2070
Intracranial aneurysm, also known as brain aneurysm.
Intracranial aneurysms are the most common cause of non-traumatic subarachnoid hemorrhage.
The formation of aneurysms is felt to be due to degeneration of internal elastic lamina, endothelial dysfunction, and hemodynamic stress, resulting in inflammation, which leads the instability of the vascular wall, which plays a crucial role in their formation and rupture.
Aneurysms, including intracranial, are classified both by size and shape.
Intracranial aneurysms may result from: diseases acquired during life, or from genetic conditions.
No specific gene loci has been identified to be associated with cerebral aneurysm.
Genes associated with the development of intracranial aneurysms: perlecan, elastin, collagen type 1 A2, endothelial nitric oxide synthase, endothelin receptor A and cyclin dependent kinase inhibitor.
Mutations in interleukin 6 may be protective.
Other genetic loci have been identified as relevant to the development of intracranial aneurysms: include genes 1, 2, 11, and 19.
Additional risk factors that contributes to the formation of aneurysm are: cigarette smoking, hypertension, female gender, alcoholism, family history of cerebral aneurysm, infection, and head trauma.
Cocaine use may be associated with the development of intracranial aneurysms.
Genetic associations with intracranial aneurysms:
Coarctation of the aorta is also a known risk factor.
Arteriovenous malformations
Connective tissue diseases
Autosomal dominant polycystic kidney disease.
Neurofibromatosis type I
Marfan syndrome
Multiple endocrine neoplasia type I
Pseudoxanthoma elasticum
Hereditary hemorrhagic telangiectasia.
Ehlers-Danlos syndrome types II and IV
Small aneurysms have a diameter of less than 15 mm.
Larger aneurysms include those classified as large (15 to 25 mm), and giant (25 to 50 mm), and super-giant (over 50 mm).
Studies have identified single nucleotide polymorphisms CDK2NB, EDNRA, and SOX 17 genes as major contributors to intracranial aneurysm formation.
Family history of intracranial, aneurysms, or subarachnoid hemorrhage increases the risk of unruptured intracranial aneurysms that are more likely to have subarachnoid hemorrhage at smaller aneurysm size and younger ages, and with worse outcomes in persons with sporadic intracranial aneurysms.
For intracranial aneurysms larger than 7 mm in diameter treatment should be initiated because they are prone for rupture.
Aneurysms less than 7 mm, however, arising from anterior and posterior communicating artery are more easily ruptured when compared to aneurysms arising from other locations.
Saccular aneurysms, are known as berry aneurysms.
Berry aneurysms appear as a round outpouching and are the most common form of cerebral aneurysm.
Charcot-Bouchard aneurysms are a common cause of intracranial hemorrhage.
Charcot-Bouchard aneurysms or aneurysms of the brain vasculature which occur in small blood vessels less than 300 mm in diameter.
Charcot-Bouchard aneurysms are most often located in the lenticulostriate vessels of the basal ganglia and are associated with chronic hypertension.
A small, unchanging aneurysm will produce few, if any, symptoms.
Fusiform (dolichoectatic) aneurysms represent a widening of a segment of an artery around the entire blood vessel, rather than just arising from a side of an artery’s wall.
They usually do not rupture.
Unruptured intracranial aneurysms are usually asymptomatic and often diagnosed incidentally through imaging.
Symptomatic aneurysms can cause cranial nerve palsies, seizures, facial pain, hemiparesis, ischemia, visual disturbances, and symptoms may arise with compression or thromboembolism and vary related to location.
The prevalence of intracranial aneurysm is about 1-5% or 10 million to 12 million persons in the United States.
In a systemic review of 94,912 patients from 21 countries the overall prevalence of unruptured intracranial aneurysms was estimated at 3.2% among persons without coexisting medical conditions with an average age of 50 years.
A high prevalence is observed among women, persons 30 years of age or older, and those with a family history of unruptured intracranial, aneurysms, subarachnoid hemorrhage, hypertension, or autosomal, dominant polycystic disease (Vlak MH).
The incidence of intracranial aneurysm is 1 per 10,000 persons per year in the United States, or approximately 27,000, with 30- to 60-year-olds being the age group most affected.
Intracranial aneurysms occur more in women, by a ratio of 3 to 2.
2-3% of the general population.
20-25% of patients have a misdiagnosis or delay in diagnosis of aneurysm at initial presentation.
Symptoms range from: None, severe headache, visual problems, nausea, vomiting, and confusion.
headaches are common and in patients with unruptured intracranial aneurysms, but are often not directly related to the aneurysm.
