Hashimoto's encephalopathy
Authors: SE Taylor, G Tudor-Williams, ME Garalda, N Martinez-Alier
Journal: The Lancet (2003)

Authors' reply Sir—As in the case quoted by Ajit Kashyap and Surekha Kashyap,1Ishii K Hayashi A Tamaoka A et al.Case report: thyrotropin-releasing hormone induced myoclonus and tremor in a patient with Hashimoto's encephalopathy.Am J Med Sci. 1995; 310: 202-205Crossref PubMed Scopus (22) Google Scholar our patient's symptoms were cyclical to some extent, but worsened during menstruation rather than after ovulation. The importance of this association is unclear. Kashyap and Kashyap also draw attention to a case report in which intravenous administration of thyrotropin-releasing hormone induced symptoms of myoclonus and tremor similar to those observed during an exacerbation in a patient with Hashimoto's encephalopathy. Symptoms were reversed with thyroxine-replacement therapy. Our patient had normal thyroid function, so we did not investigate a possible role of thyrotropin releasing hormone in disease pathogenesis. Furthermore, most reports of patients with Hashimoto's encephalopathy indicate that the individuals were euthyroid (some on thyroxine supplements) at the time of disease onset. When hypothyroid, patients did not improve with supplements, and actually relapsed while on thyroxine. Jayne Franklyn notes the high prevalence of thyroid autoantibodies in women of reproductive age, and suggests that our patient's symptoms, and those of others diagnosed with Hashimoto's encephalopathy, could be explained by a concomitant autoimmune disorder. She has a valid point, and we were open to this possibility in our patient, especially in view of the strong family history of thyroid disease. However, an autoimmune screen at the time of her acute presentation was negative, and serum complement concentrations were normal. Associated autoimmune antibodies—other than those against the thryoid—have been recorded in only about 25% of patients, the rest having a documented negative autoimmune screen.2Shaw PJ Walls TJ Newman PK Cleland PG Cartlidge NEF Hashimoto's encephalopathy: a steroid-responsive disorder associated with high anti-thyroid antibody titres—report of 5 cases.Neurology. 1991; 41: 228-233Crossref PubMed Google Scholar The proportion of individuals in the general population with low concentrations of detectable thyroid microsomal antibodies may be high, but the proportion with concentrations of antibodies against thyroid peroxidase greater than 1000 IU/mL is extremely low. In a study, for example, of 660 healthy children and adolescents in Berlin, only ten individuals had values higher than 1000 IU/mL.3Kabelitz M Liesenkotter KP Stach B et al.The prevalence of anti-thyroid peroxidase antibodies and autoimmune thyroiditis in children and adolescents in an iodine replete area.Eur JEndocrinol. 2003; 148: 301-307Crossref PubMed Scopus (99) Google Scholar Furthermore, Franklyn's opening statement has omitted the third positive investigation required to make a diagnosis of Hashimoto's encephalopathy—an encephalopathic electroencephalogram, which is documented in 90% of paediatric cases.4Kothbauer-Margreiter I Sturzenegger M Komor J Baumgartner R Hess CW Encephalopathy associated with Hashimoto thyroiditis: diagnosis and treatment.J Neurol. 1996; 243: 585-593Crossref PubMed Scopus (322) Google Scholar Our case had a persistently encephalopathic EEG, which greatly improved within 12 days of starting steroid treatment. In response to the point raised with respect to "how an encephalopathic illness could reflect Hashimoto's thyroiditis in the presence of normal thyroid function", we reiterate that Hashimoto's encephalopathy is a different entity to Hashimoto's thyroiditis, and does not require abnormal thyroid function to establish a diagnosis. The pathophysiology of Hashimoto's encephalopathy is poorly understood. As indicated in the correspondence, various mechanisms have been proposed, including endocrine derangement, an autoimmune process, and a vasculitic phenomena.5Wattemberg N Willis D Pellock J Encephalopathy as the presenting symptom of Hashimoto's thyroiditis.J Child Neurol. 2000; 15: 66-69Crossref PubMed Scopus (28) Google Scholar Support for the cerebral vasculitis hypothesis derives from the presence in some reported cases of stroke-like events, raised erythrocyte sedimentation rates, and abnormal angiography. Should autoimmune processes be paramount, follow-up of paediatric cases might be expected to reveal the development of other autoimmune disorders. Hashimoto's encephalopathyIn their excellent Case report of Hashimoto's encephalopathy in a 14-year-old girl (Feb 15, p 572),1 Sharon Taylor and colleagues do not indicate whether the patient's symptoms are related to her menstrual cycles. Ishii and co-workers2 reported a case of a 43-year-old Japanese woman who had three relapses closely associated with her menstrual cycle; her symptoms began at ovulation, worsened during the luteal phase, and improved during menstruation. Moreover, Taylor and colleagues do not discuss the important role of thyrotropin-releasing hormone as a possible cause of Hashimoto's encephalopathy. Full-Text PDF Hashimoto's encephalopathySharon Taylor and colleagues1 describe a steroid-responsive neuropsychiatric illness in a 14-year-old girl. A diagnosis of Hashimoto's encephalopathy was made based on the presence of a high titre of antibodies against thyroid peroxidase and a small goitre. Full-Text PDF