biology

Neurosarcoidosis

Neurosarcoidosis 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 Neurosarcoidosis rather than just read about it. In short: Neurosarcoidosis (sometimes shortened to neurosarcoid) refers to a type of sarcoidosis, a condition of unknown cause featuring granulomas in various tissues, in this type involving the central nervous system (brain and spinal cord). Neurosarcoidosis can have many manifestations, but abnormalities of the cranial nerves (a group of twelve nerves supplying the head and neck area) are the most common.

Key takeaways

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

Reference excerpt

Neurosarcoidosis (sometimes shortened to neurosarcoid) refers to a type of sarcoidosis, a condition of unknown cause featuring granulomas in various tissues, in this type involving the central nervous system (brain and spinal cord). Neurosarcoidosis can have many manifestations, but abnormalities of the cranial nerves (a group of twelve nerves supplying the head and neck area) are the most common. It may develop acutely, subacutely, and chronically. Approximately 5–10 percent of people with sarcoidosis of other organs (e.g. lung) develop central nervous system involvement. Only 1 percent of people with sarcoidosis will have neurosarcoidosis alone without involvement of any other organs. Diagnosis can be difficult, with no test apart from biopsy achieving a high accuracy rate. Treatment is with immunosuppression. The first case of sarcoidosis involving the nervous system was reported in 1905.

Signs and symptoms

Neurological Abnormalities of the cranial nerves are present in 50–70 percent of cases. The most common abnormality is involvement of the facial nerve, which may lead to reduced power on one or both sides of the face (65 percent resp 35 percent of all cranial nerve cases), followed by reduction in visual perception due to optic nerve involvement. Rarer symptoms are double vision (oculomotor nerve, trochlear nerve or abducens nerve), decreased sensation of the face (trigeminal nerve), hearing loss or vertigo (vestibulocochlear nerve), swallowing problems (glossopharyngeal nerve) and weakness of the shoulder muscles (accessory nerve) or the tongue (hypoglossal nerve). Visual problems may also be the result of papilledema (swelling of the optic disc) due to obstruction by granulomas of the normal cerebrospinal fluid (CSF) circulation. Seizures (mostly of the tonic-clonic/"grand mal" type) are present in about 15 percent and may be the presenting phenomenon in 10 percent. Meningitis (inflammation of the lining of the brain) occurs in 3–26 percent of cases. Symptoms may include headache and nuchal rigidity (being unable to bend the head forward). It may be acute or chronic. Accumulation of granulomas in particular areas of the brain can lead to abnormalities in the function of that area. For instance, involvement of the internal capsule would lead to weakness in one or two limbs on one side of the body. If the granulomas are large, they can exert a mass effect and cause headache and increase the risk of seizures. Obstruction of the flow of cerebrospinal fluid, too, can cause headaches, visual symptoms (as mentioned above) and other features of raised intracranial pressure and hydrocephalus. Involvement of the spinal cord is rare, but can lead to abnormal sensation or weakness in one or more limbs, or cauda equina symptoms (incontinence to urine or stool, decreased sensation in the buttocks).

Endocrine Granulomas in the pituitary gland, which produces numerous hormones, are rare but may lead to any of the symptoms of hypopituitarism: amenorrhoea (cessation of the menstrual cycle), diabetes insipidus (dehydration due to inability to concentrate the urine), hypothyroidism (decreased activity of the thyroid) or hypocortisolism (deficiency of cortisol).

Mental and other Psychiatric problems occur in 20 percent of cases; many different disorders have been reported, e.g. depression and psychosis. Peripheral neuropathy has been reported in up to 15 percent of cases of neurosarcoidosis. Other symptoms due to sarcoidosis of other organs may be uveitis (inflammation of the uveal layer in the eye), dyspnoea (shortness of breath), arthralgia (joint pains), lupus pernio (a red skin rash, usually of the face), erythema nodosum (red skin lumps, usually on the shins), and symptoms of liver involvement (jaundice) or heart involvement (heart failure).

Pathophysiology

Sarcoidosis is a disease of unknown cause that leads to the development of granulomas in various organs. While the lungs are typically involved, other organs may equally be affected. Some subforms of sarcoidosis, such as Löfgren syndrome, may have a particular precipitant and have a specific course. It is unknown which characteristics predispose sarcoidosis patients to brain or spinal cord involvement.

Diagnosis

The diagnosis of neurosarcoidosis often is difficult. Definitive diagnosis can only be made by biopsy (surgically removing a tissue sample). Because of the risks associated with brain biopsies, they are avoided as much as possible. Other investigations that may be performed in any of the symptoms mentioned above are computed tomography (CT) or magnetic resonance imaging (MRI) of the brain, lumbar puncture, electroencephalography (EEG) and evoked potential (EP) studies. If the diagnosis of sarcoidosis is suspected, typical X-ray or CT appearances of the chest may make the diagnosis more likely; elevations in angiotensin-converting enzyme and calcium in the blood, too, make sarcoidosis more likely. In the past, the Kveim test was used to diagnose sarcoidosis. This now obsolete test had a high (85 percent) sensitivity, but required spleen tissue of a known sarcoidosis patient, some of which was injected into the skin of a suspected case. Only biopsy of suspicious lesions in the brain or elsewhere is considered useful for a definitive diagnosis of neurosarcoidosis. The tissue sample would demonstrate granulomas (collections of inflammatory cells) rich in epithelioid cells and surrounded by other immune system cells (e.g. plasma cells, mast cells). Biopsy may be performed to distinguish mass lesions from tumours (e.g. gliomas). MRI with gadolinium enhancement is the most useful neuroimaging test. This may show enhancement of the pia mater or white matter lesions that may resemble the lesions seen in multiple sclerosis. Lumbar puncture may demonstrate raised protein level, pleiocytosis (i.e. increased presence of both lymphocytes and neutrophil granulocytes) and oligoclonal bands. Various other tests (e.g. ACE level in CSF) have little added value.

Criteria Some recent papers propose to classify neurosarcoidosis diagnoses by their likelihood of being accurate:

… excerpt ends here. Continue reading the full article.

Illustrations

Worked examples

Example 1 — a first encounter with Neurosarcoidosis

Start with the simplest possible case. Write down what Neurosarcoidosis 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 Neurosarcoidosis 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 Neurosarcoidosis 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 Neurosarcoidosis

In research: Neurosarcoidosis 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 Neurosarcoidosis 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: Neurosarcoidosis is common in secondary-school and first-year university syllabi. It links to neighbouring topics Ailments of unknown cause, Autoimmune diseases, Neurological disorders, so understanding it makes those chapters shorter.
In everyday life: Look for Neurosarcoidosis 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 Neurosarcoidosis in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Neurosarcoidosis 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 Neurosarcoidosis out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Neurosarcoidosis in simple terms?

Why does Neurosarcoidosis 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 Neurosarcoidosis?

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 Neurosarcoidosis.