Almost all intracranial aneurysms rupture at their apex, with hemorrhage into the subarachnoid space and sometimes the brain parenchyma.
Larger aneurysms have a greater tendency to rupture.
The risk of a subarachnoid hemorrhage is greater with a saccular aneurysm than a fusiform aneurysm.
Saccular aneurysms are almost always the result of hereditary weakness in blood vessels.
Saccular aneurysms account for approximately 90% of lesions and typically form at arterial bifurcations in the internal carotid artery, the anterior and posterior communicating arteries, and the middle cerebral artery.
In the posterior circulation, they commonly occur in the basilar artery bifurcation and cerebellar artery branch points.
Less common types of unruptured intracranial aneurysms include fusiform aneurysms involving a long segments of the artery, mycotic aneurysms associated with infections, and dissecting aneurysms resulting from arterial injury.
Up to 20% of patients with unruptured intracranial aneurysms have multiple intracranial aneurysms.
Saccular aneurysms typically occur within the arteries of the Circle of Willis: affecting the following arteries in order of frequency
Anterior communicating artery
Posterior communicating artery
Middle cerebral artery
Internal carotid artery
Tip of basilar artery
Saccular aneurysms tend to have a lack of tunica media and elastic lamina around its dilated location.
The wall of sac made up of thickened hyalinized intima and adventitia.
Parts of the brain vasculature are inherently weak, especially the Circle of Willis, where small communicating vessels link the main cerebral vessels.
At these areas there is particularly susceptibility to saccular aneurysms.
A ruptured microaneurysm may cause an intracerebral hemorrhage, with focal neurological findings.
Minor leakage from aneurysm may cause warning headaches.
After intracranial aneurysm rupture, about 60% of patients die.
Most ruptured aneurysms are less than 10 mm in diameter.
Before rupture, a large aneurysm may be asymptomatic or associated with symptoms: sudden and unusually severe headache, nausea, vision impairment, vomiting, and loss of consciousness, or the individual may experience no symptoms at all.
When an intracranial aneurysm ruptures, blood leaks into the space around the brain, a subarachnoid hemorrhage.
Subarachnoid hemorrhage is associated with high mortality, making early detection and measures to reduce the risk of unruptured intracranial aneurysm formation, a major strategy.
The risk of intracranial aneurysm rupture is influenced by the aneurysm size, location, morphologic features, and patient specific factors such as hypertension, smoking, and family history.
Aneurysm rupture onset is usually sudden without prodrome, presenting as a severe headache worse than previous headaches.
Symptoms of a subarachnoid hemorrhage differ depending on the site and size of the aneurysm.
Symptoms of a ruptured aneurysm include:
a sudden severe headache that can last from several hours to days
nausea and vomiting
drowsiness, confusion and/or loss of consciousness
visual abnormalities
meningismus
Usual onset 30-60 years old.
Causes: Hypertension, infection, head trauma.
Risk factors: Smoking, old age, family history, cocaine use.
Risk factors for unruptured intracranial aneurysms are classified as modifiable and nonmodifiable.
Modifiable risk factors include cigarette, smoking, and hypertension.
Nonmodifiable risk factors for unruptured intracranial aneurysm formation include female sex, increasing age, and genetic predisposition.
The risk of unruptured intracranial aneurysm is higher among women, especially older than 50 years of age than among men with a female to male risk ratio of two to one.
Approximately 25% of patients have multiple intracranial aneurysms, predominantly when there is familial pattern.
7% of unruptured aneurysms less than 1 cm present with aneurysmal symptoms other than rupture.
Most common cause of the non traumatic subarachnoid hemorrhage.
Commonly undetected until manifestations of subarachnoid hemorrhage, intracerebral hemorrhage or both.
Incidence of aneurysmal subarachnoid hemorrhage estimated between 16 and 30,000 per year.
Short term mortality after a subarachnoid hemorrhage can be as high as 45%.
Most deaths from aneurysmal subarachnoid hemorrhage can be due to initial hemorrhage, rebleeding, vasospasm of cerebral vessels or major medical complications.
Subarachnoid hemorrhage from intracranial aneurysms rupture is a severe and life-threatening condition associated with early death and loss of productive life years and a case fatality rate ranging from 8.3 to 66.7%.
Subarachnoid hemorrhage affects a young and predominantly female population, and amongst survivors few of them, 1/3 have full recovery and a substantial proportion indoor long-term effects that lead to dependent living.
Anemia occurs in more than 50% of patients with subarachnoid hemorrhage and is associated with worse clinical outcomes.
