Hashimoto’s encephalopathy (HE) is a rare neurological condition characterized by impaired brain function. It is an autoimmune disorder, meaning the body’s immune system mistakenly attacks its own healthy brain tissues. This condition affects approximately two individuals out of every 100,000. Despite its name, which suggests a direct link to thyroid issues, the relationship between HE and thyroid hormone levels is not always straightforward. This disorder is sometimes referred to as steroid-responsive encephalopathy associated with autoimmune thyroiditis (SREAT).
The Link to Thyroid Function
Hashimoto’s encephalopathy is connected to Hashimoto’s thyroiditis, another autoimmune condition affecting the thyroid gland. Both disorders involve the presence of antithyroid antibodies, such as anti-thyreoperoxidase (TPO-Ab) and anti-thyroglobulin (Tg-Ab). While these antibodies are found in individuals with HE, they are considered markers of the condition rather than direct causes of the neurological symptoms.
HE is a distinct neurological disorder, separate from the thyroid dysfunction seen in Hashimoto’s thyroiditis. Many individuals diagnosed with HE maintain normal thyroid function, or are euthyroid, despite having these antibodies. This observation supports that the neurological impairment is not a direct result of thyroid hormone imbalances. The exact mechanism of how these antibodies contribute to brain inflammation is still under investigation.
Recognizing the Symptoms
Hashimoto’s encephalopathy presents with a wide spectrum of neurological and psychiatric symptoms. These manifestations can fluctuate significantly among individuals and may progress acutely or gradually over time. Cognitive impairments are common, including issues with memory, concentration difficulties, confusion, disorientation, and in some cases, symptoms resembling dementia.
Psychiatric symptoms can also be prominent, such as personality changes, aggression, delusional behavior, psychosis, paranoia, and hallucinations. Individuals might also experience depression, anxiety, and other behavioral alterations. Neurological signs include seizures, which are common, especially in children.
Other motor symptoms include tremors and myoclonus (sudden muscle jerks). Problems with coordination, known as ataxia, and gait disturbances are also common. Some individuals may experience stroke-like episodes characterized by focal neurological deficits or speech problems, such as transient aphasia. Sleep disturbances, ranging from drowsiness to altered consciousness and even coma, are also reported.
Diagnostic Approaches
Diagnosing Hashimoto’s encephalopathy is often a process of elimination, as its symptoms overlap with many other neurological conditions. Healthcare providers first work to rule out other possible causes for the neurological impairment. Blood tests are used, looking for high levels of thyroid autoantibodies like anti-thyreoperoxidase (TPO-Ab) and anti-thyroglobulin (Tg-Ab).
Thyroid hormone levels are also assessed, though many patients with HE have normal thyroid function. Cerebrospinal fluid (CSF) analysis, obtained through a lumbar puncture, may reveal elevated protein levels or increased immunoglobulin G (IgG).
Neuroimaging, such as Magnetic Resonance Imaging (MRI) of the brain, is performed to exclude structural abnormalities like tumors or strokes, although MRI scans in HE patients often appear normal or show non-specific changes. An electroencephalogram (EEG) measures electrical activity in the brain and can detect generalized slowing or seizure activity, which are common findings in HE. The combination of these tests, alongside the exclusion of other conditions, helps in reaching a diagnosis.
Treatment Pathways
The primary treatment for Hashimoto’s encephalopathy involves corticosteroids, such as prednisone, which are effective due to their anti-inflammatory and immunosuppressive properties. The condition’s responsiveness to these medications is why it is also known as steroid-responsive encephalopathy associated with autoimmune thyroiditis (SREAT). Individuals often show significant improvement, sometimes within days or weeks of starting treatment, though recovery can take several months.
For patients who do not respond sufficiently to corticosteroids or cannot tolerate them, other immunomodulatory therapies are considered. Intravenous immunoglobulin (IVIg) involves administering concentrated antibodies directly into the bloodstream to modulate the immune system’s activity. Plasma exchange, also known as plasmapheresis, is another option where the patient’s blood plasma, containing harmful antibodies, is removed and replaced.
In addition to these immune-modulating treatments, symptomatic therapies are used to manage specific manifestations of HE. These can include anti-seizure medications for controlling seizures or psychiatric medications to address mood disturbances and behavioral changes. While many individuals experience a good recovery, some may require ongoing management or face the possibility of symptom recurrence.