Intracranial berry aneurysm
||It has been suggested that this article be merged into Cerebral aneurysm. (Discuss) Proposed since February 2013.|
|Intracranial berry aneurysm|
|Classification and external resources|
The most common sites of intracranial saccular aneurysms.
An intracranial berry aneurysm, also known as a saccular aneurysm, is a sac-like outpouching in a cerebral blood vessel, which can seem berry-shaped, hence the name. Once a berry aneurysm has formed it is likely to rupture, causing a stroke. Thus they are serious medical emergencies, and should be treated as soon as possible.
The risk factors for developing berry aneurysms include any condition that causes hypertension, or any condition that causes weakening of blood vessel walls,1 such as smoking, alcohol abuse,2 and cocaine use.3 Conditions that cause weakening of blood vessel walls include genetic or acquired malformation of a blood vessel, genetic disorders of connective tissue, head trauma, and infections. Coarctation of aorta is also a risk factor.1 Vestigial remnants of embryological arteries usually cause aneurysms away from bifurcations.4
Berry aneurysms are usually found in the region of the Circle of Willis.5 Berry aneurysms are congenital in nature and result in a weakness of the blood vessel wall. Weak or thinned parts of the cerebral vasculature usually consist of fibrous tissue only.6 These are vulnerable to the increased hydrostatic pressure caused by hypertension, and will bulge out. Berry aneurysms tend to have a lack of tunica media and elastic lamina around its dilated location (congenital), with wall of sac made up of thickened hyalinized intima and adventitia.4 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 berry aneurysms.1 Approximately 25% patients have multiple aneurysms, predominantly when there is familial pattern.3
These aneurysms can form in both the anterior circulation and the posterior circulation in the brain, especially at sites of bifurcation of vessels. In order of frequency, berry aneurysms arise from these places in circle of willis:7
- Posterior communicating artery
- Anterior communicating artery
- Middle cerebral artery
- Internal carotid artery
- Tip of basilar artery
Almost all aneurysms rupture at apex. This leads to hemorrhage in 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.4 Larger aneurysms have greater tendency to rupture, though most of ruptured aneurysms are less than 10 mm in diameter.3
The typical symptom of a ruptured berry aneurysm is the development of a headache so bad that the patient may say "it is the worst headache I have ever had",1 classically known as "thunderclap headache".3
Most intracranial berry aneurysms do not show any symptoms unless they have ruptured, which causes bleeding in the brain. Small aneurysms that maintain their size generally will not show symptoms. But larger aneurysms that are steadily growing can put pressure on nerves and tissues. Signs of an aneurysm that has not ruptured include (but are not limited to):
- Double vision (Diplopia)
- Loss of vision
- Eye pain
- Stiff neck (Meningismus)
- Sentinel or warning headaches. These are headaches that are caused by leakage of blood into the brain for days up to weeks prior to the aneurysm's rupture (only a small percentage of patients experience a sentinel headache before rupture).
- Loss of consciousness
General symptoms of ruptured aneurysm are:
- Sudden, severe headache: Like a rail road spike being hammered into your skull
- Confusion and/or stupor
- Sudden mood swings (Impulsivity, Irritability, Poor temper control)
- Speech impediment (dysarthria)
- Eyelids dropping, especially unilaterally (Ptosis)
- Movement disorders (ataxia), especially unilaterally.
Symptoms of a ruptured aneurysm depending on site of aneurysm in brain:6
If the aneurysm is in carotid territories, the symptoms are:
If the aneurysm is in cavernous sinus, the symptoms are:
- frontal headache
- orbital headache, pulsating exophthalmos, retinal hemorrhage, occlusion of central retinal vein, and hemorrhagic edema of eyelid
- Oculomotor nerve palsy
- Sixth nerve palsy
- Horner syndrome
- Sensory deficit over are supplied by V1 and V2 divisions of Trigeminal nerve
If the aneurysms is in vertebrobasilar territories, the symptoms are:
- Trigeminal nerve deficit
- Acoustic nerve deficit
- Lower cranial nerve deficit
- Brainstem symptoms
Most cerebral aneurysms are unobserved until they have already ruptured. Diagnostic tests can be used to detect if an aneurysm has or will rupture. Tests are usually acquired after a subarachnoid hemorrhage, to confirm the presence of an aneurysm. CSF usually shows presence of blood.
If an unruptured aneurysm has been discovered in the brain of a patient, there are surgical procedures that can treat the aneurysm.
Previously the most common way was Micro-Vascular Clipping, where the surgeon goes into the brain and cuts off blood flow to the aneurysm. Once this surgery is performed, the clip remains in the patient and prevents any future bleeding. It has been proven to be highly effective, because most aneurysms that are clipped do not return.
More recently: Endovascular repair, most often using a "coil" or coiling and stenting (mesh tubes), is a less invasive way to treat some aneurysms. It is now done in more than half of patients.8
Another, related procedure is called Occlusion. In this surgical procedure, the entire artery involved with an aneurysm is clamped off (occluded). After this is done, a small blood vessel is used to reroute the blood away from the afflicted artery. There are also other forms of treatment for berry aneurysms.
People who have been diagnosed with a berry aneurysm, or any kind of aneurysm, should take steps to control high blood pressure, including smoking cessation and avoidance of cocaine and other drugs that elevate blood pressure.
Complications of a ruptured aneurysm include stroke, vasospasm, subarachnoid hemorrhage and death. Vasospasm is induced by irritating effect of RBCs coming out of ruptured region. These vasospasms can lead to cerebral infarcts. Subarachnoid hemorrhage can lead to communicating hydrocephalus.
Intracranial berry aneurysms are the most common kind of aneurysm in the brain.9 Their incidence is 1 in 10000 people per year (around 27,000 cases per year in the United States). They have a mortality rate of 70–90%. Highest incidence is between 30—60 years of age. It is slightly more common in women.6 They are never seen in pediatric population.2
- Between 10 and 30% of patients with autosomal dominant polycystic kidney disease will develop berry aneurysms.
- Connective tissue disorders, such as Marfan syndrome and Ehler-Danlos syndrome
- Goljan, Edward F. (2006). Rapid Review Pathology (2nd ed.). St. Louis: Mosby. p. 158. ISBN 0-323-04414-X.
- Pathology the big picture. New York: McGraw-Hill Medical. 2008. p. 148. ISBN 0-07-159379-9.
- Stroke essentials for primary care : a practical guide. New York: Humana Press. 2009. pp. 86–88,153. ISBN 978-1-934115-01-5.
- Forensic pathology (2nd ed. ed.). Boca Raton, FL [etc.]: CRC Press. 2001. p. 61. ISBN 0-8493-0072-X.
- "berry aneurysm" at Dorland's Medical Dictionary
- Haberland, Catherine (2007). Clinical neuropathology : text and color atlas ([Online-Ausg.]. ed.). New York: Demos. p. 70. ISBN 978-1-888799-97-2.
- The hands-on guide to imaging. Oxford: Blackwell. 2004. p. 204. ISBN 1-4051-1551-3.
- Neurological differential diagnosis : a prioritized approach (3. Dr. ed.). Oxford: Blackwell Publishing. 2005. p. 133. ISBN 978-1-4051-2039-5.