Hashimoto's encephalopathy presenting as pseudobulbar palsy.

Introduction: Hashimoto's encephalopathy (HE) is an autoimmune condition with varied neurological and psychiatric features. HE is very unusual as a cause of pseudobulbar palsy (PSP).

Case Presentation: A 14-year-old male was admitted with right-sided weakness, dysphagia, speech disorder, and aggressiveness. Brain magnetic resonance imaging showed increased intensity in bilateral temporal, insular cortex, amygdala, and parahippocampal area on T2-weighted and fluid-attenuated inversion recovery images. Autoimmune encephalitis was considered as the patient had subacute onset of psychiatric and motor disturbances with normal findings for cerebrospinal fluid. N-methyl-D-aspartate receptor, anti-glutamate-type α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid 1 and 2, anti-contactin-associated protein-like 2, anti-gamma-aminobutyric acid receptor, anti-Leucine-rich, and glioma-inactivated 1 antibodies were negative but the anti-thyroperoxidase (antiTPO) level was greater than 998 IU/ML (n:0-9). Steroid therapy was initiated as pulse therapy and maintained with 2-mg/kg/day dose with the diagnosis of HE. He was symptom free for 6 months. In the follow-up period, he had two recurrences which responded to steroid therapy.

Conclusion: The common causes of PSP are demyelinating, vascular, and motor neuron diseases and congenital malformations of the opercular or insular cortex. However, there are no cases of PSP developing after any autoimmune encephalitis. This case highlights the importance of early detection of antiTPO antibodies with the findings of PSP due to autoimmune encephalitis.