When Autoimmunity and Vascular Events Collide: A Unique Presentation of Hashimoto's Encephalopathy and Ischemic Stroke.

Hashimoto's encephalopathy (HE) encompasses an umbrella of symptoms, including cognitive decline, seizures, neurological focal deficits, stroke, psychosis, dementia, and coma. Its pathogenesis is not clear, nor is its mechanism by which it causes strokes. A 56-year-old African American female with nodular thyroid disease presented with subacute encephalopathy, amnesia, and bilateral symmetric cerebral watershed strokes in the setting of elevated antithyroid antibodies that clinically improved after immunotherapy. This is a rare reported case of possible autoimmune thyroiditis (AT) presenting with watershed strokes. Thyroid disorders are a risk factor for cerebrovascular disease. Autoimmune thyroiditis increases the risk of stroke in patients with hypothyroid AT due to the higher frequency of atrial fibrillation, large artery atherosclerosis, and hypertension. The pathogenesis of HE is uncertain, but it is believed that it could be autoimmune, vasculitis, and/or hypoperfusion-related. Our patient had three episodes of hypotension, raising concern for global cerebral hypoperfusion due to the microvascular disruption that takes place in HE. HE has a low prevalence but good response to steroids. Considering it as a differential diagnosis in cases of thyroid disease and acute stroke is crucial to promptly make a diagnosis and start treatment.