Hashimoto’s encephalopathy revealed by behavioral disorder: A case reportof a new pediatric observation

Authors

Abstract

Hashimoto’s encephalopathy (HE) is defined by the association of encephalopathy and increased thyroid antibodies, with various modes of presentation. However, behavioral disturbances are rare and exceptionally revealing in pediatrics. We report the case of an 11-year-old girl with no significant medical history, admitted to the pediatric neurology unit for behavioral disturbances, preceded a few days earlier by a convulsive episode resembling an absence seizure. The biological workup was normal, and the radiological assessment revealed no abnormalities. Immunological tests showed an elevation of anti-thyroperoxidase antibodies. The diagnosis of Hashimoto’s encephalopathy was made, and the patient was treated with a corticosteroid bolus, with favorable progression. Hashimoto’s encephalopathy is a rare disease; cases have been reported starting from 14 months of age, although it most frequently affects adolescents, with a peak at 14 years old. Clinical manifestations include confusion, decreased consciousness, cognitive deficits, seizures, myoclonus, ataxia, and focal neurological signs. Given the wide variety of symptoms, clinical suspicion is essential. The association of elevated thyroid antibodies with neurological signs is rare, and the diagnosis of Hashimoto’s encephalopathy can be difficult to confirm. Although it may seem excessive, this diagnosis should be considered in the absence of other causes of encephalopathy, as it justifies corticosteroid treatment, and a favorable response can serve as a recurrent diagnostic criterion.

Keywords

Case Presentation

This concerns an 11-year-old girl with no significant medical history, admitted to the pediatric neurology department for behavioral disturbances, which were preceded by a 20-day history of a seizure episode, resembling an absence seizure. Upon admission, her Glasgow Coma Scale (GCS) was 15. She presented with behavioral disturbances, including hetero-aggressiveness and incoherent speech. The rest of the neurological examination was unremarkable. Her vital signs were stable, she was hemodynamically stable, and afebrile. There were no meningeal signs or focal deficits. The initial biological tests were normal, including renal and liver function, C-reactive protein, sedimentation rate, toxicology screens for blood and urine, and viral serologies (hepatitis, cytomegalovirus, Epstein-Barr virus, HIV, herpes, rabies) as well as metabolic testing. Brain MRI and CSF examination were normal. EEG showed normal background activity with diffuse slow wave bursts predominantly in the anterior regions. Further investigations, including a serum and CSF profile for autoimmune encephalitis (anti-NMDA antibodies), were normal. Ophthalmological examination was normal. The patient was treated with intravenous immunoglobulins (2g/kg) without improvement. Testing revealed elevated anti-thyroperoxidase (anti-TPO) antibodies (54.5 UI/ml, normal: < 5.6 UI/ml). The thyroid profile was normal (TSH: 3.2 µUI/ml, range: 0.7-6.4 µUI/ml), and the cervical ultrasound was normal. A diagnosis of Hashimoto’s encephalopathy (HE) was made, and treatment with intravenous methylprednisolone bolus (30mg/kg/day) was initiated, with a spectacular response to steroid treatment after 5 days. The patient was discharged from the hospital and had a favorable outcome without relapse after 3 months.

Discussion

Hashimoto’s encephalitis, or encephalitis associated with autoimmune thyroiditis (Steroid Responsive Encephalopathy Associated with Autoimmune Thyroiditis, SREAT), is a rare condition in children, with a prevalence estimated at 2/100,000 ³. It is defined by:
-An encephalitic presentation with cognitive disturbances, behavioral problems, neuropsychiatric signs (paranoia, hallucinations, psychosis), partial or generalized seizures, focal neurological deficits, consciousness disturbances, and dystonia.
-Elevated serum levels of anti-thyroperoxidase (anti-TPO) antibodies.
-Exclusion of other infectious, toxic, metabolic, autoimmune, or neoplastic causes.
-An effective response to corticosteroid therapy, either partial or complete.
Chronic forms, such as cerebellar syndrome, have been described, as well as myelopathies. These children are often hospitalized for recurrent, drug-resistant seizures or for behavioral problems and abnormal movements with no apparent cause. CSF analysis usually shows hyperproteinorachia, and EEG is almost always abnormal, showing either generalized background slowing or focal abnormalities. In 50% of cases, brain imaging reveals nonspecific abnormalities involving both white and gray matter. Regarding thyroid status, children are often euthyroid. A systematic measurement of anti-TPO antibodies is therefore necessary in cases of unexplained encephalopathy. Anti-TPO antibody levels are elevated and significantly higher than in typical pediatric Hashimoto’s thyroiditis. The pathophysiology of this disease is still unknown, but several theories have been proposed, such as cerebral vasculitis with or without immune complex deposition, leading to disruption of the blood-brain barrier. The majority of children with anti-TPO encephalopathy progress to Hashimoto’s thyroiditis, while the reverse is extremely rare ¹. This suggests the involvement of another possibly associated autoantibody, directly responsible for the neurological involvement. Treatment is based on high-dose corticosteroids, with intravenous methylprednisolone bolus (30mg/kg/day) administered for 3 to 5 days, depending on clinical evolution. During the acute phase of the disease, the response to treatment is sometimes spectacular, with an “on/off” pattern ⁵. Depending on the clinical course, oral corticosteroid therapy (1 mg/kg/day for 15 days) may be considered ⁴. Recurrences are possible, and treatment with immunosuppressive agents, such as cyclophosphamide or azathioprine, may be discussed based on clinical evolution, particularly if steroid dependence is observed. The clinical outcome is generally favorable in the majority of cases, but disabling sequelae such as recurrent seizures and cognitive decline have been described ⁵.

Conclusion

Hashimoto’s encephalopathy, a rare yet curable condition in children, remains a poorly understood and often overlooked disease, lacking clear diagnostic criteria. Keeping this diagnosis in mind could allow for its consideration and confirmation. Advances in fundamental immunology have enabled a better understanding of its pathophysiology, though much remains to be clarified.

Declarations

References

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About This Article

Received:

April 8, 2025

Accepted:

June 2, 2025

Published Online:

July 11, 2025