Hashimoto's autoimmune thyroiditis is a common cause of thyroid disease. Neurological dysfunction related to thyroid hypo or hyperfunction is well known. Not so is autoimmune thyroid disease-associated or Hashimoto's encephalopathy, which includes different neurological manifestations appearing in the context of autoimmune thyroiditis with normal hormone levels. Around fifty cases have been reported since the first description by Brain in 1966. Pathogenesis is unknown, although the most accepted theory points out to an autoimmune cerebral dysfunction. There are two different clinical presentations. The vasculitic type is characterized by relapsing-remitting stroke-like episodes. The diffuse-progressive type shows insidious cognitive impairment, confusion, psychosis, somnolence and coma. Cerebrospinal fluid is abnormal in more than 80% of patients, with high protein levels and mononuclear pleocytosis. Steroids are the treatment of choice, although favourable evolution have been reported spontaneously or after thyroxine treatment.