An
aneurysm or
aneurism (from - aneurusma "dilation", from ἀνευρύνειν - aneurunein "to dilate") is a localized, blood-filled balloon-like
bulgeBulge may refer to:*Slang metonym for penis, referring to a visible protrusion through clothing*Hernia, sometimes referred to as a bulge or bulge out-Military:*A localized discontinuity in an extended military line...
in the wall of a
blood vesselThe blood vessels are the part of the circulatory system that transports blood throughout the body. There are three major types of blood vessels: the arteries, which carry the blood away from the heart; the capillaries, which enable the actual exchange of water and chemicals between the blood and...
. Aneurysms can commonly occur in
arteriesArteries are blood vessels that carry blood away from the heart. This blood is normally oxygenated, exceptions made for the pulmonary and umbilical arteries....
at the base of the
brainA 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 :...
(the
circle of WillisThe Circle of Willis is a circle of arteries that supply blood to the brain...
) and an
aortic aneurysmAn 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...
occurs in the main artery carrying blood from the left
ventricleVentricle may refer to:* Ventricle , the pumping chambers of the heart* Ventricular system in the brain* Ventricle of the larynx, a structure in the larynx* Stomach of the gastrointestinal tract...
of the
heartThe heart is a myogenic muscular organ found in all animals with a circulatory system , that is responsible for pumping blood throughout the blood vessels by repeated, rhythmic contractions...
. When the size of an aneurysm increases, there is a significant risk of rupture, resulting in severe hemorrhage, other complications or death. Aneurysms can be hereditary or caused by disease, both of which cause the wall of the blood vessel to weaken.
Classification
Aneurysms may be classified by type, location, and the affected vessel. Other factors may also influence the pathology and diagnosis of aneurysms.
True and false aneurysms
A true aneurysm is one that involves all three layers of the wall of an artery (intima,
mediaThe tunica media is the middle layer of an artery or vein.-Artery:It is made up of smooth muscle cells and elastic tissue...
and
adventitiaAdventitia is the outermost connective tissue covering of any organ, vessel, or other structure. It is also called the tunica adventitia or the tunica externa....
). True aneurysms include atherosclerotic, syphilitic, and congenital aneurysms, as well as
ventricular aneurysmVentricular aneurysms are one of the many complications that may occur after a heart attack . They usually arise from a patch of weakened tissue in a ventricular wall, which swells into a bubble filled with blood. This, in turn, may block the passageways leading out of the heart, leading to...
s that follow transmural
myocardial infarctionMyocardial 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...
s (aneurysms that involve all layers of the attenuated wall of the heart are also considered true aneurysms).
A
false aneurysmA pseudoaneurysm, also known as a false aneurysm, is a hematoma that forms as the result of a leaking hole in an artery. Note that the hematoma forms outside the arterial wall, so it is contained by the surrounding tissues. Also it must continue to communicate with the artery to be considered a...
or pseudo-aneurysm does not primarily involve such distortion of the vessel. It is a collection of blood leaking completely out of an artery or vein, but confined next to the vessel by the surrounding tissue. This blood-filled cavity will eventually either
thromboseA 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...
(clot) enough to seal the leak or rupture out of the tougher tissue enclosing it and flow freely between layers of other tissues or into looser tissues. Pseudoaneurysms can be caused by
traumaTrauma 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...
that punctures the artery and are a known complication of
percutaneousIn surgery, percutaneous pertains to any medical procedure where access to inner organs or other tissue is done via needle-puncture of the skin, rather than by using an "open" approach where inner organs or tissue are exposed .The percutaneous approach is commonly used in vascular procedures...
arterial procedures, such as arteriography, arterial grafting, or use of an artery for injection, such as by drug abusers unable to find a usable vein. Like true aneurysms, they may be felt as an abnormal pulsatile mass on
palpationPalpation is used as part of a physical examination in which an object is felt to determine its size, shape, firmness, or location...
.
