Vertebral artery dissection
Encyclopedia
Vertebral artery dissection (abbreviated VAD, often vertebral dissection) is a dissection
(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, direct blow to the neck), strangulation or manipulation
, 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 drug
s such as aspirin
or with anticoagulant
s 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 combined 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 Miller Fisher
.
. 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).
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%.
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. Presence of an aneurysm
of the aortic root and a history of migraine
may predispose to vertebral artery dissection.
s associated with cough
ing. It has been difficult to prove the association with mild trauma and infections statistically. It is likely that many "spontaneous" cases may in fact have been caused by such relatively minor insults in someone predisposed by other structural problems to the vessels.
Vertebral artery dissection has also been reported in association with chiropractic
and other forms of neck manipulation. In hospital-based studies this was the underlying cause for 16–28% of cases, but it has been suggested that the true figure may be higher and that there is significant under-reporting. Reports of the association are of weak to moderately strong quality, and many of the reports have methodological flaws. It has been suggested that the relationship is causative, but this is disputed by proponents of these treatment modalities, who believe that the dissection is probably already present before people seek treatment.
, and for much of their tract run through the transverse foramen
of the lowest five of the six vertebrae of the neck
. After exiting at the level of the first cervical vertebra, its course changes from vertical to horizontal, and then enters the skull
through the foramen magnum. Inside the skull, the arteries merge to form the basilar artery
, which joins the circle of Willis
. In total, three quarters of the artery are outside the skull; it has a high mobility in this area due to rotational movement in the neck and is therefore vulnerable to trauma. Most dissections happen at the level of the first and second vertebrae. The vertebral artery supplies a number of vital structures in the posterior cranial fossa
, such as the brainstem, the cerebellum
and the occipital lobe
s. The brainstem harbors a number of vital functions (such as respiration
) and controls the nerves of the face and neck. The cerebellum is part of the diffuse system that coordinates movement. Finally, the occipital lobes participate in the sense of vision.
Dissection occurs when blood accumulates in the wall of the blood vessel. This is most likely due to a tear in the tunica intima
(the inner layer), allowing blood to enter the tunica media
, although other lines of evidence have suggested that the blood may instead arise from the vasa vasorum
, the small blood vessels that supply the outer layer of larger blood vessels. Various theories exist as to whether people who sustain carotid and vertebral artery dissection, even if not suffering from a connective tissue disorder, have an underlying vulnerability. Biopsy samples of skin and other arteries has indicated that this might be a possibility, but no genetic defect in collagen
or elastin
genes has been convincingly proven. Other studies have indicated inflammation
of the blood vessels, as measured by highly sensitive C-reactive protein
(hsCRP, a marker of inflammation) in the blood.
Once dissection has occurred, two mechanisms contribute to the development of stroke symptoms. Firstly, the flow through the blood vessel may be disrupted due to the accumulation of blood under the vessel wall, leading to ischemia
(insufficient blood supply). Secondly, irregularities in the vessel wall and turbulence increase the risk of thrombosis
(the formation of blood clots) and embolism
(migration) of these clots of the brain. From various lines of evidence, it appears that thrombosis and embolism is the predominant problem.
Subarachnoid hemorrage due to arterial rupture typically occurs if the dissection extends into the V4 section of the artery. This may be explained by the fact that the arterial wall is thinner and lacks a number of structural supports in this section.
is cerebral angiography
(with or without digital subtraction angiography
). This involves puncture of a large artery (usually the femoral artery
) and advancing an intravascular catheter through the aorta
towards the vertebral arteries. At that point, radiocontrast
is injected and its downstream flow captured on fluoroscopy
(continuous X-ray imaging). The vessel may appear stenotic
(narrowed, 41–75%), occluded (blocked, 18–49%), or as an aneurysm
(area of dilation, 5–13%). The narrowing may be described as "rat's tail" or "string sign". Cerebral angiography is an invasive procedure
, and it requires large volumes of radiocontrast that can cause complications such as kidney damage
. Angiography also does not directly demonstrate the blood in the vessel wall, as opposed to more modern modalities. The only remaining use of angiography is when endovascular treatment is contemplated (see below).
More modern methods involve computed tomography (CT angiography
) and magnetic resonance imaging
(MR angiography
). They use smaller amounts of contrast and are not invasive. CT angiography and MR angiography are more or less equivalent when used to diagnose or exclude vertebral artery dissection. CTA has the advantage of showing certain abnormalities earlier, tends to be available outside office hours, and can be performed rapidly. When MR angiography is used, the best results are achieved in the T1
setting using a protocol known as "fat suppression". Doppler ultrasound is less useful as it provides little information about the part of the artery close to the skull base and in the vertebral foramina, and any abnormality detected on ultrasound would still require confirmation with CT or MRI.
and warfarin
) and antiplatelet drug
s (usually aspirin
). More rarely, thrombolysis
(medication that dissolves blood clots) may be administered, and occasionally obstruction may be treated with angioplasty
and stent
ing. No randomized controlled trial
s have been performed to compare the different treatment modalities. Surgery
is only used in exceptional cases.
From analysis of the existing small treatment trials of cervical artery dissection (carotid and vertebral) it appears that aspirin
and anticoagulation (heparin
followed by warfarin
) are equally effective in reducing the risk of further stroke or death. Anticoagulation is regarded as more powerful than antiplatelet therapy, but anticoagulants may increase the size of the hematoma and worsening obstruction of the affected artery. Anticoagulation may be relatively unsafe if a large stroke has already occurred, as hemorrhagic transformation is relatively common, and if the dissection extends into V4 (carrying a risk of subarachnoid hemorrhage). Anticoagulation may be appropriate if there is rapid blood flow (through a severely narrowed vessel) on transcranial doppler
despite the use of aspirin, if there is a completely occluded vessel, if there are recurrent stroke-like episodes, or if free-floating blood clot is visible on scans. Warfarin is typically continued for 3–6 months, as during this time the flow through the artery usually improves, and most strokes happen within the first 6 months after the development of the dissection. Some regard 3 months as sufficient.
