Rationale: Hashimoto's encephalopathy (HE) is associated with autoimmune thyroid disease and is complex, diverse, and easily misdiagnosed. However, if HE is diagnosed and treated in a timely manner, an optimal prognosis may be achieved.
Patient concerns: We presented a case of a 63-year-old female patient with paroxysmal dizziness, unsteady gait, emotion apathy, progressive cognitive impairment, and unusual magnetic resonance imaging (MRI) findings.
Diagnoses: After suffering for almost 8 years, the patient was diagnosed with HE based on clinical manifestation, abnormal electroencephalogram, unusual MRI findings, sensitivity to cortisol treatment, and characteristic high antithyroid peroxidase antibody (TpoAb) titer.
Interventions: The patient continued regular glucocorticoids therapy after intravenous methylprednisolone pulse therapy, neurotrophic drugs, traditional Chinese medicine and rehabilitation to relieve hypermyotonia and cognitive impairment.
Outcomes: After combined treatment, the patient's symptoms, electroencephalogram (EEG), MRI, and the TpoAb titer gradually improved. However, the patient had to stop glucocorticoids treatment because of severe osteoporosis, fractures and other adverse reactions. Her symptoms fluctuated, and her TpoAb titer increased again.
Lessons: HE may cause highly heterogeneous clinical features, particularly MRI findings. Withdrawal of the systematic glucocorticoids treatment can lead to varied outcomes in these patients.