biology

Vertebral artery dissection

Vertebral artery dissection 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 Vertebral artery dissection rather than just read about it. In short: Vertebral artery dissection (VAD) is a flap-like tear of the inner lining of the vertebral artery, which is located in the neck and supplies blood to the brain. After the tear, blood enters the arterial wall and forms a blood clot, thickening the artery wall and often impeding blood flow.

Key takeaways

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

Reference excerpt

Vertebral artery dissection (VAD) is a flap-like tear of the inner lining of the vertebral artery, which is located in the neck and supplies blood to the brain. After the tear, blood enters the arterial wall and forms a blood clot, thickening the artery wall and often impeding blood flow. The symptoms of vertebral artery dissection include head and neck pain and intermittent or permanent stroke symptoms such as difficulty speaking, impaired coordination, and visual loss. It is usually diagnosed with a contrast-enhanced CT or MRI scan. Vertebral dissection may occur after physical trauma to the neck, such as a blunt injury (e.g. traffic collision) or strangulation, or after sudden neck movements (e.g. coughing), but may also happen spontaneously. 1–4% of spontaneous cases have a clear underlying connective tissue disorder affecting the blood vessels. Treatment is usually with either antiplatelet drugs such as aspirin or with anticoagulants such as heparin or warfarin. Vertebral artery dissection is less common than carotid artery dissection (dissection of the large arteries in the front of the neck). The two conditions together account for 10–25% of non-hemorrhagic strokes in young and middle-aged people. Over 75% recover completely or with minimal impact on functioning, with the remainder having more severe disability and a very small proportion (about 2%) dying from complications. It was first described in the 1970s by the Canadian neurologist C. Miller Fisher.

Classification Vertebral artery dissection is one of the two types of cervical artery dissection. The other type, carotid artery dissection, involves the carotid arteries. Vertebral artery dissection is further classified as being either traumatic (caused by mechanical trauma to the neck) or spontaneous, and it may also be classified by the part of the artery involved: extracranial (the part outside the skull) and intracranial (the part inside the skull).

Signs and symptoms Head pain occurs in 50–75% of all cases of vertebral artery dissection. It tends to be located at the back of the head, either on the affected side or in the middle, and develops gradually. It is either dull or pressure-like in character or throbbing. About half of those with VAD consider the headache distinct, while the remainder have had a similar headache before. It is suspected that VAD with headache as the only symptom is fairly common; 8% of all cases of vertebral and carotid dissection are diagnosed on the basis of pain alone. Obstruction of blood flow through the affected vessel may lead to dysfunction of part of the brain supplied by the artery. This happens in 77–96% of cases. This may be temporary ("transient ischemic attack") in 10–16% of cases, but many (67–85% of cases) end up with a permanent deficit or a stroke. The vertebral artery supplies the part of the brain that lies in the posterior fossa of the skull, and this type of stroke is therefore called a posterior circulation infarct. Problems may include difficulty speaking or swallowing (lateral medullary syndrome); this occurs in less than a fifth of cases and occurs due to dysfunction of the brainstem. Others may experience unsteadiness or lack of coordination due to involvement of the cerebellum, and still others may develop visual loss (on one side of the visual field) due to involvement of the visual cortex in the occipital lobe. In the event of involvement of the sympathetic tracts in the brainstem, a partial Horner's syndrome may develop; this is the combination of a drooping eyelid, constricted pupil, and an apparently sunken eye on one side of the face. If the dissection of the artery extends to the part of the artery that lies inside the skull, subarachnoid hemorrhage may occur (1% of cases). This arises due to rupture of the artery and accumulation of blood in the subarachnoid space. It may be characterized by a different, usually severe headache; it may also cause a range of additional neurological symptoms. 13–16% of all people with vertebral or carotid dissection have dissection in another cervical artery. It is therefore possible for the symptoms to occur on both sides, or for symptoms of carotid artery dissection to occur at the same time as those of vertebral artery dissection. Some give a figure of multiple vessel dissection as high as 30%.

Causes The causes of vertebral artery dissection can be grouped under two main categories, spontaneous and traumatic.

Spontaneous Spontaneous cases are considered to be caused by intrinsic factors that weaken the arterial wall. Only a very small proportion (1–4%) have a clear underlying connective tissue disorder, such as Ehlers–Danlos syndrome type 4 and, more rarely, Marfan syndrome. However, ultrastructural abnormalities of the dermal connective tissue components are discernible in two out of three patients with spontaneous dissection. Ehlers–Danlos syndrome type 4, caused by mutations of the COL3A gene, leads to defective production of the collagen, type III, alpha 1 protein and causes skin fragility as well as weakness of the walls of arteries and internal organs. Marfan syndrome results from mutations in the FBN1 gene, defective production of the protein fibrillin-1, and a number of physical abnormalities including aneurysm of the aortic root. There have also been reports in other genetic conditions, such as osteogenesis imperfecta type 1, autosomal dominant polycystic kidney disease and pseudoxanthoma elasticum, α1 antitrypsin deficiency and hereditary hemochromatosis, but evidence for these associations is weaker. Genetic studies in other connective tissue-related genes have mostly yielded negative results. Other abnormalities to the blood vessels, such as fibromuscular dysplasia, have been reported in a proportion of cases. Atherosclerosis does not appear to increase the risk. There have been numerous reports of associated risk factors for vertebral artery dissection; many of these reports suffer from methodological weaknesses, such as selection bias. Elevated homocysteine levels, often due to mutations in the MTHFR gene, appear to increase the risk of vertebral artery dissection. People with an aneurysm of the aortic root and people with a history of migraine may be predisposed to vertebral artery dissection. Vascular tortuosity or redundancy in young patients is associated with an increased risk of spontaneous dissection.

… excerpt ends here. Continue reading the full article.

Illustrations

Vertebral artery dissection: A reconstruction of the vertebral arteries from a CT scan, seen from the front. From the bottom, V1 is from the subclavian artery to the foramina, V2 is from the foramina to the second vertebra, V3 is between the foramina until entry into the skull, and V4 is inside the skull embedded in the dura mater. They merge into the basilar artery, which then divides into the posterior cerebral artery. — A reconstruction of the vertebral arteries from a CT scan, seen from the front. From the bottom, V1 is from the subclavian artery to the foramina, V2 is from the foramina to the second vertebra, V3 is between the foramina until entry into the skull, and V4 is inside the skull embedded in the dura mater. They merge into the basilar artery, which then divides into the posterior cerebral artery.

Worked examples

Example 1 — a first encounter with Vertebral artery dissection

Start with the simplest possible case. Write down what Vertebral artery dissection 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 Vertebral artery dissection 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 Vertebral artery dissection 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 Vertebral artery dissection

In research: Vertebral artery dissection 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 Vertebral artery dissection 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: Vertebral artery dissection is common in secondary-school and first-year university syllabi. It links to neighbouring topics Neurological disorders, Vascular diseases, so understanding it makes those chapters shorter.
In everyday life: Look for Vertebral artery dissection 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 Vertebral artery dissection in 20 minutes

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

Frequently asked questions

What is Vertebral artery dissection in simple terms?

Why does Vertebral artery dissection 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 Vertebral artery dissection?

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 Vertebral artery dissection.