Hashimoto's Encephalopathy

Hashimoto's Encephalopathy

DOI: 10.4018/978-1-5225-9655-4.ch009

Abstract

Hashimoto's encephalopathy is a relapsing encephalopathy occurring in association with Hashimoto's thyroiditis (HT) with high titers of anti-thyroid antibodies. The mechanism of pathogenesis is unknown. Auto-antibodies to α-enolase have been found to be associated with Hashimoto's encephalopathy. Recently, the crucial role of neuro-inflammation in the development of psychological disorders including depression and anxiety has received more attention. Because the majority of patients with Hashimoto's encephalopathy respond to steroids or immuno-suppressant treatment, this condition is now also referred to as “steroid-responsive encephalopathy.” Initial treatment is usually with oral prednisone (50–150 mg/day) or high-dose IV methyl-Prednisolone (1 g/day) for 3-7 days. Thyroid hormone treatment is also included if required. This chapter explores Hashimoto's encephalopathy.
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Introduction

Hashimoto's encephalopathy is an uncommon neurological condition associated with Hashimoto's thyroiditis and characterized by encephalopathy, thyroid autoimmunity, and good clinical response to steroids. It is sometimes referred to as a neuro-endocrine disorder, although the condition's relationship to the endocrine system is widely disputed (Graus et al., 2016).

Originally described in 1966, Hashimoto's encephalopathy remains a somewhat controversial disorder. It is most often characterized by a subacute onset of confusion with altered level of consciousness, seizures, and myoclonus. In contrast to the cognitive dysfunction associated with hypothyroidism or hyperthyroidism, Hashimoto's encephalopathy is believed to be an immune-mediated disorder rather than representing the direct effect of an altered thyroid state on the central nervous system.

Up to the year 2005, there were almost 200 published case reports of Hashimoto's encephalopathy. From 1990 to 2000, 43 cases were published. Since that time, research has expanded and numerous cases are being reported by scientists around the world, suggesting that this rare condition is likely to have been significantly undiagnosed in the past. Over 100 scientific articles on Hashimoto's encephalopathy were published between 2000 and 2013 (Brain, Jellinek, & Ball, 1966).

Definition

Hashimoto's encephalopathy is a relapsing encephalopathy occurring in association with Hashimoto's thyroiditis, with high titers of anti-thyroid antibodies. Clinically, the condition may present one or more symptoms. Onset is often gradual and may go unnoticed by the patient and close associates to the patients. Symptoms sometimes resolve themselves within days to weeks, leaving a patient undiagnosed. For many other patients, the condition may result in ongoing problems with a variety of manifestations, often confusing clinicians due to the diffuse nature of symptoms.

Synonyms

Hashimoto's encephalopathy has also been known by the following alternative names:

  • Steroid-responsive encephalopathy associated with autoimmune thyroiditis (SREAT).

  • Non-vasculitic autoimmune meningo-encephalitis (NAIM)

  • Encephalopathy associated with autoimmune thyroid disease (EAATD)

History

Brain et al. (1966) described the first case of Hashimoto's encephalopathy The patient was a 48-year-old man with hypothyroidism, multiple episodes of encephalopathy, and stroke-like symptoms as well as Hashimoto's thyroiditis confirmed by elevated anti-thyroid antibodies.

Epidemiology

The prevalence has been estimated to be 2.1/100,000 with a male to female ratio of 1:4. The mean age of onset is 44 with 20% of cases presenting before the age of 18 years (Fujii et al., 2005). Most reported cases occur during the patient's fifth decade of life.

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