- Last edited on July 18, 2023
Hashimoto's Encephalitis (Steroid Responsive Encephalopathy Associated with Autoimmune Thyroiditis [SREAT])
Primer
Hashimoto's Encephalopathy (HE) (also known as Steroid Responsive Encephalopathy Associated with Autoimmune Thyroiditis [SREAT]), is a rare, clinically heterogeneous neurological disorder associated with Hashimoto's disease and positive thyroid autoantibodies. It is is a form of autoimmune encephalitis. It is increasingly recognized as an important and treatable cause of autoimmune encephalitis, though remains somewhat controversial as a diagnosis.
Epidemiology
- HE predominantly affects women in a wide age range, from 10 to 80 years of age.
Comorbidity
- Clinical or subclinical thyroid disease, usually hypothyroidism, occurs in over half of the cases.
Diagnostic Criteria
Diagnosis can be made when all 6 of the following criteria have been met (Graus et al. 2016):[1]
- Encephalopathy with seizures, myoclonus, hallucinations, or stroke-like episodes
- Subclinical or mild overt thyroid disease (usually hypothyroidism)
- Brain MRI normal or with non-specific abnormalities
- Presence of serum thyroid antibodies (thyroid peroxidase, thyroglobulin)
- Absence of well characterized neuronal antibodies in serum and CSF
- Reasonable exclusion of alternative causes (see Differential Diagnosis)
Symptoms
The clinical presentation of HE can include seizures, myoclonus, hallucinations, and stroke-like episodes with normal or non-specific CSF and brain MRI abnormalities.Controversial Diagnosis
Hashimoto’s encephalopathy should be diagnosed only when a thorough clinical assessment has been performed, including comprehensive testing for well characterized neuronal antibodies, and ruling out other potential causes of encephalopathy or encephalitis. In essence, it should be a diagnosis of exclusion.Pathophysiology
Differential Diagnosis
Investigations
- anti-TPO (thyroid peroxidase antibody), anti-thyroglobulin, and anti-dsDNA can be elevated in HE
- Thyroid peroxidase antibody is elevated in over 90% of cases of Hashimoto’s thyroiditis.
- Although the test has a false positive rate of up to 20%, a positive result may indicate SREAT, and should prompt a thorough search for neurological symptoms that might support a diagnosis of encephalopathy.
Thyroid Antibodies Are Non-Specific!
Thyroid antibodies are not specific for Hashimoto’s encephalopathy. They can be present in up to 13% of healthy individuals, and up to 27% in white women older than 60 years. It can also be present in other autoimmune encephalitis disorders.Treatment
Patients with a non-specific encephalopathy with subclinical or overt thyroid disease, anti-thyroid antibodies, and no other explanation for the symptoms should be considered for a trial of steroids. Most patients treated with corticosteroids with or without levothyroxine will have clinical improvement.[2]