Case Presentation: A 75-year-old African-American female with a past medical history of hypothyroidism, hypertension, and Alzheimer’s dementia presented to the emergency room with altered mental status and concern for possible stroke; family also reported new seizure-like activity. Vitals on admission were significant for severe hypertension however, she was afebrile. Physical exam was limited due to altered mental status but revealed conjugate gaze, equal and reactive pupils, no murmurs, diminished strength in the left upper extremity, benign thyroid exam, and diffusely warm extremities. Pertinent labs revealed elevated levels of white blood cell count, creatinine kinase, creatinine, thyroid stimulating hormone (TSH), and anti-thyroid peroxides antibody (ant-TPO). Following a head commuted tomography, which was negative for an acute process, brain magnetic resonance imaging was completed and showed left sided enhancement, negative for acute stroke, but concerning for an underlying inflammatory process. Further work up, including two lumbar punctures, for rheumatologic and infectious etiologies remained unrevealing. The patient continued to seize during the early part of her hospitalization, in addition to experience aggressiveness and agitation. With elevated anti-TPO and TSH levels, she was resumed on levothyroxine and started on a high dose of steroids with concern for hashimoto’s encephalopathy due to thyroiditis in the setting of new onset neurologic and psycpsychiatric changes. Throughout the remainder of her hospitalization, the patient showed significant signs of mental status improvement, eventually returning to baseline, and remained seizure free. Her anti-TPO levels continued to decline and she had resolution of her agitated and aggressive behavior as well. Following continued improvement, she was discharged home with a steroid taper and gradual increase in levothyroxine dose.

Discussion: This case is an example of a manifestation for an uncommon disease that is not fully understood. Other diseases, such as vasculitis and myxedema coma, remain a possibility when making this diagnosis given the patient’s significant response to steroids. However, imaging and lab findings assisted in ruling out an alternative etiology; following an involved diagnostic work up for altered mental status in the setting of thyroiditis, it is highly suggestive of Hashimoto’s encephalopathy. Treatment guidance thus hinges on the patient response to steroids and to an extent, an improvement in laboratory findings over time.

Conclusions: Hashimoto’s encephalopathy, also known as steroid responsive encephalopathy associated with autoimmune thyroiditis (SREAT), is a rare disorder characterized by psychiatric and neurologic findings in the setting of thyroiditis. Not well understood, it can be a challenging diagnosis to make, especially given its non-specific presentation. As such, early treatment upon diagnosis is necessary to improve survival outcomes and promote a steady recovery.