Hashimoto's Encephalopathy: A Brief Introduction

Man with headache rubbing forehead
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by Mary Shomon

Hashimoto's Thyroiditis and Hashimoto's Encephalopathy

Hashimoto's thyroiditis is the autoimmune thyroid disease that is the most common cause of hypothyroidism, an underactive thyroid. A very rare condition associated with Hashimoto's thyroiditis is Hashimoto's Encephalopathy (abbreviated as HE). Hashimoto's Encephalopathy is a neuroendocrine disorder whose mechanisms are not clearly understood by doctors and researchers.

It's thought that Hashimoto's disease, Hashimoto's Encephalopathy is autoimmune, and caused by an aggressive but mistaken immune system.

We do know that in Hashimoto's Encephalopathy, high levels of antithyroid antibodies (Thyroid Peroxidase Antibodies, or TPO) appear to be related to a swelling in the brain. 

How Often Does Hashimoto's Encephalopathy Occur?

Hashimoto's Encephalopathy is considered quite rare (there are several dozen diagnosed patients in the United States) but it is likely that there are many more undiagnosed sufferers who are undiagnosed or misdiagnosed. Because it is little known and its symptoms are primarily neurological, it is easy to misdiagnosis or overlook and the symptoms frequently lead to mistaken neurological diagnoses.

While HE is diagnosed within a range of 14 to 78 years of age, 47 is the average age of onset, and most patients are women.The condition can also appear in adolescents, but is even more likely to be overlooked.

The symptoms in adolescents, unlike adults, frequently include seizures, confusion and hallucinations. A drop in school performance is also a common symptom, along with progressive cognitive decline. Thyroid antibody levels should be evaluated in any adolescents with these symptoms, even when other thyroid function tests are normal.

Some of the most common symptoms in adults with Hashimoto's Encephalopathy include the following: disorientation, psychosis, tremors, concentration and memory problems, spasms and jerks in the muscles known as myoclonus, lack of coordination, headaches, partial paralysis on the right side, and speech problems.

The disease often progresses along two avenues--either as an acute, stroke-like attack or seizure, or through progressive movement into dementia, or even coma. Sometimes, patients are mistakenly diagnosed as having had a stroke, Creutzfeldt-Jakob disease, dementia, or Alzheimer's disease.

At present, there is not a definitive test for Hashimoto's Encephalopathy.  While thyroid antibodies may be high, they may also not be present. Similarly, TSH levels could be of concern, or could be normal. Treatment with thyroid hormone replacement medication does not resolve HE, which appears to progress toward chronic inflammation.

Despite the lack of a clear diagnostic test, results from electroencephalography, and cerebrospinal fluid testing usually show out of range results.

Diagnosis of HE is made through exclusion of other disorders.

Treatment of HE

The primary treatment for Hashimoto's Encephalopathy is oral corticosteroid drugs, like Prednisone. Many patients respond dramatically to drug treatment, with an average acute treatment period of four to six weeks. Like all autoimmune disorders at present, HE is not curable. After initial treatment, the disorder often lapses into remission. Some patients are able to discontinue drug therapy for a number of years, although HE is a relapsing condition.

In addition to steroid therapy, other treatments such as intravenous immunoglobulin and plasma exchange are options.

While rare, Hashimoto's Encephalopathy could be the culprit behind depression, sporadic seizure, or even anxiety. It is not until the condition presents itself by acute, or unresponsive neuropsychiatric symptoms, that many doctors look for thyroid issues, nodules, or a family history of immune dysfunction.

Patients who experience Hashimoto's Encephalopathy face a diagnostic challenge and a potentially devastating disease. Fortunately, most people respond to readily available treatment.  If you suffer acute neuro-cognitive symptoms your doctor cannot explain, be sure to mention your history of Hashimoto's Thyroiditis.

Some experts suggest that the condition be renamed to remove the link to Hashimoto's, and instead call it "steroid responsive encephalopathy associated with autoimmune thyroiditis.' 

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