The pathogenesis of HE is uncertain. Available evidences point towards an autoimmune etiology due to
vasculitis or other inflammatory process. Detection of thyroid
antibodies - antithyroid
peroxidase and
anti-thyroglobulin are essential for diagnosis.
Autoimmune encephalitis including Anti-IgLON5 disease needs to be excluded in suspected cases with appropriate tests for neuronal surface
antibodies. Detection of thyroid
autoantibodies is nonspecific, as these can be detected in some normal individuals and in other
autoimmune diseases. In recent years, attention has turned to an aggressive form of Hashimoto's
thyroiditis accompanied by elevated serum
IgG4 levels in younger males with very high levels of thyroid
antibodies. The role of the thyroid
autoantibodies in the central nervous system (CNS) tissue damage remains unclear and these can act only as markers for diagnosis. Conversely, they have a role to play in determining the thyroid pathology - more glandular
fibrosis associated with thyro-
peroxidase antibody than with the
thyroglobulin antibody. HE is a syndrome characterized by altered mental status,
confusion,
hallucinations, delusions, and sometimes
seizures, in association with high serum anti-thyroid antibody concentration that is usually responsive to
glucocorticoid therapy. Diagnosis requires the exclusion of other causes of
encephalopathies and
encephalitis including
autoimmune encephalitis associated with neuronal surface
antibodies and paraneoplastic ones. Diagnosis also is dependent on the demonstration of thyroid
autoantibodies in serum. Since there is no direct pathophysiologic link between antithyroid
antibodies,
Hashimoto thyroiditis and the cerebral syndrome, the nomenclature HE could be misleading. The response to
steroids led to a renaming of the syndrome to
steroid responsive encephalopathy associated with autoimmune thyroiditis (SREAT), though some cases do not respond to
steroids. In recent years, attention has turned to an aggressive form of Hashimoto's
thyroiditis accompanied by elevated serum
IgG4 levels (IgG4-related disease). This is characterized by a higher incidence in men (5:1) than in women, onset at a younger age, more intense thyroid
inflammation and higher antithyroid antibody titters. Such patients have excessive production of IgG4 + plasmacytes, which infiltrate various organs leading to their
fibrosis and
sclerosis, sometimes resulting in inflammatory
tumors. HE is treated with
corticosteroids along with treatment of the dysthyroid condition, if any. There are yet no guidelines regarding
steroid dose and/or duration.