Professional guidelines in the UK recommend that patients with VA dissection should be enrolled in a clinical trial
comparing aspirin and anticoagulation if possible. American guidelines state that the benefit of anticoagulation is not currently established.
Thrombolysis is enzymatic destruction of blood clots. This is achieved by the administration of a drug (such as urokinase
or alteplase) that activates plasmin
, an enzyme that occurs naturally in the body and digests clots
when activated. Thrombolysis is an accepted treatment for heart attacks
and stroke unrelated to dissection. In cervical artery dissection, only small case series are available. The thrombolytic drug is administered either intravenously
or during cerebral angiography through a catheter directly into the affected artery. The data indicates that thrombolysis is safe, but its place in the treatment of VAD is uncertain.
Stenting involves the catheterization of the affected artery during angiography, and the insertion of a mesh-like tube; this is known as "endovascular therapy
" (inside the blood vessel). This may be performed to allow the blood to flow through a severely narrowed vessel, or to seal off an aneurysm. However, it is unclear whether the technical success of the procedure translates into improved outcomes, as in both cases the problem often resolves spontaneously over time. Stenting, as well as the insertion of coils
by means of angiography, may be performed if there is an aneurysm and/or extension of the dissection into the V4 section of the artery.
Surgery carries a high risk of complications, and is typically only offered in case of inexorable deterioration or contraindications to any of the other treatments. Various arterial repair procedures have been described.
of 0–2) is generally about 75%, or possibly slightly better (85.7%) if antiplatelet drugs are used. In studies of anticoagulants and aspirin, the combined mortality with either treatment is 1.8-2.1%.
After the initial episode, 2% may experience a further episode within the first month. After this, there is a 1% annual risk of recurrence. Those with high blood pressure
and dissections in multiple arteries may have a higher risk of recurrence. Further episodes of cervical artery dissection are more common in those who are younger, have a family history of cervical artery dissection, or have a diagnosis of Ehlers-Danlos syndrome or fibromuscular dysplasia.
and France
. From 1994 to 2003, the incidence increased threefold; this has been attributed to the more widespread use of modern imaging modalities rather than a true increase. Similarly, those living in urban areas are more likely to receive appropriate investigations, accounting for increased rates of diagnosis in those dwelling in cities. It is suspected that a proportion of cases in people with mild symptoms remains undiagnosed.
There is controversy as to whether VAD is more common in men or in women; an aggregate of all studies shows that it is slightly higher incidence in men (56% versus 44%). Men are on average 37–44 years old at diagnosis, and women 34–44. While dissection of the carotid and vertebral arteries accounts for only 2% of strokes (which are usually caused by high blood pressure
and other risk factors, and tend to occur in the elderly), they cause 10–25% of strokes in young and middle-aged people.
Dissecting aneurysms of the vertebral artery constitute 4% of all cerebral aneurysm
s, and are hence a relatively rare but important cause of subarachnoid hemorrhage.
, a Canadian neurologist
and stroke physician working at Massachusetts General Hospital
, first noted the "string sign" abnormality in carotid arteries on cerebral angiograms of stroke patients, and subsequently discovered that the same abnormality could occur in the vertebral arteries. He reported the discovery in a paper in 1978.
Dissection (medical)
In medical pathology, dissection refers to a tear within the wall of a blood vessel, which allows blood to separate the wall layers, creating a pseudoaneurysm.- Types :Examples include:*Aortic dissection...
(a flap-like tear) of the inner lining of the vertebral artery
Vertebral artery
The vertebral arteries are major arteries of the neck. They branch from the subclavian arteries and merge to form the single midline basilar artery in a complex called the vertebrobasilar system, which supplies blood to the posterior part of the circle of Willis and thus significant portions of the...
, which is located in the neck and supplies blood to the brain
Brain
The brain is the center of the nervous system in all vertebrate and most invertebrate animals—only a few primitive invertebrates such as sponges, jellyfish, sea squirts and starfishes do not have one. It is located in the head, usually close to primary sensory apparatus such as vision, hearing,...
. After the tear, blood enters the arterial wall and forms a blood clot
Thrombus
A thrombus , or blood clot, is the final product of the blood coagulation step in hemostasis. It is achieved via the aggregation of platelets that form a platelet plug, and the activation of the humoral coagulation system...
, 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
Stroke
A stroke, previously known medically as a cerebrovascular accident , is the rapidly developing loss of brain function due to disturbance in the blood supply to the brain. This can be due to ischemia caused by blockage , or a hemorrhage...
symptoms such as difficulty speaking
Dysarthria
Dysarthria is a motor speech disorder resulting from neurological injury of the motor component of the motor-speech system and is characterized by poor articulation of phonemes...
, impaired coordination
Ataxia
Ataxia is a neurological sign and symptom that consists of gross lack of coordination of muscle movements. Ataxia is a non-specific clinical manifestation implying dysfunction of the parts of the nervous system that coordinate movement, such as the cerebellum...
and visual loss. It is usually diagnosed with a contrast-enhanced CT or MRI
Magnetic resonance imaging
Magnetic resonance imaging , nuclear magnetic resonance imaging , or magnetic resonance tomography is a medical imaging technique used in radiology to visualize detailed internal structures...
scan.
Vertebral dissection may occur after physical trauma
Physical trauma
Trauma refers to "a body wound or shock produced by sudden physical injury, as from violence or accident." It can also be described as "a physical wound or injury, such as a fracture or blow." Major trauma can result in secondary complications such as circulatory shock, respiratory failure and death...
to the neck, such as a blunt injury (e.g. traffic collision, direct blow to the neck), strangulation or manipulation
Spinal manipulation
Spinal manipulation is a therapeutic intervention performed on spinal articulations which are synovial joints . These articulations in the spine that are amenable to spinal manipulative therapy include the z-joints, the atlanto-occipital, atlanto-axial, lumbosacral, sacroiliac, costotransverse...
