title: Hashimoto's encephalopathy: epidemiologic data and pathogenetic considerations.
abstract: BACKGROUND
  Hashimoto's encephalopathy (HE) is a condition believed to complicate Hashimoto's thyroiditis (HT). The diagnosis is suspected in the presence of high levels of serum anti-thyroid antibodies. We have recently demonstrated that in patients with HE there is an intrathecal synthesis of anti-thyroid antibodies, and concluded that the diagnosis of HE should be based on this cerebrospinal fluid (CSF) finding.
  
  
  OBJECTIVE
  getting an estimate of the prevalence of the disease, verifying the association with HT and investigating the pathogenetic role of anti-thyroid antibodies.
  
  
  METHODS
  34-months prospective study in a hospital setting serving a community of 150,000 people. Patients with unexplained symptoms of acute or subacute encephalopathy or myelopathy or with a history of thyroid disorders were selected for the measurement of anti-thyroid antibodies. In the presence of high serum levels of autoantibodies, the same tests were performed in the CSF.
  
  
  RESULTS
  Twelve patients had increased concentrations of serum autoantibodies but HE was diagnosed only in nine patients. The estimated prevalence of HE is 2.1/100,000. Only six HE patients had also HT. Four patients received corticosteroids, five patients were not treated. Five patients improved, four patients spontaneously, one patient after corticosteroids. Repeated CSF examinations showed that the titer of CSF autoantibodies did not correlate with the clinical stage of the disease nor was influenced by corticosteroids. In addition, the course of symptoms was independent of therapy.
  
  
  CONCLUSIONS
  The association of encephalopathy and high titers of anti-thyroid antibodies is not sufficient to make a diagnosis of HE. Independent of the clinical status of the thyroid gland, the intrathecal synthesis of autoantibodies is a distinctive marker of this elusive condition.
authors.affiliation: Division of Neurology, Ospedale "S. Martino", Viale Europa 32100 Belluno, Italy. franco.ferracii@ulss.bellumo.it
authors.forename: Franco
authors.initials: F
authors.lastname: Ferracci
authors.forename: Gianni
authors.initials: G
authors.lastname: Bertiato
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Moretto
mesh_terms: D000293:Adolescent; D000305:Adrenal Cortex Hormones / Q000627:therapeutic use; D000328:Adult; D000368:Aged; D001323:Autoantibodies / Q000097:blood / Q000134:cerebrospinal fluid* / Q000276:immunology; D001925:Brain Damage, Chronic / Q000134:cerebrospinal fluid* / Q000453:epidemiology / Q000276:immunology*; D002555:Cerebrospinal Fluid / Q000276:immunology* / Q000378:metabolism; D015897:Comorbidity; D005260:Female; D006801:Humans; D007558:Italy / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011446:Prospective Studies; D013961:Thyroid Gland / Q000276:immunology* / Q000503:physiopathology; D013967:Thyroiditis, Autoimmune / Q000453:epidemiology / Q000276:immunology*
chemical_list: D000305:Adrenal Cortex Hormones; D001323:Autoantibodies