Morphology
Aneurysms are classified by their macroscopic shape and size and are described as either saccular or fusiform. Saccular aneurysms are spherical in shape and involve only a portion of the vessel wall; they vary in size from 5 to 20 cm (8 in) in diameter, and are often filled, either partially or fully, by
thrombusA 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...
. Fusiform ("spindle-shaped") aneurysms are variable in both their diameter and length; their diameters can extend up to 20 cm (8 in). They often involve large portions of the ascending and transverse
aortic archThe arch of the aorta or the transverse aortic arch is the part of the aorta that begins at the level of the upper border of the second sternocostal articulation of the right side, and runs at first upward, backward, and to the left in front of the trachea; it is then directed backward on the left...
, the
abdominal aortaThe abdominal aorta is the largest artery in the abdominal cavity. As part of the aorta, it is a direct continuation of the descending aorta .-Path:...
, or less frequently the
iliac arteriesIn human anatomy, iliac artery refers to several anatomical structures located in the pelvis:*Common iliac artery - forms at terminus of the aorta...
. The shape of an aneurysm is not pathognomonic for a specific disease.
Location
Cerebral aneurysmA 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, also known as intracranial or brain aneurysms, occur most commonly in the
anterior cerebral artery, which is part of the
circle of WillisThe Circle of Willis is a circle of arteries that supply blood to the brain...
. The next most common sites of cerebral aneurysm occurrence are in the
internal carotid arteryIn human anatomy, the internal carotid arteries are two major arteries, one on each side of the head and neck. They arise from the common carotid arteries where these bifurcate into the internal and external carotid artery, and they supply the brain....
.
Most (94%) non-intracranial aneurysms arise distal to the origin of the
renalThe kidneys, organs with several functions, serve essential regulatory roles in most animals, including vertebrates and some invertebrates. They are essential in the urinary system and also serve homeostatic functions such as the regulation of electrolytes, maintenance of acid–base balance, and...
arteries at the infrarenal
abdominal aortaThe abdominal aorta is the largest artery in the abdominal cavity. As part of the aorta, it is a direct continuation of the descending aorta .-Path:...
, a condition mostly caused by
atherosclerosisAtherosclerosis is a condition in which an artery wall thickens as a result of the accumulation of fatty materials such as cholesterol...
.
The
thoracic aortaThe thoracic aorta is contained in the posterior mediastinal cavity.It begins at the lower border of the fourth thoracic vertebra where it is continuous with the aortic arch, and ends in front of the lower border of the twelfth thoracic vertebra, at the aortic hiatus in the diaphragm where it...
can also be involved. One common form of thoracic aortic aneurysm involves widening of the proximal aorta and the aortic root, which leads to
aortic insufficiencyAortic insufficiency , also known as aortic regurgitation , is the leaking of the aortic valve of the heart that causes blood to flow in the reverse direction during ventricular diastole, from the aorta into the left ventricle....
.
Aneurysms can also occur in the legs, particularly in the deep vessels (e.g., the
poplitealPopliteal refers to anatomical structures located in the back of the knee:*Popliteal artery*Popliteal vein*Popliteal fossa*Popliteal lymph nodes*Popliteal nerves*Popliteal pterygium...
vessels in the knee).
Arterial and venous
Arterial aneurysms are much more common, but venous aneurysms do happen (for example, the popliteal venous aneurysm).
Incidence
Incidence rates of cranial aneurysms are estimated at between 0.4% and 3.6%. Those without risk factors have expected prevalence of 2-3%. In adults, females are more likely to have aneurysms, as are those between 60 and 80. Aneurysms are rare in children.
Pediatric aneurysms
Pediatric aneurysms have different incidences and features than adult aneurysms. Intracranial aneurysms are rare in childhood, with over 95% of all aneurysms occurring in adults. Incidence rates are two to three times higher in males, while there are more large and giant aneurysms and fewer multiple aneurysms. Intracranial hemorrhages are 1.6 times more likely to be due to aneurysms than cerebral arteriovenous malformations in whites, but four times less in certain Asian populations.
