Anti-N-methyl-D-aspartate receptor encephalitis (ANMDARE) is a rare and progressive neurological autoimmune disease that disproportionally affects pediatric patients (Yeshokumar et al., 2022). Patients diagnosed with ANMDARE experience a host of neurocognitive and psychiatric sequelae, but data on the rate of recovery are generally mixed (Wilkinson-Smith et al., 2022). Misdiagnosis of ANMDARE is common and may complicate recovery given the progressive nature of the syndrome (Shimoyama et al., 2016); thus, knowledge of the etiology may result in enhanced resolution of symptoms. The current study assessed the rate of functional recovery for pediatric patients diagnosed with ANMDARE and admitted to an inpatient rehabilitation program. Specifically, we hypothesized that patients with idiopathic autoimmune encephalitis (IAE) would have a protracted rate of acute recovery compared to patients diagnosed with ANMDARE.

The current study included archival data of pediatric patients (N=10) aged 3-16 years (M=12.39, SD=4.97) admitted to an inpatient rehabilitation program at a metropolitan academic medical center between 2017-2022; of these patients, 7 were characterized as having IAE, 5 were female-at-birth, and 7 were of Hispanic/Latine origin. The Functional Independence Measure for Children (WeeFIM; Msall et al., 1994) domain scores (i.e., cognition, self-care, mobility, motor) were utilized to assess acute recovery. Welch’s t-tests were analyzed separately at admission and discharge between etiological conditions (i.e., idiopathic vs. known) for each WeeFIM domain. Subsequently, change scores were calculated across the length of inpatient stay for each WeeFIM domain, and Welch’s t-tests determined statistical differences in change scores between etiological conditions.

Contrary to predictions, WeeFIM self-care domain scores were significantly higher at inpatient admission for patients with IAE (M=27.57) as compared to patients with ANMDARE (M=13.00), t(7) = 1.95, p < .05; trending differences were also found in admission scores on the WeeFIM motor domain between IAE (M=43.86) and ANMDARE (M=24.00) diagnostic groups, t(6) = 1.71, p = .07. Consistent with predictions, patients with ANMDARE generally had an appreciable acute recovery as compared to patients with IAE. Specifically, trending differences were found in change scores on the WeeFIM self-care domain between IAE (M=10.29) and ANMDARE (M=30.33) diagnostic groups, t(6) = -1.64, p = .05. Likewise, trending differences were found in change scores on the WeeFIM motor domain between IAE (M=21.43) and ANMDARE (M=47.67) diagnostic groups, t(5) = -1.82, p = .06. No significant or trending differences were observed at discharge.

Results have implications for optimizing the assessment and treatment of pediatric patients diagnosed with autoimmune encephalitis. Specifically, patients with ANMDARE may have a more severe initial presentation yet improved recovery course compared to patients characterized as idiopathic during their inpatient stay, particularly in motor and self-care functional domains; data highlights the importance of inpatient rehabilitation for patients diagnosed with ANMDARE. Current limitations include small sample sizes across diagnostic groups, likely due to the rarity of the disease. It is recommended that future research investigate the prognosis of pediatric patients diagnosed with autoimmune encephalitis longitudinally, at follow-up and across the lifespan.