Prolonged Conscious Disturbance in a Patient with Neuronal Intranuclear Inclusion Disease Masquerading as Hashimoto Encephalopathy: A Case Report.

We report a 72-year-old female presenting with acute consciousness disturbance, ultimately diagnosed with Neuronal Intranuclear Inclusion Disease (NIID) masquerading as Hashimoto encephalopathy. Comprehensive evaluations revealed elevated antithyroid peroxidase antibodies, characteristic magnetic resonance imaging findings, and genetic confirmation of NIID. Corticosteroid treatment led to partial improvement, but persistent symptoms highlighted the complex presentation of NIID. This rare clinical presentation underscores the importance of thorough diagnostic approaches in complex neurological cases and the challenges in differentiating neurodegenerative disorders from autoimmune conditions. Further studies are necessary to better understand the clinical presentations of these conditions and to develop targeted treatments.