Most patients, particularly infants, present with subarachnoid hemorrhage and corresponding headaches or neurological deficits. The mortality rate for pediatric aneurysms is lower than in adults.
Risk factors
Risk factors for an aneurysm include diabetes,
obesityObesity is a medical condition in which excess body fat has accumulated to the extent that it may have an adverse effect on health, leading to reduced life expectancy and/or increased health problems...
,
hypertensionHypertension 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...
, tobacco use,
alcoholismAlcoholism is a broad term for problems with alcohol, and is generally used to mean compulsive and uncontrolled consumption of alcoholic beverages, usually to the detriment of the drinker's health, personal relationships, and social standing...
, high cholesterol,
copper deficiencyCopper deficiency is a very rare hematological and neurological disorder. The neurodegenerative syndrome of copper deficiency has been recognized for some time in ruminant animals, in which it is commonly known as "swayback" The disease involves a nutritional deficiency in the trace element copper...
, and increasing age. Some types are the result of congenital, or inherited, weakness in artery walls.
Copper deficiency
A minority of aneurysms are caused by a copper deficiency. Numerous animal experiments have shown that a copper deficiency can cause diseases affected by
elastinElastin 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...
tissue strength [Harris]. The
lysyl oxidaseLysyl oxidase also known as protein-lysine 6-oxidase is a protein that, in humans, is encoded by the LOX gene. Its inhibition can cause lathyrism, but, at the same time, its upregulation by tumor cells may promote metastasis of the existing tumor, causing it to become malignant and cancerous.-...
that cross links connective tissue is secreted normally, but its activity is reduced, due to some of the initial enzyme molecules' (apo-enzyme or enzyme without the copper) lack of copper.
Aneurysms of the aorta are the chief cause of death of copper deficient chickens; depleting copper produces aneurysms in turkeys.
Men who die of aneurysms have a liver content (of copper) that can be as little as 26% of normal. In such men the median layer of the blood vessel (where the elastin is) is thinner but its elastin copper content is the same as in the elastin of normal men. The overall thickness is not different. The body must therefore have some way of preventing elastin tissue from growing if there is not enough activated lysyl oxidase for it. Men are more susceptible to aneurysms than young women, probably because
estrogenEstrogens , oestrogens , or œstrogens, are a group of compounds named for their importance in the estrous cycle of humans and other animals. They are the primary female sex hormones. Natural estrogens are steroid hormones, while some synthetic ones are non-steroidal...
increases the efficiency of absorption of copper. However, women can be affected by some of these problems after pregnancy, probably because women must give the liver of their babies copper in order for them to survive the low levels of copper in milk. A baby’s liver has up to ten times as much copper as an adult liver.
Higher alcohol content enhances copper uptake, whilst zinc, iron and copper uptake diminish with increasing sugar and alcohol contents. Handling in iron or galvanized ironware is shown to deplete copper by almost 100% of initial levels and this has potential in health risk reduction applications.
Excess intake of zinc can lead to deficiency of copper (hypocupremia). This deficiency happens because excess zinc in the body triggers reduced absorption of copper in the GI tract, resulting in increased fecal loss of copper.
Pathophysiology
The occurrence and expansion of an aneurysm in a given segment of the arterial tree involves local hemodynamic factors and factors intrinsic to the arterial segment itself.
The
aortaThe 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...
is a relatively low-resistance circuit for circulating blood. The lower extremities have higher arterial resistance, and the repeated trauma of a reflected arterial wave on the distal aorta may injure a weakened aortic wall and contribute to aneurysmal degeneration. Systemic hypertension compounds the injury, accelerates the expansion of known aneurysms, and may contribute to their formation.
Aneurysm formation is probably the result of multiple factors affecting that arterial segment and its local environment.
Many aneurysms are atherosclerotic in nature.