, 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 drug
Antiplatelet drug
An antiplatelet drug is a member of a class of pharmaceuticals that decrease platelet aggregation and inhibit thrombus formation...
s such as aspirin
Aspirin
Aspirin , also known as acetylsalicylic acid , is a salicylate drug, often used as an analgesic to relieve minor aches and pains, as an antipyretic to reduce fever, and as an anti-inflammatory medication. It was discovered by Arthur Eichengrun, a chemist with the German company Bayer...
or with anticoagulant
Anticoagulant
An anticoagulant is a substance that prevents coagulation of blood. A group of pharmaceuticals called anticoagulants can be used in vivo as a medication for thrombotic disorders. Some anticoagulants are used in medical equipment, such as test tubes, blood transfusion bags, and renal dialysis...
s such as heparin
Heparin
Heparin , also known as unfractionated heparin, a highly sulfated glycosaminoglycan, is widely used as an injectable anticoagulant, and has the highest negative charge density of any known biological molecule...
or warfarin
Warfarin
Warfarin is an anticoagulant. It is most likely to be the drug popularly referred to as a "blood thinner," yet this is a misnomer, since it does not affect the thickness or viscosity of blood...
.
Vertebral artery dissection is less common than carotid artery dissection
Carotid artery dissection
Carotid artery dissection is a separation of the layers of the artery wall supplying oxygen-bearing blood to the head and brain, and is the most common cause of stroke in young adults...
(dissection of the large arteries in the front of the neck). The two conditions combined 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 Miller Fisher
Miller Fisher
Charles Miller Fisher, usually known as Miller Fisher is a neurologist. Trained in Canada, he spent 1949 at Massachusetts General Hospital, followed by several years in Montreal. In 1954 he returned to Massachusetts General on the stroke service, beginning a long career in stroke neurology...
.
Classification
Vertebral artery dissection is one of the two types of dissection of the arteries in the neck. The other type, carotid artery dissection, involves the carotid arteriesCarotid artery
Carotid artery can refer to:* Common carotid artery* External carotid artery* Internal carotid artery...
. 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 painHeadache
A headache or cephalalgia is pain anywhere in the region of the head or neck. It can be a symptom of a number of different conditions of the head and neck. The brain tissue itself is not sensitive to pain because it lacks pain receptors. Rather, the pain is caused by disturbance of the...
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
Transient ischemic attack
A transient ischemic attack is a transient episode of neurologic dysfunction caused by ischemia – either focal brain, spinal cord or retinal – without acute infarction...
") 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
Posterior cranial fossa
The posterior cranial fossa is part of the intracranial cavity, located between the foramen magnum and tentorium cerebelli. It contains the brainstem and cerebellum.This is the most inferior of the fossae. It houses the cerebellum, medulla and pons....
of the skull, and this type of stroke is therefore called a posterior circulation infarct
Posterior circulation infarct
A Posterior Circulation Infarct is a type of cerebral infarction affecting the posterior circulation supplying one side of the brain....
. Problems may include difficulty speaking or swallowing (lateral medullary syndrome
Lateral medullary syndrome
Lateral medullary syndrome is a disease in which the patient has a constellation of neurologic symptoms due to injury to the lateral part of the medulla in the brain, resulting in tissue ischemia and necrosis.-Signs and symptoms:This syndrome is characterized by sensory deficits affecting...
); 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
Ataxia
Ataxia is a neurological sign and symptom that consists of gross lack of coordination of muscle movements. Ataxia is a non-specific clinical manifestation implying dysfunction of the parts of the nervous system that coordinate movement, such as the cerebellum...
due to involvement of the cerebellum
Cerebellum
The cerebellum is a region of the brain that plays an important role in motor control. It may also be involved in some cognitive functions such as attention and language, and in regulating fear and pleasure responses, but its movement-related functions are the most solidly established...
, and still others may develop visual loss (on one side of the visual field
Homonymous hemianopsia
Hemianopsia or hemianopia is visual field loss that respects the vertical midline, and usually affects both eyes, but can involve one eye only. Homonymous hemianopsia, or homonymous hemianopia occurs when there is hemianopic visual field loss on the same side of both eyes...
) due to involvement of the visual cortex
Visual cortex
The visual cortex of the brain is the part of the cerebral cortex responsible for processing visual information. It is located in the occipital lobe, in the back of the brain....
in the occipital lobe
Occipital lobe
The occipital lobe is the visual processing center of the mammalian brain containing most of the anatomical region of the visual cortex. The primary visual cortex is Brodmann area 17, commonly called V1...
. In the event of involvement of the sympathetic tracts
Sympathetic nervous system
The sympathetic nervous system is one of the three parts of the autonomic nervous system, along with the enteric and parasympathetic systems. Its general action is to mobilize the body's nervous system fight-or-flight response...
in the brainstem, a partial Horner's syndrome
Horner's syndrome
Horner's syndrome is the combination of drooping of the eyelid and constriction of the pupil , sometimes accompanied by decreased sweating of the face on the same side; redness of the conjunctiva of the eye is often also present...
may develop; this is the combination of a drooping eyelid
Ptosis (eyelid)
Ptosis is a drooping of the upper or lower eyelid. The drooping may be worse after being awake longer, when the individual's muscles are tired. This condition is sometimes called "lazy eye", but that term normally refers to amblyopia...
, constricted pupil
Miosis
Miosis is the constriction of the pupil of the eye to two millimeters or less...
