Claustrum hyperintensity as a marker of anti-NMDAR encephalitis

Abstract

© Author(s) (or their employer(s)) 2021. No commercial reuse. See rights and permissions. Published by BMJ. A young adult male patient presented with subacute onset, rapidly progressive cognitive impairment and refractory seizures and was diagnosed as definite anti Nmethyl Daspartate receptor (antiNMDAR) antibody encephalitis as per criteria by Graus et al. (2016), following detection of culprit autoantibodies in serum. MRI of brain revealed bilateral T2weighted image (T2WI)/fluidattenuated inversion recovery (FLAIR) claustrum hyperintensities (figure 1). Previously, in a cohort of 34 patients, presenting with newonset refractory epilepsy, 4 out of 34 patients showed bilateral claustrum FLAIR hyperintensities on MRI imaging, none of whom were positive for antibodies to onconeural antigens. All these patients had medically intractable epilepsies in whom repeat imaging revealed resolution of radiological abnormalities, despite ongoing seizures. Radiological involvement of biinsular cortex has previously been reported in context of antiNMDAR encephalitis. However, in our case, no insular changes were noticeable along with claustrum hyperintensities. The patient succumbed to autonomic failure despite immunotherapy. Claustrum is a thin sheet of grey matter lying underneath the surface of the insular cortex having widespread connections with neocortical and subcortical structures. A previous study be Meletti et al had implicated bilateral claustrum hyperintensity as a radiological marker of a possible immunemediated epileptogenesis. However, none of the cases in their cohort were found to be positive for autoantibodies. In the absence of largescale studies, it would be premature to presume that this radiological finding may be predictive of an autoantibody such as antiNMDAR and hence, it is paramount for such associations to be reported.