Cerebral hemorrhage: Encyclopedia - Cerebral hemorrhage

Cerebral hemorrhage

A cerebral hemorrhage or hemorrhagic stroke is a form of stroke that occurs when a blood vessel in the brain ruptures or bleeds. Hemorrhagic strokes are deadlier than their more common counterpart, ischemic strokes. Like ischemic strokes, hemorrhagic strokes interrupt the brain's blood supply, but in addition, blood irritates brain tissue, disrupting the delicate chemical balance, and, if the bleeding continues, the increased intracranial pressure can crush brain tissue and restrict blood flow into the brain (NINDS 1999).

Cerebral hemorrhages can be subarachnoid (bleeding into the subarachnoid space, outside the brain) or intracerebral (within the brain itself) (Cicala 1999).

Cerebral hemorrhage - Intracerebral hemorrhage

Intracerebral hemorrhage, or ICH, accounts for 10 to 15 percent of all strokes (Weibers 2001). It most frequently results from high blood pressure as found in people with hypertension, eclampsia, and abuse of some drugs (Liebeskind, 2004). A third of intracerebral bleeds result in intraventricular hemorrhage, or bleeding within the brain's ventricles (Liebeskind, 2004). ICH has a mortality rate of 44 percent after 30 days, higher than ischemic stroke or even the very deadly subarachnoid hemorrhage (Liebeskind, 2004).

Cerebral hemorrhage - Subarachnoid hemorrhage

Subarachnoid hemorrhage, which accounts for 5 to 10 percent of strokes (Weibers 2001) is one of the deadliest type of strokes. While ischemic strokes have a 30-day mortality rate of 20 percent, subarachnoid bleeds kill 40% of their victims in the same time, disabling half the survivors (NINDS 1999; Weibers 2001). When a vessel in the arachnoid layer of the meninges bursts, blood enters the subarachnoid space where cerebrospinal fluid (CSF) bathes the brain, contaminating it. Since the brain is quite sensitive to changes in pH, extensive damage can result when the chemical balance of the CSF is disturbed by the blood (NINDS 1999).

Cerebral hemorrhage - Symptoms of cerebral hemorrhage

A sudden, severe headache is common in hemorrhagic stroke, and is especially indicative of that if accompanied by stiff neck, facial pain, pain between the eyes, vomiting, or altered consciousness (Weibers, 2001). Other signs of hemorrhagic stroke include those that indicate increased intracranial pressure, caused by swelling or collection of blood. These include increased blood pressure, unequal pupils, especially when one pupil is dilated and does not react to light, headache, vomiting, visual disturbances, and decorticate or decerebrate posturing (Yamamoto, 1996).

Cerebral hemorrhage - Pathophysiology

Blood carries plasma proteins, leukocytes and other molecules which damage brain cells when they flood the area. Also, a rise in intracranial pressure exacerbates ischemia by compressing blood vessels and requiring higher blood pressures to force blood into tissues. A positive feedback loop is created: hypoxic tissue swells, and swelling tissue becomes hypoxic (Nurse-Anesthesia.com, 2002).

Cerebral hemorrhage - Treatment

Due to their life-threatening nature, cerebral hemorrhages require immediate neurosurgical evaluation and intervention. Neurosurgeons use specialized examinations for cerebral hemorrhage patients, such as the Hunt and Hess scale, that can help determine the appropriate treatment. Strategies to protect the brain during this type of stroke include blood sugar and blood pressure control, adequate oxygen and intravenous fluids, detection and treatment of the cause of bleeding, and constant monitoring (usually with the Glasgow Coma Scale) and immediate treatment for complications from bleeding into or around the brain.

Cerebral arteriography may be used to determine the cause for bleeding, since some causes may be surgically corrected to reduce the risk of future bleeding. Selected patients with subarachnoid hemorrhage due to a ruptured aneurysm require emergency surgery to "clip" the aneurysm off from the normal brain blood circulation, and they receive nimodipine, a drug shown to reduce incidence of vasospasm, a complication of this type of stroke.

Cerebral hemorrhage - Risk factors

Like ischemic stroke, risk factors for hemorrhagic stroke include inflammation of the heart, hypertension, and arteritis (Weibers 2001). Atherosclerosis, the main risk factor for ischemic stroke (Cicala 1999), also causes heart disease and arterial rupture, so the presence of arterial fatty deposits is a major risk factor for hemorrhagic stroke as well. Factors that pose a risk for hemorrhagic stroke and not ischemic stroke include anticoagulant or thrombolytic therapy, bleeding disorders like hemophilia and thrombocytopenic purpura, arterial dissection, and cocaine use (Weibers 2001).

Intracerebral hemorrhages may be caused by burst aneurysms or arteriovenous malformations, but are most often caused by hypertension, which can cause the delicate blood vessels in the brain to burst (Cicala 1999).

Aneurysm, a weakening and ballooning in the wall of one of the brain's arteries, causes 75-90% of subarachnoid bleeds (Weibers, 2001). Aneurysms may put pressure on the brain tissue, but the real trouble occurs when the weakened wall bursts. The area near the Circle of Willis is a common spot for aneurysms: Small branches off the middle cerebral artery are so prone to burst that they are commonly known as "stroke arteries" (Kapit and Elson, 1977).

Vascular malformations such as arteriovenous malformation (AVM) are another cause of hemorrhagic stroke. AVM is a congenital condition that consists of a tangle of deformed blood vessels and capillaries with thin walls that can rupture (NINDS 1999). These malformations can cause subarachnoid hemorrhage but more commonly responsible for intracerebral bleeding (Weibers 2001). Vascular malformations and aneurysms usually cause no symptoms and can lie undetected until they cause a stroke. On occasion, they can cause "warning leaks" without actually bursting, causing symptoms like seizure, migraine, or one-sided numbness (Weibers 2001).

In moyamoya disease, small blood vessels in a network replace normal blood vessels around base of brain because of stenosis or blockage of large arteries surrounding the brain (Weibers, 2001). These blood vessels are delicate and more likely than normal blood vessels to break and cause hemorrhagic stroke.

Unfortunately, some treatments for ischemic stroke aimed at dissolving the occluding blood clot can increase the likelihood of cerebral hemorrhage. Hemorrhagic transformation is the phenomenon in which blood vessels weakened by ischemic stroke rupture to cause hemorrhage in addition (Stroke Center, 2005; Jauch, 2003). Hemorrhagic transformation can occur without antithrombotics, but they increase the risk (Jauch, 2003).

For poorly understood reasons, pregnancy increases hemorrhagic stroke risk, and women who have just given birth are more than 28 times more likely to suffer hemorrhagic strokes than the average person (NINDS 1999).

Cerebral hemorrhage - Epidemiology

Though ischemic strokes are more common, the young, though only a small percentage of stroke sufferers, are more likely to have hemorrhagic strokes than ischemic strokes (NINDS 1999).

Adapted from the Wikipedia article "Cerebral hemorrhage", under the G.N U Free Docmentation License. Please also see http://en.wikipedia.org/wiki