, and an apparently sunken eye
Enophthalmos
Enophthalmos is the recession of the eyeball within the orbit.It may be a congenital anomaly, or be acquired as a result of trauma , Horner's syndrome, silent sinus syndrome, or phthisis bulbi....
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
Subarachnoid hemorrhage
A subarachnoid hemorrhage , or subarachnoid haemorrhage in British English, is bleeding into the subarachnoid space—the area between the arachnoid membrane and the pia mater surrounding the brain...
may occur (1% of cases). This arises due to rupture of the artery and accumulation of blood in the subarachnoid space
Subarachnoid space
In the central nervous system, the subarachnoid cavity is the interval between the arachnoid membrane and pia mater....
. 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's syndrome. 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's syndrome results from mutations in the FBN1FBN1
Fibrillin-1 is a protein that in humans is encoded by the FBN1 gene.This gene encodes a member of the fibrillin family. The encoded protein is a large, extracellular matrix glycoprotein that serve as a structural component of 10-12 nm calcium-binding microfibrils...
gene, defective production of the protein fibrillin-1, and a number of physical abnormalities including aneurysm of the aortic root
Thoracic aortic aneurysm
A thoracic aortic aneurysm is an aortic aneurysm that presents primarily in the thorax.It is less common than an abdominal aortic aneurysm. However, a syphilitic aneurysm is more likely to be a thoracic aortic aneurysm than an abdominal aortic aneurysm....
.
There have also been reports in other genetic conditions, such as osteogenesis imperfecta type 1
Osteogenesis imperfecta
Osteogenesis imperfecta is a genetic bone disorder. People with OI are born with defective connective tissue, or without the ability to make it, usually because of a deficiency of Type-I collagen...
, autosomal dominant polycystic kidney disease
Polycystic kidney disease
Autosomal dominant polycystic kidney disease is an inherited systemic disorder that predominantly affects the kidneys, but may affect other organs including the liver, pancreas, brain, and arterial blood vessels...
and pseudoxanthoma elasticum
Pseudoxanthoma elasticum
Pseudoxanthoma elasticum , also known as Grönblad–Strandberg syndrome, is a genetic disease that causes fragmentation and mineralization of elastic fibers in some tissues. The most common problems arise in the skin and eyes, and later in blood vessels in the form of premature atherosclerosis...
, α1 antitrypsin deficiency
Alpha 1-antitrypsin deficiency
Alpha 1-antitrypsin deficiency is an autosomal recessive genetic disorder caused by defective production of alpha 1-antitrypsin , leading to decreased A1AT activity in the blood and lungs, and deposition of excessive abnormal A1AT protein in liver cells...
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
Fibromuscular dysplasia
Fibromuscular dysplasia, or fibromuscular dysplasia of arteries, often abbreviated as FMD, is a disease that can cause narrowing of arteries in the kidneys, the carotid arteries supplying the brain, and, less commonly, the arteries of the abdomen...
, have been reported in a proportion of cases. Atherosclerosis
Atherosclerosis
Atherosclerosis is a condition in which an artery wall thickens as a result of the accumulation of fatty materials such as cholesterol...
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
Scientific method
Scientific method refers to a body of techniques for investigating phenomena, acquiring new knowledge, or correcting and integrating previous knowledge. To be termed scientific, a method of inquiry must be based on gathering empirical and measurable evidence subject to specific principles of...
weaknesses, such as selection bias
Selection bias
Selection bias is a statistical bias in which there is an error in choosing the individuals or groups to take part in a scientific study. It is sometimes referred to as the selection effect. The term "selection bias" most often refers to the distortion of a statistical analysis, resulting from the...
. Elevated homocysteine
Homocysteine
Homocysteine is a non-protein amino acid with the formula HSCH2CH2CHCO2H. It is a homologue of the amino acid cysteine, differing by an additional methylene group. It is biosynthesized from methionine by the removal of its terminal Cε methyl group...
levels, often due to mutations in the MTHFR
Methylenetetrahydrofolate reductase
Methylenetetrahydrofolate reductase is an enzyme that in humans is encoded by the MTHFR gene. Methylenetetrahydrofolate reductase catalyzes the conversion of 5,10-methylenetetrahydrofolate to 5-methyltetrahydrofolate, a cosubstrate for homocysteine remethylation to methionine...
gene, appear to increase the risk of vertebral artery dissection. Presence of an aneurysm
Aortic aneurysm
An aortic aneurysm is a general term for any swelling of the aorta to greater than 1.5 times normal, usually representing an underlying weakness in the wall of the aorta at that location...
of the aortic root and a history of migraine
Migraine
Migraine is a chronic neurological disorder characterized by moderate to severe headaches, and nausea...
may predispose to vertebral artery dissection.
Traumatic
Traumatic vertebral dissection may follow blunt trauma to the neck, such as in a traffic collision, direct blow to the neck, or strangulation. 1–2% of those with major trauma may have an injury to the carotid or vertebral arteries. In many cases of vertebral dissection, people report recent very mild trauma to the neck or sudden neck movements, e.g. in the context of playing sports. Others report a recent infection, particularly respiratory tract infectionRespiratory tract infection
Respiratory tract infection refers to any of a number of infectious diseases involving the respiratory tract. An infection of this type is normally further classified as an upper respiratory tract infection or a lower respiratory tract infection...
s associated with cough
Cough
A cough is a sudden and often repetitively occurring reflex which helps to clear the large breathing passages from secretions, irritants, foreign particles and microbes...
ing. It has been difficult to prove the association with mild trauma and infections statistically. It is likely that many "spontaneous" cases may in fact have been caused by such relatively minor insults in someone predisposed by other structural problems to the vessels.
