Intracranial aneurysm
This article's lead section may be too short to adequately summarize the key points. (December 2023) |
Intracranial aneurysm | |
---|---|
Other names | Cerebral aneurysm, brain aneurysm |
surgical clipping , cerebral bypass surgery, pipeline embolization |
An intracranial aneurysm, also known as a cerebral aneurysm, is a
Classification
Cerebral aneurysms are classified both by size and shape. Small aneurysms have a diameter of less than 15 mm. Larger aneurysms include those classified as large (15 to 25 mm), giant (25 to 50 mm) (0.98 inches to 1.97 inches), and super-giant (over 50 mm).[3]
Berry (saccular) aneurysms
Saccular aneurysms, also known as berry aneurysms, appear as a round outpouching and are the most common form of cerebral aneurysm.
Fusiform aneurysms
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 have an estimated annual risk of rupture between 1.6 and 1.9 percent.[6][7]
Microaneurysms
Microaneurysms, also known as
Signs and symptoms
A small, unchanging aneurysm will produce few, if any, symptoms. Before a larger aneurysm ruptures, the individual may experience such symptoms as a sudden and unusually severe headache, nausea, vision impairment, vomiting, and loss of consciousness, or no symptoms at all.[10]
Subarachnoid bleed
If an aneurysm ruptures, blood leaks into the space around the brain. This is called a subarachnoid hemorrhage. Onset is usually sudden without prodrome, classically presenting as a "thunderclap headache" worse than previous headaches.[11][12] Symptoms of a subarachnoid hemorrhage differ depending on the site and size of the aneurysm.[12] Symptoms of a ruptured aneurysm can include:[13]
- a sudden severe headache that can last from several hours to days
- nausea and vomiting
- drowsiness, confusion and/or loss of consciousness
- visual abnormalities
- meningism
- dizziness
Almost all aneurysms rupture at their apex. This leads to hemorrhage in the subarachnoid space and sometimes in brain parenchyma. Minor leakage from aneurysm may precede rupture, causing warning headaches. About 60% of patients die immediately after rupture.[14] Larger aneurysms have a greater tendency to rupture, though most ruptured aneurysms are less than 10 mm in diameter.[12]
Microaneurysms
A ruptured microaneurysm may cause an intracerebral hemorrhage, presenting as a focal neurological deficit.[12]
Rebleeding, hydrocephalus (the excessive accumulation of cerebrospinal fluid), vasospasm (spasm, or narrowing, of the blood vessels), or multiple aneurysms may also occur. The risk of rupture from a cerebral aneurysm varies according to the size of an aneurysm, with the risk rising as the aneurysm size increases.[15]
Vasospasm
Risk factors
Intracranial aneurysms may result from diseases acquired during life, or from genetic conditions. Hypertension, smoking, alcoholism, and obesity are associated with the development of brain aneurysms.[11][12][17] Cocaine use has also been associated with the development of intracranial aneurysms.[12]
Other acquired associations with intracranial aneurysms include head trauma and infections.[11]
Genetic associations
Coarctation of the aorta is also a known risk factor,[11] as is arteriovenous malformation.[14] Genetic conditions associated with connective tissue disease may also be associated with the development of aneurysms.[11] This includes:[18]
- autosomal dominant polycystic kidney disease,
- neurofibromatosis type I,
- Marfan syndrome,
- multiple endocrine neoplasia type I,
- pseudoxanthoma elasticum,
- hereditary hemorrhagic telangiectasia and
- Ehlers-Danlos syndrometypes II and IV.
