• To characterize the long-term outcomes of patients diagnosed with "possible only" or "probable" autoimmune encephalitis (AE).
• To evaluate the efficacy of immunotherapy and identify predictors of long-term prognosis in antibody-negative AE.

Main Methods:

• Retrospective analysis of adult patients with "possible only" or "probable but antibody-negative" AE from 2006-2020.
• Inclusion criteria required at least one year of follow-up; all patients underwent neural antibody testing.
• Data collected included baseline disability (modified Rankin Scale [mRS]), CSF and MRI findings, time to immunotherapy, and clinical outcomes.

Main Results:

• Forty-five patients were included, with a median follow-up of 36 months. Most presented with significant disability (mRS ≥3) at baseline.
• Immunotherapy led to at least partial improvement in 98% of treated patients, though 31% experienced relapses.
• Common long-term symptoms included memory dysfunction (69%) and attention deficits (38%). Most achieved independence (median mRS 2), but 11 had poor outcomes (mRS ≥3).

Conclusions:

• Patients with clinically presumed antibody-negative AE can achieve significant improvement with immunotherapy, underscoring the importance of early intervention.
• Early functional status (mRS) and the need for gait assistance at three months post-onset are predictive of long-term neurological outcomes.