In patients with aneurysmal subarachnoid hemorrhage, and anemia, a liberal transfusion strategy does not result in a lower risk of unfavorable neurological outcomes at one year, than a restrictive strategy.
Intracranial aneurysms may rebleed.
Intracranial aneurysms may lead to hydrocephalus, or vasospasm.
Vasospasm of blood vessels can occur secondary to subarachnoid hemorrhage following a ruptured aneurysm.
Vasospasm is most likely to occur within 21 days of an intracranial aneurysm rupture, and is seen radiologically within 60% of such patients.
The associated vasospasm is thought to be related to apoptosis of inflammatory cells such as macrophages and neutrophils that become trapped in the subarachnoid space.
These cells reach the subarachnoid space to phagocytose the hemorrhaged red blood cells.
With apoptosis, there is a degranulation of vasoconstrictors, including endothelins and free radicals, that cause the vasospasm.
13.5%-60% of major aneurysm ruptures associated with unrecognized warning signs.
The annual risk of rupture is as low as .05% for small anterior circulation aneurysms of less than 10 mm in patients without previous subarachnoid hemorrhage, the annual risk of rupture was 1% for aneurysms 10 mm or larger and as high as 6% for aneurysms 25 mm or larger.
In patients with previous subarachnoid hemorrhage, there are higher annual risks of rupture of approximately .5%
With subarachnoid hemorrhage affects 28,000 people per year and is associated with death or permanent disability in nearly two thirds of patients.
Most recent studies suggesting 2-4% of general population has an unruptured intracranial aneurysm.
Increasing incidence with advancing age.
Intracranial aneurysms are rarely seen in pediatric populations.
Manifests as a weakness in the wall of a cerebral artery or vein causes a localized dilation or ballooning of the blood vessel.
The repeated trauma of blood flow against the vessel wall presses against the point of weakness and causes the aneurysm to enlarge.
It is theorized low shear stress causes growth and rupture of large aneurysms through inflammatory response while high shear stress causes growth and rupture of small aneurysm through response from the blood vessel wall.
This causes fibrosis of the arterial wall, with reduction of number of smooth muscle cells, abnormal collagen synthesis, resulting in thinning of arterial wall and formation of aneurysm and rupture.
Primary goal in management involves the detection and treatment before catastrophic rupture.
Treatment options for intracranial aneurysm:
For asymptomatic patients with small, less than 7 mm, incidental unruptured intracranial aneurysms should be treated conservatively because of their low risk of rupture, with a focus on modifiable factors associated with aneurysm growth.
Such factors include smoking sensation, and blood pressure control.
routine noninvasive CTA and MRA monitoring every six months until stable then annually is recommended for conservative therapy.
Aneurysm showing growth of at least 0.5 mm over 36 months on follow up imaging May prompt closer monitoring.
Endovascular coiling, Surgical clipping, Cerebral bypass surgery.
MRI angiography and CT tomographic angiography are preferred for the detection of intracranial aneurysms, with digital subtraction angiography reserved for complex cases or treatment planning.
Digital subtraction angiography provides superior detail of aneurysmal features, detects, very small aneurysms, and facilitates pre-treatment planning.
Cerebral angiography is the standard technique to diagnose and characterize the anatomy of a cerebral aneurysm and imaging is utilized in planning medical, endovascular, or surgical treatment.
Incidence of subarachnoid hemorrhage from intracranial aneurysm increases with age.
80-90% of all intracranial aneurysms are saccular or berry aneurysms, which appear as small, round berrylike dilatations.
Aneurysms in the posterior circulation involving the basilar artery, vertebral arteries and posterior communicating artery,have a higher risk of rupture.
Basilar artery aneurysms represent only 3-5% of all intracranial aneurysm.
Basilar artery aneurysms, however, are the most common aneurysms in the posterior circulation.
Multiple aneurysms occur in 20-25% of patients with saccular aneurysms and approximately 20% of patients have a family history of subarachnoid hemorrhages or intracranial aneurysms.
Associated with polycystic kidney, arteriovenous malformations, aortic coarctation, Marfan’s syndrome, Ehlers-Danlos syndrome, pseudoxanthoma elasticum, fibromuscular dysplasia, and pituitary tumors.
Wide variability in growth rate of aneurysms from hours, weeks to several years.
Some aneurysms may decrease in size or spontaneous obliterate.
A large percentage of unruptured intracranial aneurysms appear to remain unchanged in size over time.