Vertebral artery dissection has also been reported in association with chiropractic
Chiropractic
Chiropractic is a health care profession concerned with the diagnosis, treatment and prevention of disorders of the neuromusculoskeletal system and the effects of these disorders on general health. It is generally categorized as complementary and alternative medicine...
and other forms of neck manipulation. In hospital-based studies this was the underlying cause for 16–28% of cases, but it has been suggested that the true figure may be higher and that there is significant under-reporting. Reports of the association are of weak to moderately strong quality, and many of the reports have methodological flaws. It has been suggested that the relationship is causative, but this is disputed by proponents of these treatment modalities, who believe that the dissection is probably already present before people seek treatment.
Mechanism
The vertebral arteries arise from the subclavian arterySubclavian artery
In human anatomy, the subclavian arteries are two major arteries of the upper thorax , below the clavicle . They receive blood from the top of the aorta...
, and for much of their tract run through the transverse foramen
Transverse foramen
The transverse foramen pierces the transverse processes of the seven cervical vertebrae. In the upper six vertebrae, the foramen gives passage to the vertebral artery, vertebral vein, and a plexus of sympathetic nerves. The seventh foramen lacks the artery, but contains the vein and sympathetic...
of the lowest five of the six vertebrae of the neck
Cervical vertebrae
In vertebrates, cervical vertebrae are those vertebrae immediately inferior to the skull.Thoracic vertebrae in all mammalian species are defined as those vertebrae that also carry a pair of ribs, and lie caudal to the cervical vertebrae. Further caudally follow the lumbar vertebrae, which also...
. After exiting at the level of the first cervical vertebra, its course changes from vertical to horizontal, and then enters the skull
Skull
The skull is a bony structure in the head of many animals that supports the structures of the face and forms a cavity for the brain.The skull is composed of two parts: the cranium and the mandible. A skull without a mandible is only a cranium. Animals that have skulls are called craniates...
through the foramen magnum. Inside the skull, the arteries merge to form the basilar artery
Basilar artery
In human anatomy, the basilar artery is one of the arteries that supplies the brain with oxygen-rich blood.The two vertebral arteries and the basilar artery are sometimes together called the vertebrobasilar system, which supplies blood to the posterior part of circle of Willis and anastomoses with...
, which joins the circle of Willis
Circle of Willis
The Circle of Willis is a circle of arteries that supply blood to the brain...
. In total, three quarters of the artery are outside the skull; it has a high mobility in this area due to rotational movement in the neck and is therefore vulnerable to trauma. Most dissections happen at the level of the first and second vertebrae. The vertebral artery supplies a number of vital structures in the posterior cranial fossa
Posterior cranial fossa
The posterior cranial fossa is part of the intracranial cavity, located between the foramen magnum and tentorium cerebelli. It contains the brainstem and cerebellum.This is the most inferior of the fossae. It houses the cerebellum, medulla and pons....
, such as the brainstem, the cerebellum
Cerebellum
The cerebellum is a region of the brain that plays an important role in motor control. It may also be involved in some cognitive functions such as attention and language, and in regulating fear and pleasure responses, but its movement-related functions are the most solidly established...
and the occipital lobe
Occipital lobe
The occipital lobe is the visual processing center of the mammalian brain containing most of the anatomical region of the visual cortex. The primary visual cortex is Brodmann area 17, commonly called V1...
s. The brainstem harbors a number of vital functions (such as respiration
Respiration (physiology)
'In physiology, respiration is defined as the transport of oxygen from the outside air to the cells within tissues, and the transport of carbon dioxide in the opposite direction...
) and controls the nerves of the face and neck. The cerebellum is part of the diffuse system that coordinates movement. Finally, the occipital lobes participate in the sense of vision.
Dissection occurs when blood accumulates in the wall of the blood vessel. This is most likely due to a tear in the tunica intima
Tunica intima
The tunica intima is the innermost layer of an artery or vein. It is made up of one layer of endothelial cells and is supported by an internal elastic lamina...
(the inner layer), allowing blood to enter the tunica media
Tunica media
The tunica media is the middle layer of an artery or vein.-Artery:It is made up of smooth muscle cells and elastic tissue...
, although other lines of evidence have suggested that the blood may instead arise from the vasa vasorum
Vasa vasorum
The vasa vasorum is a network of small blood vessels that supply large blood vessels.The vasa vasorum are found in large arteries and veins such as the aorta and its branches....
, the small blood vessels that supply the outer layer of larger blood vessels. Various theories exist as to whether people who sustain carotid and vertebral artery dissection, even if not suffering from a connective tissue disorder, have an underlying vulnerability. Biopsy samples of skin and other arteries has indicated that this might be a possibility, but no genetic defect in collagen
Collagen
Collagen is a group of naturally occurring proteins found in animals, especially in the flesh and connective tissues of mammals. It is the main component of connective tissue, and is the most abundant protein in mammals, making up about 25% to 35% of the whole-body protein content...
or elastin
Elastin
Elastin is a protein in connective tissue that is elastic and allows many tissues in the body to resume their shape after stretching or contracting. Elastin helps skin to return to its original position when it is poked or pinched. Elastin is also an important load-bearing tissue in the bodies of...
genes has been convincingly proven. Other studies have indicated inflammation
Inflammation
Inflammation is part of the complex biological response of vascular tissues to harmful stimuli, such as pathogens, damaged cells, or irritants. Inflammation is a protective attempt by the organism to remove the injurious stimuli and to initiate the healing process...
of the blood vessels, as measured by highly sensitive C-reactive protein
C-reactive protein
C-reactive protein is a protein found in the blood, the levels of which rise in response to inflammation...
(hsCRP, a marker of inflammation) in the blood.
Once dissection has occurred, two mechanisms contribute to the development of stroke symptoms. Firstly, the flow through the blood vessel may be disrupted due to the accumulation of blood under the vessel wall, leading to ischemia
Ischemia
In medicine, ischemia is a restriction in blood supply, generally due to factors in the blood vessels, with resultant damage or dysfunction of tissue. It may also be spelled ischaemia or ischæmia...
