biology

Hashimoto's encephalopathy

Hashimoto's encephalopathy is a biology topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Hashimoto's encephalopathy rather than just read about it. In short: Hashimoto's encephalopathy, also known as steroid-responsive encephalopathy associated with autoimmune thyroiditis (SREAT), is a neurological condition characterized by encephalopathy, thyroid autoimmunity, and good clinical response to corticosteroids. It is associated with Hashimoto's thyroiditis, and was first described in 1966.

Key takeaways

Hashimoto's encephalopathy belongs to biology; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Hashimoto's encephalopathy to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Hashimoto's encephalopathy from memory before moving on to harder problems.

Reference excerpt

Hashimoto's encephalopathy, also known as steroid-responsive encephalopathy associated with autoimmune thyroiditis (SREAT), is a neurological condition characterized by encephalopathy, thyroid autoimmunity, and good clinical response to corticosteroids. It is associated with Hashimoto's thyroiditis, and was first described in 1966. It is sometimes referred to as a neuroendocrine disorder, although the condition's relationship to the endocrine system is widely disputed. It is recognized as a rare disease by the NIH Genetic and Rare Diseases Information Center. Up to 2005, almost 200 case reports of this disease were published. Between 1990 and 2000, 43 cases were published. Since that time, research has expanded and numerous cases are being reported by scientists around the world, suggesting that this rare condition is likely to have been significantly undiagnosed in the past. Over 100 scientific articles on Hashimoto's encephalopathy were published between 2000 and 2013.

Signs and symptoms The onset of symptoms tends to be fairly gradual and to occur over 1–12 years. Symptoms of Hashimoto's encephalopathy may include:

Personality changes Aggression Delusional behavior Concentration and memory problems Coma Disorientation Headaches Jerks in the muscles (myoclonus – 65% of cases) Lack of coordination (ataxia – 65% of cases) Partial paralysis on the right side Psychosis Seizures (60% of cases) Sleep abnormalities (55% of cases) Speech problems (transient aphasia – 80% of cases) Status epilepticus (20% of cases) Tremors (80% of cases)

Pathogenesis The mechanism of pathogenesis is not known, but is thought to be an autoimmune disorder, similar to Hashimoto's thyroiditis, as its name suggests. Consistent with this hypothesis, autoantibodies to alpha-enolase have been found to be associated with Hashimoto's encephalopathy. Since enolase is the penultimate step in glycolysis, if it were inhibited (for example by being bound by autoantibodies), one would expect decreased energy production by each cell, leading to resulting atrophy of the affected organ. This would occur most likely through each cell shrinking in size in response to the energy deficit (and/or in extreme situations from some cells dying via either apoptosis or necrosis, depending on location). This may occur as a result of enough ATP not being available to maintain cellular functions - notably, failure of the Na/K ATPase, resulting in a loss of the gradient to drive the Na/Ca antiporter, which normally keeps Ca+2 out of cells so it does not build to toxic levels that will rupture cell lysosomes leading to apoptosis. An additional feature of a low-energy state is failure to maintain axonal transport via dynein/kinesin ATPases, which in many diseases results in neuronal injury to both the brain and/or periphery.

Pathology Very little is known about the pathology of Hashimoto's encephalopathy. Autopsies of some individuals have shown lymphocytic vasculitis of venules and veins in the brainstem and a diffuse gliosis involving gray matter more than white matter. As mentioned above, autoantibodies to alpha-enolase associated with Hashimoto's encephalopathy have thus far been the most hypothesized mechanism of injury.

Diagnosis

Laboratory and radiological findings Increased liver enzyme levels (55% cases) Increased thyroid-stimulating hormone (55% cases) Increased erythrocyte sedimentation rate (25% cases) Cerebrospinal fluid findings:

Raised protein (25% cases) Negative for 14–3–3 protein May contain antithyroid antibodies Magnetic resonance imaging abnormalities consistent with encephalopathy (26% of cases) Single photon emission computed tomography shows focal and global hypoperfusion (75% of cases) Cerebral angiography is normal Thyroid hormone abnormalities are common (>80% of cases):

Subclinical hypothyroidism (35% of cases) Overt hypothyroidism (20% of cases) Hyperthyroidism (5% of cases) Euthyroid on levothyroxine (10% of cases) Euthyroid not on levothyroxine (20% of cases) Thyroid antibodies – both antithyroid peroxidase antibodies (anti-TPO, antithyroid microsomal antibodies, anti-M) and antithyroglobulin antibodies (anti-Tg) – in the disease are elevated, but their levels do not correlate with the severity. Electroencephalogram studies, while almost always abnormal (98% of cases), are usually not diagnostic. The most common findings are diffuse or generalized slowing or frontal intermittent rhythmic delta activity. Prominent triphasic waves, focal slowing, epileptiform abnormalities, and photoparoxysmal and photomyogenic responses may be seen. A study from 2006 suggested the following diagnostic criteria:

Encephalopathy with cognitive impairment and at least one of the following features: neuropsychiatric symptoms (e.g. hallucination, delusion or paranoia) Myoclonus, generalised tonic-clonic or partial seizures focal-neurological deficits Elevated titres of thyroid tissue antibodies (TPO-ab or microsomal) Euthyroidism (potentially achieved by treatment with L-T4 or L-T3) or mild hypothyroidism with TSH concentration below 20 mIU/L No evidence for infectious, toxic, metabolic or neoplastic processes in blood, urine or CSF analyses No serological evidence for neuronal antibodies (e.g. voltage-gated calcium channel, voltage-gated potassium channel, or other currently recognized paraneoplastic antibodies) to support another diagnosis In imaging studies no evidence for vascular, neoplastic or structural lesions that might explain the symptoms Complete or nearly complete remission after initiation of glucocorticoid therapy.

Definition A relapsing encephalopathy occurs in association with autoimmune (Hashimoto's or Ord's thyroiditis), with high titers of antithyroid antibodies. Clinically, the condition may present one or more symptoms. Onset is often gradual and may go unnoticed by the patient and close associates to the patients. Symptoms sometimes resolve themselves within days to weeks, leaving a patient undiagnosed. For many other patients, the condition may result in ongoing problems with a variety of manifestations, often confusing clinicians due to the diffuse nature of symptoms.

Differential diagnosis

… excerpt ends here. Continue reading the full article.

Illustrations

Worked examples

Example 1 — a first encounter with Hashimoto's encephalopathy

Start with the simplest possible case. Write down what Hashimoto's encephalopathy claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In biology, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Hashimoto's encephalopathy before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Hashimoto's encephalopathy ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Hashimoto's encephalopathy

In research: Hashimoto's encephalopathy appears in biology research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Hashimoto's encephalopathy in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Hashimoto's encephalopathy is common in secondary-school and first-year university syllabi. It links to neighbouring topics Autoimmune diseases, Brain disorders, Neuroendocrinology, so understanding it makes those chapters shorter.
In everyday life: Look for Hashimoto's encephalopathy outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Hashimoto's encephalopathy in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Hashimoto's encephalopathy means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Hashimoto's encephalopathy out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Hashimoto's encephalopathy in simple terms?

Why does Hashimoto's encephalopathy matter?

Because it connects several biology ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Hashimoto's encephalopathy?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Hashimoto's encephalopathy.