MR Imaging Findings in Anti-Leucine-Rich Glioma Inactivated Protein 1 Encephalitis: A Systematic Review and Meta-analysis
Francisco Almeida, Ana I. Pereira, Catarina Mendes-Pinto, Joana Lopes, João Moura, José Maria Sousa, Gonçalo Videira, Raquel Samões, Tiago Gil Oliveira
Abstract
<h3>BACKGROUND:</h3> Antibodies against leucine-rich glioma inactivated protein 1 (LGI1) constitute a common form of autoimmune encephalitis. On MR imaging, it may show T2 FLAIR hyperintensities of the medial temporal lobe (T2 FLAIR-MTL), involve the basal ganglia, or be unremarkable. <h3>PURPOSE:</h3> We performed a systematic review and meta-analysis to obtain prevalence estimates of abnormal findings on MR imaging in anti-LGI1 encephalitis. A human brain map of the <i>LGI1</i> microarray gene expression was derived from the Allen Human Brain Atlas. <h3>DATA SOURCES:</h3> PubMed and Web of Science were searched with the terms “LGI1” and “encephalitis” from inception to April 7, 2022. <h3>STUDY SELECTION:</h3> Thirty-one research publications, encompassing case series and retrospective cohort and case-control studies, with >10 patients with anti-LGI1 encephalitis and MR imaging data were included. <h3>DATA ANALYSIS:</h3> Pooled prevalence estimates were calculated using Freeman-Tukey double-arcsine transformation. Meta-analysis used DerSimonian and Laird random effects models. <h3>DATA SYNTHESIS:</h3> Of 1318 patients in 30 studies, T2 FLAIR-MTL hyperintensities were present in 54% (95% CI, 0.48–0.60; I<sup>2</sup> = 76%). Of 394 patients in 13 studies, 27% showed bilateral (95% CI, 0.19–0.36; I<sup>2</sup> = 71%) and 24% unilateral T2 FLAIR-MTL abnormalities (95% CI, 0.17–0.32; I<sup>2</sup> = 61%). Of 612 patients in 15 studies, basal ganglia abnormalities were present in 10% (95% CI, 0.06–0.15; I<sup>2</sup> = 67%). <i>LGI1</i> expression was highest in the amygdala, hippocampus, and caudate nucleus. <h3>LIMITATIONS:</h3> Only part of the spectrum of MR imaging abnormalities in anti-LGI1 encephalitis could be included in a meta-analysis. MR imaging findings were not the main outcomes in most studies, limiting available information. I<sup>2</sup> values ranged from 62% to 76%, representing moderate-to-large heterogeneity. <h3>CONCLUSIONS:</h3> T2 FLAIR-MTL hyperintensities were present in around one-half of patients with anti-LGI1. The prevalence of unilateral and bilateral presentations was similar, suggesting unilaterality should raise the suspicion of this disease in the appropriate clinical context. Around 10% of patients showed basal ganglia abnormalities, indicating that special attention should be given to this region. <i>LGI1</i> regional expression coincided with the most frequently reported abnormal findings on MR imaging. Regional specificity might be partially determined by expression levels of the target protein.