(insufficient blood supply). Secondly, irregularities in the vessel wall and turbulence increase the risk of thrombosis
Thrombosis
Thrombosis is the formation of a blood clot inside a blood vessel, obstructing the flow of blood through the circulatory system. When a blood vessel is injured, the body uses platelets and fibrin to form a blood clot to prevent blood loss...
(the formation of blood clots) and embolism
Embolism
In medicine, an embolism is the event of lodging of an embolus into a narrow capillary vessel of an arterial bed which causes a blockage in a distant part of the body.Embolization is...
(migration) of these clots of the brain. From various lines of evidence, it appears that thrombosis and embolism is the predominant problem.
Subarachnoid hemorrage due to arterial rupture typically occurs if the dissection extends into the V4 section of the artery. This may be explained by the fact that the arterial wall is thinner and lacks a number of structural supports in this section.
Diagnosis
Various diagnostic modalities exist to demonstrate blood flow or absence thereof in the vertebral arteries. The gold standardGold standard (test)
In medicine and statistics, gold standard test refers to a diagnostic test or benchmark that is the best available under reasonable conditions. It does not have to be necessarily the best possible test for the condition in absolute terms...
is cerebral angiography
Cerebral angiography
Cerebral angiography is a form of angiography which provides images of blood vessels in and around the brain, thereby allowing detection of abnormalities such as arteriovenous malformations and aneurysms....
(with or without digital subtraction angiography
Digital subtraction angiography
Digital subtraction angiography is a type of fluoroscopy technique used in interventional radiology to clearly visualize blood vessels in a bony or dense soft tissue environment. Images are produced using contrast medium by subtracting a 'pre-contrast image' or the mask from later images, once...
). This involves puncture of a large artery (usually the femoral artery
Femoral artery
The femoral artery is a general term comprising a few large arteries in the thigh. They begin at the inguinal ligament and end just above the knee at adductor canal or Hunter's canal traversing the extent of the femur bone....
) and advancing an intravascular catheter through the aorta
Aorta
The aorta is the largest artery in the body, originating from the left ventricle of the heart and extending down to the abdomen, where it branches off into two smaller arteries...
towards the vertebral arteries. At that point, radiocontrast
Radiocontrast
Radiocontrast agents are a type of medical contrast medium used to improve the visibility of internal bodily structures in an X-ray based imaging techniques such as computed tomography or radiography...
is injected and its downstream flow captured on fluoroscopy
Fluoroscopy
Fluoroscopy is an imaging technique commonly used by physicians to obtain real-time moving images of the internal structures of a patient through the use of a fluoroscope. In its simplest form, a fluoroscope consists of an X-ray source and fluorescent screen between which a patient is placed...
(continuous X-ray imaging). The vessel may appear stenotic
Stenosis
A stenosis is an abnormal narrowing in a blood vessel or other tubular organ or structure.It is also sometimes called a stricture ....
(narrowed, 41–75%), occluded (blocked, 18–49%), or as an aneurysm
Aneurysm
An aneurysm or aneurism is a localized, blood-filled balloon-like bulge in the wall of a blood vessel. Aneurysms can commonly occur in arteries at the base of the brain and an aortic aneurysm occurs in the main artery carrying blood from the left ventricle of the heart...
(area of dilation, 5–13%). The narrowing may be described as "rat's tail" or "string sign". Cerebral angiography is an invasive procedure
Invasiveness of surgical procedures
There are three main categories which describe the invasiveness of surgical procedures. These are: non-invasive procedures, minimally invasive procedures, and invasive procedures ....
, and it requires large volumes of radiocontrast that can cause complications such as kidney damage
Contrast-induced nephropathy
Contrast-induced nephropathy is defined as either a greater than 25% increase of serum creatinine or an absolute increase in serum creatinine of 0.5 mg/dL after a radiographic examination using a contrast agent....
. Angiography also does not directly demonstrate the blood in the vessel wall, as opposed to more modern modalities. The only remaining use of angiography is when endovascular treatment is contemplated (see below).
More modern methods involve computed tomography (CT angiography
Computed tomography angiography
Computed tomography angiography is a computed tomography technique used to visualize arterial and venous vessels throughout the body. This ranges from arteries serving the brain to those bringing blood to the lungs, kidneys, arms and legs.-Technique:...
) and magnetic resonance imaging
Magnetic resonance imaging
Magnetic resonance imaging , nuclear magnetic resonance imaging , or magnetic resonance tomography is a medical imaging technique used in radiology to visualize detailed internal structures...
(MR angiography
Magnetic Resonance Angiography
Magnetic resonance angiography is a group of techniques based on Magnetic Resonance Imaging to image blood vessels. Magnetic resonance angiography is used to generate images of the arteries in order to evaluate them for stenosis , occlusion or aneurysms...
). They use smaller amounts of contrast and are not invasive. CT angiography and MR angiography are more or less equivalent when used to diagnose or exclude vertebral artery dissection. CTA has the advantage of showing certain abnormalities earlier, tends to be available outside office hours, and can be performed rapidly. When MR angiography is used, the best results are achieved in the T1
Spin-lattice relaxation time
Spin–lattice relaxation is the mechanism by which the z component of the magnetization vector comes into thermodynamic equilibrium with its surroundings in nuclear magnetic resonance and magnetic resonance imaging. It is characterized by the spin–lattice relaxation time, a time constant known as T1...
setting using a protocol known as "fat suppression". Doppler ultrasound is less useful as it provides little information about the part of the artery close to the skull base and in the vertebral foramina, and any abnormality detected on ultrasound would still require confirmation with CT or MRI.