Increasing aneurysmal dilatation leads to increasing arterial wall tension or stress. In hemodynamic terms, the coupling of aneurysmal dilatation and increased wall stress is approximated by the law of Laplace. The Law of Laplace applied to a cylinder states that the (arterial) wall tension is equal to the pressure times the radius of the arterial conduit (T = P x R). As diameter increases, wall tension increases, which contributes to more increase in diameter and risk of rupture. Increased blood pressure (systemic hypertension) and increased aneurysm size increase arterial wall tension and therefore increase the risk of rupture.
In addition, the vessel wall is supplied by the blood within its lumen in humans (? although aorta has
Vasa vasorumThe 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....
). Therefore in a developing aneurysm, the most ischemic portion of the aneurysm is at the farthest end, resulting in weakening of the vessel wall there and aiding further expansion of the aneurysm. Thus eventually all aneurysms will, if left to complete their evolution, rupture without intervention.
A mycotic aneurysm is an aneurysm that results from an infectious process that involves the arterial wall. The attribute
mycotic is a
misnomerA misnomer is a term which suggests an interpretation that is known to be untrue. Such incorrect terms sometimes derive their names because of the form, action, or origin of the subject becoming named popularly or widely referenced—long before their true natures were known.- Sources of misnomers...
in implying a fungal cause. In fact, the main pathogens of mycotic aneurysms are gram-positive cocci.
While most aneurysms occur in an isolated form, the occurrence of berry aneurysms of the
anterior communicating arteryIn human anatomy, the anterior communicating artery is a blood vessel of the brain that connects the left and right anterior cerebral arteries....
of the
circle of WillisThe Circle of Willis is a circle of arteries that supply blood to the brain...
is associated with autosomal dominant polycystic kidney disease (ADPKD).
The third stage of
syphilisSyphilis is a sexually transmitted infection caused by the spirochete bacterium Treponema pallidum subspecies pallidum. The primary route of transmission is through sexual contact; however, it may also be transmitted from mother to fetus during pregnancy or at birth, resulting in congenital syphilis...
also manifests as aneurysm of the
aortaThe 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...
, which is due to loss of the
vasa vasorumThe 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....
in the tunica adventitia.
Symptoms and diagnosis
Diagnosis of a ruptured cerebral aneurysm is commonly made by finding signs of subarachnoid hemorrhage on a computed tomography (CT) scan. If the CT scan is negative but a ruptured aneurysm is still suspected based on clinical findings, a
lumbar punctureA lumbar puncture is a diagnostic and at times therapeutic procedure that is performed in order to collect a sample of cerebrospinal fluid for biochemical, microbiological, and cytological analysis, or very rarely as a treatment to relieve increased intracranial pressure.-Indications:The...
can be performed to detect blood in the
cerebrospinal fluidCerebrospinal fluid , Liquor cerebrospinalis, is a clear, colorless, bodily fluid, that occupies the subarachnoid space and the ventricular system around and inside the brain and spinal cord...
.
Computed tomography angiographyComputed 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:...
(CTA) is an alternative to traditional angiography and can be performed without the need for arterial catheterization. This test combines a regular CT scan with a contrast dye injected into a vein. Once the dye is injected into a vein, it travels to the cerebral arteries, and images are created using a CT scan. These images show exactly how blood flows into the brain arteries.
Cerebral Aneurysm
Symptoms for a cerebral aneurysm occur when the aneurysm pushes on a structure in the brain. In the case of a cerebral aneurysm, the symptoms for an aneurysm that has ruptured and one that has not ruptured are different.
Symptoms for an aneurysm that has not ruptured:
- Fatigue
- Loss of perception
- Loss of balance
- Speech problems
- Double vision
Symptoms for a ruptured aneurysm:
- Severe headaches
- Loss of vision
- Double vision
- Neck pain and/or stiffness
- Pain above and/or behind the eyes
- Death
Treatment
Historically, the treatment of arterial aneurysms has been limited to either surgical intervention, or
watchful waitingWatchful waiting is an approach to a medical problem in which time is allowed to pass before medical intervention or therapy is used. During this time, repeated testing may be performed....
in combination with control of
blood pressureBlood pressure is the pressure exerted by circulating blood upon the walls of blood vessels, and is one of the principal vital signs. When used without further specification, "blood pressure" usually refers to the arterial pressure of the systemic circulation. During each heartbeat, BP varies...
