Hashimoto's encephalopathy (HE) is a term used by neurologists to describe a syndrome of cerebral symptoms in patients with serologic (presence of thyroid antibodies) evidence of autoimmune thyroid disease. The manifestations of this illness have caused some researchers to question if this is a true syndrome or a condition related to hypothyroidism. Overt hypothyroidism can cause cerebral dysfunction, including decreases in alertness, mood, cognition, and conditions of psychosis (myxedema madness) and coma.
In an effort to determine if Hashimoto's encephalopathy is a true syndrome or coincidental myth, researchers have made an exhaustive search of the literature. The controversy stems from the many subtle causes of impaired cognition and the fact that thyroid function tests as well as thyroid antibody titers vary markedly among subjects presumed to have HE. Neurologic studies are also not always consistent.
Thyroid antibodies seen in HE include TPO, thyroglobulin and TSH receptor antibodies. In the majority of cases determined to be HE, thyroid antibodies have been detected in cerebrospinal fluid. These antibodies have also been seen in patients with Sjogren's syndrome and myasthenia gravis as well as autoimmune thyroid disorders, suggesting the term might be better expressed as autoimmune encephalopathy.
Ji Y. Chong, L. Roland, and Robert Utiger, Hashimoto Encephalopathy, Syndrome or Myth? Archives of Neurology, 2003l 60; 164-171.