Treatment
Treatment is focused on reducing stroke episodes and damage from a distending artery. Four treatment modalities have been reported in the treatment of vertebral artery dissection. The two main treatments involve medication: anticoagulation (using heparinHeparin
Heparin , also known as unfractionated heparin, a highly sulfated glycosaminoglycan, is widely used as an injectable anticoagulant, and has the highest negative charge density of any known biological molecule...
and warfarin
Warfarin
Warfarin is an anticoagulant. It is most likely to be the drug popularly referred to as a "blood thinner," yet this is a misnomer, since it does not affect the thickness or viscosity of blood...
) and antiplatelet drug
Antiplatelet drug
An antiplatelet drug is a member of a class of pharmaceuticals that decrease platelet aggregation and inhibit thrombus formation...
s (usually aspirin
Aspirin
Aspirin , also known as acetylsalicylic acid , is a salicylate drug, often used as an analgesic to relieve minor aches and pains, as an antipyretic to reduce fever, and as an anti-inflammatory medication. It was discovered by Arthur Eichengrun, a chemist with the German company Bayer...
). More rarely, thrombolysis
Thrombolysis
Thrombolysis is the breakdown of blood clots by pharmacological means. It is colloquially referred to as clot busting for this reason...
(medication that dissolves blood clots) may be administered, and occasionally obstruction may be treated with angioplasty
Angioplasty
Angioplasty is the technique of mechanically widening a narrowed or obstructed blood vessel, the latter typically being a result of atherosclerosis. An empty and collapsed balloon on a guide wire, known as a balloon catheter, is passed into the narrowed locations and then inflated to a fixed size...
and stent
Stent
In the technical vocabulary of medicine, a stent is an artificial 'tube' inserted into a natural passage/conduit in the body to prevent, or counteract, a disease-induced, localized flow constriction. The term may also refer to a tube used to temporarily hold such a natural conduit open to allow...
ing. No randomized controlled trial
Randomized controlled trial
A randomized controlled trial is a type of scientific experiment - a form of clinical trial - most commonly used in testing the safety and efficacy or effectiveness of healthcare services or health technologies A randomized controlled trial (RCT) is a type of scientific experiment - a form of...
s have been performed to compare the different treatment modalities. Surgery
Surgery
Surgery is an ancient medical specialty that uses operative manual and instrumental techniques on a patient to investigate and/or treat a pathological condition such as disease or injury, or to help improve bodily function or appearance.An act of performing surgery may be called a surgical...
is only used in exceptional cases.
Anticoagulation and aspirin
Aspirin
Aspirin , also known as acetylsalicylic acid , is a salicylate drug, often used as an analgesic to relieve minor aches and pains, as an antipyretic to reduce fever, and as an anti-inflammatory medication. It was discovered by Arthur Eichengrun, a chemist with the German company Bayer...
and anticoagulation (heparin
Heparin
Heparin , also known as unfractionated heparin, a highly sulfated glycosaminoglycan, is widely used as an injectable anticoagulant, and has the highest negative charge density of any known biological molecule...
followed by warfarin
Warfarin
Warfarin is an anticoagulant. It is most likely to be the drug popularly referred to as a "blood thinner," yet this is a misnomer, since it does not affect the thickness or viscosity of blood...
) are equally effective in reducing the risk of further stroke or death. Anticoagulation is regarded as more powerful than antiplatelet therapy, but anticoagulants may increase the size of the hematoma and worsening obstruction of the affected artery. Anticoagulation may be relatively unsafe if a large stroke has already occurred, as hemorrhagic transformation is relatively common, and if the dissection extends into V4 (carrying a risk of subarachnoid hemorrhage). Anticoagulation may be appropriate if there is rapid blood flow (through a severely narrowed vessel) on transcranial doppler
Transcranial doppler
Transcranial Doppler is a test that measures the velocity of blood flow through the brain's blood vessels. Used to help in the diagnosis of emboli, stenosis, vasospasm from a subarachnoid hemorrhage , and other problems, this relatively quick and inexpensive test is growing in popularity in the...
despite the use of aspirin, if there is a completely occluded vessel, if there are recurrent stroke-like episodes, or if free-floating blood clot is visible on scans. Warfarin is typically continued for 3–6 months, as during this time the flow through the artery usually improves, and most strokes happen within the first 6 months after the development of the dissection. Some regard 3 months as sufficient.
Professional guidelines in the UK recommend that patients with VA dissection should be enrolled in a clinical trial
Clinical trial
Clinical trials are a set of procedures in medical research and drug development that are conducted to allow safety and efficacy data to be collected for health interventions...
comparing aspirin and anticoagulation if possible. American guidelines state that the benefit of anticoagulation is not currently established.
Thrombolysis, stenting and surgery
Thrombolysis, stenting and surgery are not used as widely as anticoagulation or antiplatelet drugs. These treatments are invasive or more risky, and are typically reserved for situations where symptoms worsen despite medical treatment, or where medical treatment may be unsafe (e.g. an unacceptable bleeding tendency).Thrombolysis is enzymatic destruction of blood clots. This is achieved by the administration of a drug (such as urokinase
Urokinase
Urokinase , also called urokinase-type plasminogen activator , is a serine protease . Urokinase was originally isolated from human urine, but is present in several physiological locations, such as blood stream and the extracellular matrix...
or alteplase) that activates plasmin
Plasmin
Plasmin is an important enzyme present in blood that degrades many blood plasma proteins, most notably, fibrin clots. The degradation of fibrin is termed fibrinolysis. In humans, the plasmin protein is encoded by the PLG gene.- Function :...
