More than 40 years after its initial description by Brain et al, 'Hashimoto's encephalopathy' (HE) remains an enigmatic clinical entity((1)) .Although no universally accepted definition exists, commonly employed diagnostic criteria include an acute or subacute presentation with neuropsychiatric symptoms consistent with encephalopathy, presence of serum anti-thyroid antibodies and exclusion of alternative infective or metabolic causes((2)) .The vast majority of HE cases described in the literature relate to patients demonstrating either hypothyroidism or euthyroidism((2-5)) . This article is protected by copyright. All rights reserved.