Claustrum hyperintensities: A potential clue to autoimmune epilepsy

In a cohort of 34 patients with autoimmune limbic encephalitis and/or epilepsy, we identified 4 patients exhibiting claustrum fluid‐attenuated inversion recovery (FLAIR) hyperintensities. All 4 patients presented with explosive onset of seizures and developed medically intractable epilepsy, and 2 exhibited a marked response to immunotherapy. Associated features included cognitive and behavioral disturbances (4/4), cerebrospinal fluid (CSF) lymphocytic pleocytosis (3/4), and a neural autoantibody (2/4). Electroencephalogram (EEG) features consisted of slow wave activity and epileptiform discharges in frontal and parasagittal regions, where ictal patterns were captured in 1 patient. In 1 patient, magnetoencephalographic source imaging of interictal spikes revealed dipole sources in anterior insular or subinsular localizations, mirroring claustrum FLAIR hyperintensities, which developed after a short lag from presentation and resolved in all but 1 patient. These MRI abnormalities were isolated (2/4) or associated with mesial temporal hyperintensities (2/4). Claustrum FLAIR hyperintensities may be a useful MRI marker of autoimmune epilepsy.