, an enzyme that occurs naturally in the body and digests clots
Fibrinolysis
Fibrinolysis is a process that prevents blood clots from growing and becoming problematic. This process has two types: primary fibrinolysis and secondary fibrinolysis...
when activated. Thrombolysis is an accepted treatment for heart attacks
Myocardial infarction
Myocardial infarction or acute myocardial infarction , commonly known as a heart attack, results from the interruption of blood supply to a part of the heart, causing heart cells to die...
and stroke unrelated to dissection. In cervical artery dissection, only small case series are available. The thrombolytic drug is administered either intravenously
Intravenous therapy
Intravenous therapy or IV therapy is the infusion of liquid substances directly into a vein. The word intravenous simply means "within a vein". Therapies administered intravenously are often called specialty pharmaceuticals...
or during cerebral angiography through a catheter directly into the affected artery. The data indicates that thrombolysis is safe, but its place in the treatment of VAD is uncertain.
Stenting involves the catheterization of the affected artery during angiography, and the insertion of a mesh-like tube; this is known as "endovascular therapy
Endovascular surgery
Endovascular surgery is a form of minimally invasive surgery that was designed to access many regions of the body via major blood vessels.Endovascular techniques were originally designed for diagnostic purposes. Basic techniques involve the introduction of a catheter percutaneously into a large...
" (inside the blood vessel). This may be performed to allow the blood to flow through a severely narrowed vessel, or to seal off an aneurysm. However, it is unclear whether the technical success of the procedure translates into improved outcomes, as in both cases the problem often resolves spontaneously over time. Stenting, as well as the insertion of coils
Guglielmi Detachable Coil
A Guglielmi Detachable Coil, or GDC, is a platinum coil commonly used in intracranial non-invasive surgery for the occlusion of brain aneurysms. It was invented by Italian interventional neuroradiologist Dr...
by means of angiography, may be performed if there is an aneurysm and/or extension of the dissection into the V4 section of the artery.
Surgery carries a high risk of complications, and is typically only offered in case of inexorable deterioration or contraindications to any of the other treatments. Various arterial repair procedures have been described.
Prognosis
Prognosis of spontaneous cervical arterial dissection involves neurological and arterial results. The overall functional prognosis of individuals with stroke due to cervical artery dissection does not appear to vary from that of young people with stroke due to other causes. The rate of survival with good outcome (a modified Rankin scoreModified Rankin Scale
The modified Rankin Scale is a commonly used scale for measuring the degree of disability or dependence in the daily activities of people who have suffered a stroke, and it has become the most widely used clinical outcome measure for stroke clinical trials. It was originally introduced in 1957 by...
of 0–2) is generally about 75%, or possibly slightly better (85.7%) if antiplatelet drugs are used. In studies of anticoagulants and aspirin, the combined mortality with either treatment is 1.8-2.1%.
After the initial episode, 2% may experience a further episode within the first month. After this, there is a 1% annual risk of recurrence. Those with high blood pressure
Hypertension
Hypertension or high blood pressure is a cardiac chronic medical condition in which the systemic arterial blood pressure is elevated. What that means is that the heart is having to work harder than it should to pump the blood around the body. Blood pressure involves two measurements, systolic and...
and dissections in multiple arteries may have a higher risk of recurrence. Further episodes of cervical artery dissection are more common in those who are younger, have a family history of cervical artery dissection, or have a diagnosis of Ehlers-Danlos syndrome or fibromuscular dysplasia.
Epidemiology
The annual incidence is about 1.1 per 100,000 annually in population studies from the United StatesUnited States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
and France
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...
. From 1994 to 2003, the incidence increased threefold; this has been attributed to the more widespread use of modern imaging modalities rather than a true increase. Similarly, those living in urban areas are more likely to receive appropriate investigations, accounting for increased rates of diagnosis in those dwelling in cities. It is suspected that a proportion of cases in people with mild symptoms remains undiagnosed.
There is controversy as to whether VAD is more common in men or in women; an aggregate of all studies shows that it is slightly higher incidence in men (56% versus 44%). Men are on average 37–44 years old at diagnosis, and women 34–44. While dissection of the carotid and vertebral arteries accounts for only 2% of strokes (which are usually caused by high blood pressure
Hypertension
Hypertension or high blood pressure is a cardiac chronic medical condition in which the systemic arterial blood pressure is elevated. What that means is that the heart is having to work harder than it should to pump the blood around the body. Blood pressure involves two measurements, systolic and...
and other risk factors, and tend to occur in the elderly), they cause 10–25% of strokes in young and middle-aged people.
Dissecting aneurysms of the vertebral artery constitute 4% of all cerebral aneurysm
Cerebral aneurysm
A cerebral or brain aneurysm is a cerebrovascular disorder in which weakness in the wall of a cerebral artery or vein causes a localized dilation or ballooning of the blood vessel.- Signs and symptoms :...
s, and are hence a relatively rare but important cause of subarachnoid hemorrhage.
History
Spontaneous vertebral artery dissection was described in the 1970s. Prior to this, there had been isolated case reports about carotid dissection. In 1971, C. Miller FisherMiller Fisher
Charles Miller Fisher, usually known as Miller Fisher is a neurologist. Trained in Canada, he spent 1949 at Massachusetts General Hospital, followed by several years in Montreal. In 1954 he returned to Massachusetts General on the stroke service, beginning a long career in stroke neurology...
, a Canadian neurologist
Neurology
Neurology is a medical specialty dealing with disorders of the nervous system. Specifically, it deals with the diagnosis and treatment of all categories of disease involving the central, peripheral, and autonomic nervous systems, including their coverings, blood vessels, and all effector tissue,...
and stroke physician working at Massachusetts General Hospital
Massachusetts General Hospital
Massachusetts General Hospital is a teaching hospital and biomedical research facility in the West End neighborhood of Boston, Massachusetts...
, first noted the "string sign" abnormality in carotid arteries on cerebral angiograms of stroke patients, and subsequently discovered that the same abnormality could occur in the vertebral arteries. He reported the discovery in a paper in 1978.
External links
- Cervical Artery Dissections and Ischemic Stroke Patients, international research collaboration into cervical artery dissection