Abstracts

Rationale: Anti-N-methyl-D-aspartate receptor (anti-NMDAR) encephalitis is a multistage illness that progresses from psychosis, seizures, memory deficits, and language disintegration into a state of unresponsiveness with catatonic features, often associated with abnormal movements, autonomic and breathing instability. Despite the severity of the disorder, most patients respond well to immunotherapy and tumor removal in paraneoplastic cases. The correlations between these symptoms and the connectivity patterns of the default mode (DMN) using resting state (RS) functional magnetic resonance imaging (fMRI) are still unknown. The objective of this study is to describe DMN connectivity alterations in patients with anti-NMDAR encephalitis. Methods: We acquired RS fMRI in three patients with anti-NMDAR encephalitis: one previous to treatment, and two patients after several courses of immunotherapy and complete remission of symptoms (one patient after 54 months and the other after 10 months of treatment). All patients had seizures and psychiatric symptoms in the acute phase. fMRIs and structural images (SI) were acquired in a 3T MRI. We preprocessed and analyzed images with the UFC toolbox: fMRIs realignment, normalization (MNI-152) and smoothing, SI tissue segmentation and normalization. We regressed the fMRIs for head motion, white matter and cerebral spinal fluid global signals and band-pass filtered (0.008-0.1 Hz). We used 18 ROIs (regions of interest) of the DMN to perform individual cross-correlation analysis. Sequentially, the individuals' adjacency matrices were taken to the second level analysis: results from each patient were compared separately to a control group of 26 subjects with similar age range, using Z-test, evaluating if any of the tested connections was significantly distinct from controls (p < 0.05 FDR corrected for multiple ROI-wise comparisons). Results: The two asymptomatic treated patients had no differences in connectivity patterns compared to controls. However, the patient who had RS fMRI before treatment showed an abnormal inverse pattern of connectivity between mid-cingulum and thalami (figure 1). Conclusions: This preliminary finding suggests that an aberrant pattern of activation between cingulum and subcortical structures may occur in patients with anti-NMDAR encephalitis, which may return to normal basal pattern after successful treatment. Further longitudinal studies are necessary to confirm this finding. Funding: São Paulo Research Foundation (FAPESP)