FRI560 A Rare Case Of Hashimoto Encephalopathy

Abstract

Abstract Disclosure: M. Nokhbehzaeim: None. H.K. Driscoll: None. M. Sanati: None. Background: Hashimoto encephalopathy is a rare syndrome associated with Hashimoto’s thyroiditis. It presents as an encephalopathy without central nervous system infection or tumor. It is also described as steroid-responsive encephalopathy. It is characterized by high titers of antithyroid peroxidase antibodies. Case: 60-year-old female, with known Hashimoto thyroiditis on levothyroxine 200 mcg daily was admitted to the hospital with generalized weakness and lethargy. On admission, her TSH level was 0.085 with a Free T4 of 2.15. Subsequently, the Levothyroxine dose was decreased to 175 mcg and then was held for a few days. During her hospital stay her mental status deteriorated, and she became altered. As a part of the work-up, an MRI of the brain was done. It showed nonspecific left-sided dural thickening with enhancement, consistent with meningitis, but no signs of brain metastasis. She also developed persistent plantar flexion of both ankles and staring forward. MRI of Cervical, Thoracic, and Lumbar spine was done and leptomeningeal carcinomatosis was ruled out. She underwent a lumbar puncture; however, the CSF meningitis panel was negative. She was started on a trial of Dexamethasone 4 mg PO q 12 hours for 5 days. Her repeat thyroid function test revealed TSH: 54.4 and normal Free T4: 1.1. Levothyroxine 150 mcg was restarted, and the dose of Levothyroxine was increased to 175 mcg daily. She underwent a brain biopsy, which was unremarkable. Paraneoplastic panel and GAD 65 antibody were not detected. She was started on a trial of methylprednisolone and IVIG, and she showed significant improvement. Discussion: Hashimoto encephalopathy may involve a relapsing and remitting course and include seizures, stroke-like episodes, cognitive decline, neuropsychiatric symptoms, and myoclonus. Thyroid function is usually clinically and biochemically normal. It is characterized by high titers of antithyroid peroxidase antibodies. The other causes of encephalopathy such as toxic, metabolic, and infectious should be excluded with neuroimaging and CSF examination. Common differential diagnoses when these conditions are excluded are Creutzfeldt-Jakob disease, rapidly progressive dementias, and paraneoplastic and nonparaneoplastic limbic encephalitis. It is a rare disorder but it is responsive to treatment with corticosteroids. Clinical improvements are also observed with IV immunoglobulin and plasmapheresis. Presentation: Friday, June 16, 2023