Cognitive outcomes following anti-N-methyl-D-aspartate receptor encephalitis: A systematic review

Abstract

Introduction: Anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis is an immune-mediated neurological disorder that (among other severe neuropsychiatric symptoms) affects cognition. This study aimed to summarize current knowledge regarding the rates, nature, and predictors of neuropsychological dysfunction in patients recovering from anti-NMDAR encephalitis.

Method: A systematic review of studies describing neuropsychological outcomes following anti-NMDAR encephalitis was conducted. Electronic databases Medline, PsycINFO, EMBASE, and CINAHL were searched from inception to September 2016. Results were summarized using descriptive statistics and a series of chi-square analyses.

Results: Of 4030 identified studies, 44 were included. These reported neuropsychological outcomes for 109 treated patients (83.5% female, M_age = 22.5 years, range = 2-67) recovering from anti-NMDAR encephalitis. High rates of neuropsychological dysfunction were identified, with diverse impairments of variable severity documented in >75% of patients at assessments conducted during acute, subacute, and longer term recovery periods. Despite this, cognitive outcomes were ultimately considered favorable in most cases (74.3%). This estimate does not account for the potential impact of relapses. The frequency of impairments in overall intellectual functioning, language, attention, working memory, and visuospatial functions were significantly higher within the acute recovery period than in later phases of convalescence. However, rates of impaired processing speed, episodic memory, and aspects of executive functioning were consistent across time points. Adverse neuropsychological outcomes occurred at significantly higher frequency in patients where immunotherapy was delayed, χ²(1, N = 66) = 10.84, p < .003.

Conclusions: Neuropsychological deficits are prevalent at all points of recovery from anti-NMDAR encephalitis, although improvement in cognitive outcomes can be expected as patients recover. Some cognitive deficits may be less likely than others to resolve. Close neuropsychological monitoring is warranted in this population. Longitudinal studies of neuropsychological functioning of patients with anti-NMDAR encephalitis are needed to accurately inform prognosis.

Keywords: Anti-N-methyl-D-aspartate receptor encephalitis; autoimmune diseases; cognitive disorders; neuropsychological tests; treatment outcome.