|Other names: Steroid-responsive encephalopathy associated with autoimmune thyroiditis, Nonvasculitic autoimmune meningoencephalitis, Encephalopathy associated with autoimmune thyroid disease, EAATD|
|Brain SPECT transaxial images of a patient afflicted with Hashimoto's encephalopathy.|
Hashimoto's encephalopathy, also known as steroid-responsive encephalopathy associated with autoimmune thyroiditis (SREAT), is a neurological condition characterized by encephalopathy, thyroid autoimmunity, and good clinical response to corticosteroids. It is associated with Hashimoto's thyroiditis, and was first described in 1966. It is sometimes referred to as a neuroendocrine disorder, although the condition's relationship to the endocrine system is widely disputed. It is recognized as a rare disease by the NIH Genetic and Rare Diseases Information Center.
Almost 200 case reports of this disease have been published.
Signs and symptoms
- Personality changes
- Delusional behavior
- Concentration and memory problems
- Poor appetite
- Lack of coordination
- Slurred speech
- Sleep abnormalities
- Status epilepticus
A relapsing encephalopathy occurs in association with Hashimoto's thyroiditis, with high titers of antithyroid antibodies. Onset is often gradual and may go unnoticed by the individual and close associates to the individual; symptoms sometimes resolve themselves, leaving the individual undiagnosed.
The cause is not known, but is thought to be an autoimmune disorderConsistent with this hypothesis, autoantibodies to alpha-enolase have been found to be associated with Hashimoto's encephalopathy.
Enolase has been found in the brain tissue of individuals with HE and is the penultimate step in glycolysis, if it were inhibited, one would expect decreased energy production by each cell, leading to resulting atrophy of the affected organ.This would occur most likely through each cell shrinking in size in response to the energy deficit.This may occur as a result of enough ATP not being available to maintain cellular functions - notably, failure of the Na/K ATPase, resulting in a loss of the gradient to drive the Na/Ca antiporter, which normally keeps Ca+
2 out of cells so it does not build to toxic levels that will rupture cell lysosomes leading to apoptosis. An additional feature of a low-energy state is failure to maintain axonal transport via dynein/kinesin ATPases, which in many diseases results in neuronal injury to both the brain and/or periphery.
Very little is known about the pathology of Hashimoto's encephalopathy, post mortem studies of some individuals have shown lymphocytic vasculitis of venules and veins in the brain stem As mentioned above, autoantibodies to alpha-enolase associated with Hashimoto's encephalopathy have thus far been the most hypothesized mechanism of injury.
In terms of the diagnosis of Hashimoto's encephalopathy electroencephalogram studies, while almost always abnormal, are usually not diagnostic. The most common findings are diffuse or generalized slowing or frontal intermittent rhythmic delta activity. Prominent triphasic waves, focal slowing, epileptiform abnormalities, and photoparoxysmal and photomyogenic responses may be seen.
- Raised protein
- May contain antithyroid antibodies
- Magnetic resonance imaging abnormalities consistent with encephalopathy
- Cell count normal
- Cerebral angiography is normal
Thyroid hormone abnormalities are common : 
- Subclinical hypothyroidism
- Overt hypothyroidism
Because most individuals respond to corticosteroids or immunosuppressant treatment, this condition is now also referred to as steroid-responsive encephalopathy.Initial treatment is usually with oral prednisone (30 mg/day) or high-dose intravenous methylprednisolone (1 g/day) for 5 days. Thyroid hormone treatment is also included if required, failure of some individuals to respond to this first-line treatment has produced a variety of alternative treatments, including azathioprine, cyclophosphamide, methotrexate, periodic intravenous immunoglobulin, and plasma exchange.Seizures, if present, are controlled with typical antiepileptic agents.
Duration of treatment is usually between 2 and 25 years. Earlier reports suggested that 90% of cases stay in remission after discontinuation of treatment, but this is at odds with more recent studies, which suggest that relapse commonly occurs after initial high-dose steroid treatment.
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