# Abnormal Magnetic Resonance Imaging Patterns in Patients with Neuropsychiatric Disorders Due to Anti-NMDA Receptor Encephalitis: A Comparative Study

## TL;DR

This study shows that MRI patterns in anti-NMDA receptor encephalitis help distinguish it from other conditions, but overlap with some autoimmune disorders.

## Contribution

The study identifies specific MRI patterns in ANMDARE and compares them with other neuropsychiatric disorders.

## Key findings

- T2-FLAIR MRI abnormalities are common in medial temporal, paralimbic, and posterior neocortical regions in ANMDARE.
- Pachymeningeal enhancement was observed in 26.1% of ANMDARE patients.
- MRI findings differentiate ANMDARE from primary psychotic disorders but overlap with antibody-negative autoimmune encephalitis.

## Abstract

Background: Brain MRI abnormalities in anti-NMDA receptor encephalitis (ANMDARE) are classically described in limbic structures, particularly the medial temporal lobe. Paralimbic, neocortical, and meningeal abnormalities have been less consistently reported. Objective: The objective was to evaluate the diagnostic value of brain MRI abnormalities in patients with definite ANMDARE. Methods: We conducted a case–control study including 115 patients with ANMDARE and 115 controls with primary psychotic disorders or antibody-negative autoimmune encephalitis. Structural MRI studies were systematically reviewed by an expert neuroradiologist blinded to clinical diagnosis. Results: ANMDARE patients were younger and more frequently presented with seizures, dyskinesia, severe neuropsychiatric disturbances, abnormal cerebrospinal fluid and EEG findings, and worse outcomes, including mortality. T2-T2-FLAIR abnormalities commonly involved medial temporal limbic structures, paralimbic regions (anterior cingulate and insular cortices), and neocortical areas (parieto-occipital cortices). Pachymeningeal enhancement was observed in 26.1% of patients. MRI findings clearly differentiated ANMDARE from primary psychotic disorders but largely overlapped with antibody-negative autoimmune encephalitis, except for limited parietal and occipital differences. Conclusions: T2-FLAIR MRI abnormalities involving medial temporal, paralimbic, and posterior neocortical regions are common in ANMDARE. Pachymeningeal enhancement is not rare. While useful for distinguishing ANMDARE from primary psychotic disorders, a substantial overlap with antibody-negative autoimmune encephalitis was observed.