Specific genes have also had reported association with the development of intracranial aneurysms, including
Pathophysiology
Both high and low wall
Generally, aneurysms larger than 7 mm in diameter should be treated because they are prone for rupture. Meanwhile, aneurysms less than 7 mm arise from the anterior and posterior communicating artery and are more easily ruptured when compared to aneurysms arising from other locations.[25]
Saccular aneurysms
Saccular aneurysms are almost always the result of hereditary weaknesses in blood vessels and typically occur within the arteries of the circle of Willis,[20][26] in order of frequency affecting the following arteries:[27]
- 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 their dilated locations (congenital), with a wall of sac made up of thickened hyalinized intima and adventitia.[14] In addition, some parts of the brain vasculature are inherently weak—particularly areas along the circle of Willis, where small communicating vessels link the main cerebral vessels. These areas are particularly susceptible to saccular aneurysms.[11] Approximately 25% of patients have multiple aneurysms, predominantly when there is a familial pattern.[12]
Diagnosis
Once suspected, intracranial aneurysms can be diagnosed radiologically using
Treatment
Emergency treatment for individuals with a ruptured cerebral aneurysm generally includes restoring deteriorating respiration and reducing intracranial pressure. Currently there are two treatment options for securing intracranial aneurysms: surgical clipping or endovascular coiling. If possible, either 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 recurrent hemorrhage.[31]
While a large
Surgical clipping
Aneurysms can be treated by clipping the base of the aneurysm with a specially-designed clip. Whilst this is typically carried out by craniotomy, a new endoscopic endonasal approach is being trialled.[38] Surgical clipping was introduced by Walter Dandy of the Johns Hopkins Hospital in 1937.[39] After clipping, a catheter angiogram or CTA can be performed to confirm complete clipping.[40]
Endovascular coiling
Endovascular coiling refers to the insertion of platinum coils into the aneurysm. 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 pushed into the aneurysm, or released into the blood stream ahead of the aneurysm. Upon depositing within the aneurysm, the coils expand and initiate a thrombotic reaction within the aneurysm. If successful, this prevents further bleeding from the aneurysm.[41] In the case of broad-based aneurysms, a stent may be passed first into the parent artery to serve as a scaffold for the coils.[42]
Cerebral bypass surgery
Cerebral bypass surgery was developed in the 1960s in Switzerland by Gazi Yaşargil. When a patient has an aneurysm involving a blood vessel or a tumor at the base of the skull wrapping around a blood vessel, surgeons eliminate the problem vessel by replacing it with an artery from another part of the body.[43]
Prognosis
Outcomes depend on the size of the aneurysm.[44] Small aneurysms (less than 7 mm) have a low risk of rupture and increase in size slowly.[44] The risk of rupture is less than one percent for aneurysms of this size.[44]
The prognosis for a ruptured cerebral aneurysm depends on the extent and location of the aneurysm, the person's age, general health, and neurological condition. Some individuals with a ruptured cerebral aneurysm die from the initial bleeding. Other individuals with cerebral aneurysm recover with little or no neurological deficit. The most significant factors in determining outcome are the Hunt and Hess grade, and age. Generally patients with Hunt and Hess grade I and II hemorrhage on admission to the emergency room and patients who are younger within the typical age range of vulnerability can anticipate a good outcome, without death or permanent disability. Older patients and those with poorer Hunt and Hess grades on admission have a poor prognosis. Generally, about two-thirds of patients have a poor outcome, death, or permanent disability.[20][45][46]
Increased availability and greater access to
Epidemiology
The prevalence of intracranial aneurysm is about 1–5% (10 million to 12 million persons in the United States) and the incidence is 1 per 10,000 persons per year in the United States (approximately 27,000), with 30- to 60-year-olds being the age group most affected.[10][20] Intracranial aneurysms occur more in women, by a ratio of 3 to 2, and are rarely seen in pediatric populations.[10][17]
See also
References
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- ^ Fusiform and dolichoectatic aneurysms By James R Brorson MD (Dr. Brorson of the University of Chicago received consultation fees from CVS-Caremark, National Peer Review Corporation, and Medico-legal Consulting.) Originally released October 28, 1997; last updated January 29, 2017; expires January 29, 2020 https://tcapp.org/wp-content/uploads/2017/09/Fusiform-and-Dolichoectatic-Aneurysms.pdf
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