MRI cortical thickness in paediatric auto-immune encephalitis and acute disseminated encephalomyelitis

Objective: Paediatric autoimmune encephalitis and acute disseminated encephalomyelitis (ADEM) are neuroinflammatory disorders that can cause acute MRI abnormalities. Recent analyses suggest brain volume reductions months to years after disease onset. This study aimed to verify whether decreased gray matter thickness would also be observed in whole-brain cortical thickness as well as in temporal polar and orbitofrontal cortices.

Methods: A cohort of children previously diagnosed with autoimmune encephalitis (including anti- NMDA encephalitis and ADEM) were recruited at least two years after initial presentation and a cohort of typically developing children with no known neurological conditions. Cortical thickness across the whole-brain and in each region-of-interest was measured from T1w MRI scans using Freesurfer.

Results: MRI scans from 12 children with autoimmune encephalitis (mean age = 10.5; 8F:4M) and 48 controls (mean age = 10.7; 23F 25M) were analysed. The autoimmune encephalitis group had lower cortical thickness in a cluster covering the top part of the left superior occipital gyrus and the bottom part of the left superior parietal lobule (cluster size = 681.55 mm2; corrected cluster-wise p = 0.00459; clusterwise Cohen’s d= -8.3773). No multivariate effect on the cortical thickness of the regions-of-interest was found (Roy’s Largest Root = .095, F(df) = 1.207(4); p = .319; partial η2 = .087). A small univariate effect was observed, with autoimmune encephalitis predicting lower left orbitofrontal thickness (F = 4.407, p = .040, Partial η2 = .075).

Interpretation: Children with autoimmune encephalitis may be subject to local cortical thinning in the long term.