Intracranial aneurysms can be diagnosed radiologically using magnetic resonance or CT angiography.
Computed tomographic angiography or MR angiography are preferred for routine screening of high risk patients because of their sensitivity and non-invasive nature.
Such methods have limited sensitivity for diagnosis of small aneurysms.
Lumbar puncture (LP) is the gold standard technique for determining aneurysm rupture with a subarachnoid hemorrhage.
CSF is analyzed for RBC count, and presence or absence of xanthochromia.
Diagnosis by Angiography, CT scan.
Angiographic diagnosis and treatment with coil embolization can be performed during the diagnostic procedure.
Rupture during diagnostic angiogram is extraordinarily rare.
Treatment for a ruptured cerebral aneurysm generally includes restoring deteriorating respiration and reducing intracranial pressure.
The two treatment options for securing intracranial aneurysms: surgical clipping or endovascular coiling.
Endovascular techniques for intracranial aneurysm treatment include coil embolization, which involves introducing platinum coils into the aneurysm, sac, scaffolding techniques to prevent coil prolapse by infiltrating a balloon in the parent artery or deploying stent across the aneurysm neck, flow diversion, which involves the placement of flow diverter devices into the parent artery to divert blood flow away from the aneurysm sac and flow disruption which involves placement of an intrasaccular device within the aneurysm sac to disrupt blood flow from the aneurysm
Surgical clipping or endovascular coiling is typically performed within the first 24 hours after bleeding to occlude the ruptured aneurysm and reduce the risk of rebleeding.
Surgical clipping is a traditional treatment for unruptured intracerebral aneurysms, and involves placing microsurgical clips across the neck of the aneurysm through a craniotomy and micro surgery.
Clipping is more effective than endovascular treatment for aneurysm occlusion, but is associated with longer hospitalizations and higher incidence of neurological deficits.
Surgical clipping is typically preferred for younger patients with smaller aneurysms of less than 10 mm, in the anterior circulation.
For complex intracranial aneurysms, particularly arising from small distal vessels, or in cases in which endovascular techniques are not feasible or have failed cerebral vascular bypass surgery remains an effective treatment option.
Meta-analysis found the outcomes and risks of surgical clipping and endovascular coiling to be statistically similar.
The International Subarachnoid Aneurysm Trial indicated a higher rate of recurrence when intracerebral aneurysms are treated using endovascular coiling.
Endovascular coiling consists of the insertion of platinum coils into the aneurysm.
With endovascular coiling a catheter is inserted into a blood vessel, typically the femoral artery, and passed through blood vessels into the cerebral circulation and the aneurysm.
Coils are released into the blood stream ahead of the aneurysm.
Coils expand and initiate a thrombotic reaction within the aneurysm.
Coiling prevents further bleeding from the aneurysm.
Aneurysms can be clipped at the base of the aneurysm by craniotomy, or by endoscopic endonasal approach.
Cerebral bypass surgery may be used when a patient has an aneurysm involving a blood vessel at the base of the skull by replacing it with an artery from another part of the body.
Small aneurysms of less than 7 mm have a low risk of rupture of less than one percent for aneurysms of this size.
The prognosis for a ruptured cerebral aneurysm varies with the extent and location of the aneurysm.
Other prognostic factors include age, general health, and neurological condition of the patient.
A initial ruptured cerebral aneurysm may be lethal.
In others with cerebral aneurysm rupture recovery with little or no neurological deficit can occur.
The most important factors in determining prognosis of a cerebral aneurysm rupture are age and the
Hunt and Hess scale.
Patients with Hunt and Hess grade I and II hemorrhage, and patients who are younger can anticipate a good outcome, without death or permanent disability.
Older patients and those with poorer Hunt and Hess grades have a poor prognosis.
Generally, about two-thirds of patients with an intracranial aneurysm rupture have a poor outcome, death, or permanent disability
Conservative management focuses on smoking cessation, blood pressure control, and routine imaging follow up.
Intervention management with endovascular or surgical treatment is reserved for higher risk aneurysms at 7 mm or greater in diameter and located in the anterior circulation.
Endovascular techniques, including coiling and flow diversion have a lower preoperative risk, but higher risk of recurrence, whereas surgical clipping provides durable results, but with greater procedural risks.
During endovascular treatment intraprocedural aneurysm rupture can occur in as many as 8% of cases and if occurs, carries mortality rate of up to 38%.
Endovascular treatment complications are associated to guide wire perforation, microcatheter perforation or coil perforation, and less commonly to increased intraaneurysmal pressure induced by injection of contrast medium.