What is the diagnostic approach for Hashimoto's (Hashimoto's thyroiditis) encephalopathy?

From the Guidelines

Hashimoto's encephalopathy diagnosis requires a comprehensive approach including neurologic consultation, MRI of the brain, lumbar puncture, EEG, and blood tests to rule out other conditions. The diagnostic work-up should start with a neurologic consultation to evaluate the patient's symptoms and determine the need for further testing 1.

Key Diagnostic Tests

• MRI of the brain with or without contrast to reveal T2/fluid-attenuated inversion recovery changes typical of autoimmune encephalopathies or limbic encephalitis, although it may be normal in some cases 1
• Lumbar puncture to check cell count, protein, glucose, and perform Gram stain, culture, PCR for HSV and other viral PCRs, cytology, oligoclonal bands, autoimmune encephalopathy, and paraneoplastic panels 1
• EEG to evaluate for subclinical seizures 1
• Blood tests including metabolic panel, CBC, ESR, CRP, ANCA (if suspect vasculitic process), and thyroid panel including TPO and thyroglobulin to rule out concurrent anemia/thrombocytopenia and evaluate thyroid function 1

Importance of Exclusion

It is crucial to rule out other causes of encephalopathy such as infectious, metabolic, toxic, or autoimmune disorders before confirming the diagnosis of Hashimoto's encephalopathy. The presence of elevated anti-thyroid antibodies, particularly anti-thyroid peroxidase or anti-TPO antibodies, and responsiveness to corticosteroid therapy can serve as key diagnostic features.

Clinical Evaluation

A thorough clinical evaluation is essential to identify neurological or psychiatric symptoms such as confusion, seizures, stroke-like episodes, psychosis, or cognitive decline, which are commonly associated with Hashimoto's encephalopathy. The severity of symptoms does not necessarily correlate with antibody levels, and thyroid function may be normal despite the presence of anti-thyroid antibodies.

From the Research

Diagnostic Approach for Hashimoto's Encephalopathy

The diagnostic approach for Hashimoto's encephalopathy involves several key criteria, including:

• Presence of antithyroid antibodies 2, 3, 4, 5, 6
• Neurological symptoms from the cerebrum and/or cerebellum, such as cognitive impairment, psychiatric features, seizures, myoclonus, ataxia, and focal neurological deficits 2, 3, 4, 5, 6
• Significant clinical improvement after the administration of immunomodulation, such as corticosteroids, intravenous immunoglobulin (IVIG), or plasmapheresis 2, 3, 4, 5, 6

Key Considerations

Some important considerations in the diagnostic approach for Hashimoto's encephalopathy include:

• Ruling out other causes of encephalopathy 6
• Normal brain MRI findings are common in patients with Hashimoto's encephalopathy 5
• Elevated protein in cerebrospinal fluid (CSF) is a common abnormality in patients with Hashimoto's encephalopathy 5
• Autoimmune encephalitis and prion disease should be considered in the differential diagnosis due to similar clinical features 5

Diagnostic Criteria

The diagnostic criteria for Hashimoto's encephalopathy can be summarized as follows:

• Presence of neurological clinical manifestations 2, 3, 4, 5, 6
• Presence of increased antithyroid antibodies 2, 3, 4, 5, 6
• Significant clinical improvement after the administration of immunomodulation 2, 3, 4, 5, 6