Long-Term Cognitive Outcome in Anti-N-Methyl-D-Aspartate Receptor Encephalitis.

OBJECTIVE: Cognitive dysfunction is a core symptom of anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis, but detailed studies on prevalence, characteristics of cognitive deficits, and the potential for recovery are missing. Here, we performed a prospective longitudinal study to assess cognitive long-term outcome and identify clinical predictors. METHODS: Standardized comprehensive neuropsychological assessments were performed in 43 patients with NMDAR encephalitis 2.3 years and 4.9 years (median) after disease onset. Cognitive assessments covered executive function, working memory, verbal/visual episodic memory, attention, subjective complaints, and depression and anxiety levels. Cognitive performance of patients was compared to that of 30 healthy participants matched for age, sex, and education. RESULTS: All patients had persistent cognitive deficits 2.3 years after onset, with moderate or severe impairment in >80% of patients. Core deficits included memory and executive function. After 4.9 years, significant improvement of cognitive function was observed, but moderate to severe deficits persisted in two thirds of patients, despite favorable functional neurological outcomes (median modified Rankin Scale = 1). Delayed treatment, higher disease severity, and longer duration of the acute phase were predictors for impaired cognitive outcome. The recovery process was time dependent, with greater gains earlier after the acute phase, although improvements were possible for several years after disease onset. INTERPRETATION: Cognitive deficits are the main contributor to long-term morbidity in NMDAR encephalitis and persist beyond functional neurological recovery. Nonetheless, cognitive improvement is possible for several years after the acute phase and should be supported by continued cognitive rehabilitation. Cognition should be included as an outcome measure in future clinical studies. ANN NEUROL 2021;90:949-961.

Hippocampal hub failure is linked to long-term memory impairment in anti-NMDA-receptor encephalitis: insights from structural connectome graph theoretical network analysis.

BACKGROUND: Anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis is characterized by distinct structural and functional brain alterations, predominantly affecting the medial temporal lobes and the hippocampus. Structural connectome analysis with graph-based investigations of network properties allows for an in-depth characterization of global and local network changes and their relationship with clinical deficits in NMDAR encephalitis. METHODS: Structural networks from 61 NMDAR encephalitis patients in the post-acute stage (median time from acute hospital discharge: 18 months) and 61 age- and sex-matched healthy controls (HC) were analyzed using diffusion-weighted imaging (DWI)-based probabilistic anatomically constrained tractography and volumetry of a selection of subcortical and white matter brain volumes was performed. We calculated global, modular, and nodal graph measures with special focus on default-mode network, medial temporal lobe, and hippocampus. Pathologically altered metrics were investigated regarding their potential association with clinical course, disease severity, and cognitive outcome. RESULTS: Patients with NMDAR encephalitis showed regular global graph metrics, but bilateral reductions of hippocampal node strength (left: p = 0.049; right: p = 0.013) and increased node strength of right precuneus (p = 0.013) compared to HC. Betweenness centrality was decreased for left-sided entorhinal cortex (p = 0.042) and left caudal middle frontal gyrus (p = 0.037). Correlation analyses showed a significant association between reduced left hippocampal node strength and verbal long-term memory impairment (p = 0.021). We found decreased left (p = 0.013) and right (p = 0.001) hippocampal volumes that were associated with hippocampal node strength (left p = 0.009; right p < 0.001). CONCLUSIONS: Focal network property changes of the medial temporal lobes indicate hippocampal hub failure that is associated with memory impairment in NMDAR encephalitis at the post-acute stage, while global structural network properties remain unaltered. Graph theory analysis provides new pathophysiological insight into structural network changes and their association with persistent cognitive deficits in NMDAR encephalitis.

Normal gut microbiome in NMDA receptor encephalitis.

OBJECTIVE: To determine whether the gut microbiota shows overabundance of commensal bacteria species in patients with anti-NMDA receptor (NMDAR) encephalitis, similar to patients with MS or neuromyelitis optica where they potentially balance pro- and anti-inflammatory immune responses or participate in disease pathogenesis by molecular mimicry. METHODS: Intestinal microbiota was characterized in patients with NMDAR encephalitis (n = 23, mean age: 34 ± 12.7 years; 21 females) and age/sex/environment-matched healthy controls (n = 24, 40 ± 14.2 years; 22 females) using stool bacteria 16S rDNA sequencing and classification in operational taxonomic units (OTUs). Statistical analyses focused on intraindividual and interindividual bacterial diversity and identification of differentially abundant taxa. RESULTS: Patients with NMDAR encephalitis and controls had similar microbiome profiles of the gut microbiota regarding intraindividual bacterial diversity, OTU distribution, ratio between regional and local species diversity when testing all OTUs, and genera with a relative abundance greater than 0.5%. Similarly, the subgroup of NMDAR encephalitis patients with an ovarian teratoma (n = 3) showed no differences in microbiome variation compared with controls. Patients in the acute encephalitis stage (n = 8) showed significant differences in the numbers of Clostridium XVIII, Clostridium IV, Oscillibacter, Prevotella, and Blautia; however, significance was lost after correction for multiple testing. CONCLUSION: Patients with NMDAR encephalitis and controls both had a normal gut microbiome. The lack of overabundance of certain bacterial species in patients suggests that microbiome changes are no major contributors to the pathogenesis, disease course, or prognosis in NMDAR encephalitis. Despite the small sample size and heterogeneous groups, findings indicate differences to other neuroimmunologic diseases.