Background/Purpose: Anti-NMDAR encephalitis may be more prevalent than some forms of viral encephalitis in children. Pediatric rheumatologists are called upon to assist in the diagnosis and immuno-modulation of children with autoimmune encephalitides (AE). With prompt identification and early B cell depletion clinical outcomes may be robust in these disorders. Yet, children younger than 5 years of age with anti-NMDAR encephalitis may present differently than older patients and pose a diagnostic challenge. We present the presentation and outcomes of a  cohort of young NMDAR encephalitis patients treated at a single center using a standardized step-up approach.

Methods:

• After obtaining approval from a local IRB we reviewed the charts of children diagnosed with Anti-NMDAR encephalitis between Jan 2012-April 2019 at a pediatric tertiary hospital. Diagnosis was based on clinical findings, and serum and CSF-Anti-NMDAR IgG antibodies. We reviewed all treatment modalities, adverse events of immunosuppression, and assessed disability at hospital discharge and last follow up using the Modified Rankin Scale (mRS) for children. 

Results: Nine (20%) of children diagnosed with NMDAR encephalitis were < 5 years of age at presentation (Median age 3 years, range 1.5-5 yr; , 67% F).  Presentations in younger children included gait disturbances, encephalopathy, reduction in speech, acute regression and severe movement disorders. Unlike older patients, seizures occurred in only one child. Median time to AE diagnosis was 5 days (range 4-99 days). Treatment followed a standardized institution protocol of: methylprednisolone, IVIG, and rituximab (2 doses at 500 mg/m2). Rituximab was administered 5-7 days after IVIG if a child did not show significant improvement. Children received rituximab at a median of 33 d, (range 16-128 d) from symptom onset. All children tolerated rituximab without infections or adverse events. All children with > 6 month follow-up re-populated their B cells, and none flared.

Prolonged hospitalizations were prevalent (median LOS 30 d, range 7-100 d) Five (55%) children required inpatient rehabilitation after initial hospital discharge. Modified Rankin Scale (mRS) scores improved from 4-5 (moderately severe-severe) at presentation to a mRS of 1 (mild symptoms) in one child (11%), a 2 (slight disability) in 5 children (56%), and a 3 in three children (33%) at their last visit (median f/u time 310 days, range 34-1219 d). Disability scores for younger children were higher than those of older patients (whose scores were predominantly 0-1). Deficits at time of last follow up related to language skills, and behavioral concerns.

Conclusion: Younger children with NMDAR encephalitis present differently than the “classic” phenotype of older children. Early B cell depletion practices were well tolerated in younger children. With rehabilitation, there were gradual and sustained gains in function in all children. It is unclear if greater disability of younger children was related to a shorter follow-up period or is a reflection of the vulnerability of toddlers to acquired CNS insults. There is a need for pediatric centers to share AE data so to answer questions regarding appropriate therapy and functional outcomes.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/is-early-standardized-rituximab-therapy-sufficient-for-toddlers-with-nmdar-encephalitis/