Anti leucine-rich glioma-inactivated 1 (LGI1) antibody-positive limbic encephalitis with evolving basal ganglia T1WI hyperintensity: A case report.

Anti-leucine-rich glioma-inactivated 1 (LGI1) antibody-associated autoimmune encephalitis (anti-LGI1-AE) is a neuronal, surface antibody-mediated type of encephalitis characterized by medial temporal lobe hypertrophy and hyperintensity on T2-weighted images (WI). T1-weighted images (T1WI) can reveal basal ganglia hyperintensity, particularly when patients have faciobrachial dystonic seizures (FBDS). This signal change on T1WI is generally considered to correlate with FBDS. Here, we describe a female patient with FBDS and basal ganglia T1WI hyperintensity in whom imaging abnormalities did not reflect FBDS severity. Although a single observation cannot establish causality, this dissociation raises the possibility that factors other than FBDS activity contribute to altered T1WI signals and that such findings might not always reflect disease activity. Clinicians should be aware that such T1WI changes do not need to parallel FBDS to avoid overinterpreting them as clinical course markers. Further studies are required to clarify these underlying mechanisms.