. In recent years, endovascular or minimally invasive techniques have been developed for many types of aneurysms.
Intracranial aneurysms
There are currently two treatment options for
brain aneurysmsA 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 :...
: surgical clipping or endovascular coiling.
Surgical clipping was introduced by
Walter DandyWalter Edward Dandy, M.D. was an American neurosurgeon and scientist. He is considered one of the founding fathers of neurosurgery, along with Victor Horsley and Harvey Cushing...
of the
Johns Hopkins HospitalThe Johns Hopkins Hospital is the teaching hospital and biomedical research facility of Johns Hopkins University School of Medicine, located in Baltimore, Maryland . It was founded using money from a bequest by philanthropist Johns Hopkins...
in 1937. It consists a
craniotomyA craniotomy is a surgical operation in which a bone flap is temporarily removed from the skull to access the brain. Craniotomies are often a critical operation performed on patients recording, brain imaging, and for neurological manipulations such as electrical stimulation and chemical...
to expose the aneurysm and closing the base of the aneurysm with a clip. The surgical technique has been modified and improved over the years. Surgical clipping remains the best method to permanently eliminate aneurysms.
Endovascular coilingEndovascular coiling, or endovascular emobilization, is a surgical treatment for cerebral aneurysms. It was developed in 1991 by Guido Guglielmi at UCLA. It is one of two surgical treatments for aneurysms, the other being surgical clipping.-Procedure:...
was introduced by Guido Guglielmi at UCLA in 1991. It consists of passing a catheter into the femoral artery in the groin, through the aorta, into the brain arteries, and finally into the aneurysm itself. Platinum coils initiate a clotting reaction within the aneurysm that, if successful, will eliminate the aneurysm.
Aortic and peripheral aneurysms
For aneurysms in the aorta, arms, legs, or head, the weakened section of the vessel may be replaced by a bypass graft that is sutured at the vascular stumps. Instead of sewing, the graft tube ends, made rigid and expandable by nitinol wireframe, can be easily inserted in its reduced diameter into the vascular stumps and then expanded up to the most appropriate diameter and permanently fixed there by external ligature.
http://www.fondazionecarrel.org/sp/sp.html New devices were recently developed to substitute the external ligature by expandable ring allowing use in acute ascending aorta dissection, providing airtight (i.e. not dependent on the coagulation integrity), easy and quick anastomosis extended to the arch concavity
http://icvts.ctsnetjournals.org/cgi/content/full/10/2/161http://www.fondazionecarrel.org/ejcts/ndaod&wikien111.html Less invasive endovascular techniques allow covered metallic stent grafts to be inserted through the arteries of the leg and deployed across the aneurysm.
See also
- Abdominal aortic aneurysm
Abdominal aortic aneurysm is a localized dilatation of the abdominal aorta exceeding the normal diameter by more than 50 percent, and is the most common form of aortic 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...
- Aortic dissection
Aortic dissection occurs when a tear in the inner wall of the aorta causes blood to flow between the layers of the wall of the aorta and force the layers apart. The dissection typically extends anterograde, but can extend retrograde from the site of the intimal tear. Aortic dissection is a medical...
- 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 :...
- Charcot-Bouchard aneurysms
- Aneurysm of sinus of Valsalva
Aneurysm of the aortic sinus, also known as the sinus of Valsalva, is comparatively rare. When present, it is usually in either the right or in the noncoronary sinus, rarely in the left Aneurysm of the aortic sinus, also known as the sinus of Valsalva, is comparatively rare. When present, it is...
- 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...
External links