Clinical characteristics, treatments, outcome, and prognostic factors of severe autoimmune encephalitis in the intensive care unit: Standard treatment and the value of additional plasma cell-depleting escalation therapies for treatment-refractory patients

Background and purpose: To investigate severe autoimmune encephalitis (AE) in the intensive care unit (ICU) with regard to standard treatment in responsive patients and additional escalation therapies for treatment-refractory cases.

Methods: This retrospective, single-center study analyzed medical records of ICU-dependent AE patients for clinical characteristics, treatments, prognostic factors, and neurological outcome as quantified by modified Rankin Scale (mRS) and Clinical Assessment Scale for Autoimmune Encephalitis (CASE).

Results: From 40 enrolled patients (median age = 52 years; range = 16-89 years) with AE mediated by neuronal surface antibodies (nsAb; 90%) and AE with onconeuronal antibodies (10%), 98% received first-line therapy. Of those, 62% obtained additional second-line therapy, and 33% received escalation therapy with bortezomib and/or daratumumab. Good neurological outcome, defined as mRS = 0-2, was observed in 47% of AE with nsAb (CASE = 5), 77% of anti-N-methyl D-aspartate receptor encephalitis patients (CASE = 1), whereas AE patients with onconeuronal antibodies had the poorest outcome (mRS = 6, 100%). Treatment-refractory AE patients with nsAb requiring escalation therapy achieved similarly good recovery (mRS = 0-2, 39%, CASE = 3) as patients improving without (mRS = 0-2, 54%, CASE = 4), although they presented a higher disease severity at disease maximum (mRS = 5 100% versus 68%, CASE = 24 versus 17; p = 0.0036), had longer ICU stays (97 versus 23 days; p = 0.0002), and a higher survival propability during follow-up (p = 0.0203). Prognostic factors for good recovery were younger age (p = 0.025) and lack of preexisting comorbidities (p = 0.011).

Conclusions: Our findings suggest that treatment-refractory AE patients with nsAb in the ICU can reach similarly good outcomes after plasma cell-depleting escalation therapy as patients already responding to standard first- and/or second-line therapies.