Hemorrhagic Strokes - Subtypes And Causes Of Stroke: Stroke

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Hemorrhagic strokes

Less than 20% of all strokes are hemorrhagic. A blood vessel in or around the brain bursts, spilling blood into the surrounding tissue. This type of stroke generally occurs in two different anatomical settings: inside the brain (intracerebral hemorrhage) or outside the brain, but inside the skull (extracerebral hemorrhage). Different subtypes of hemorrhagic stroke can occur at each location. Treatment is aimed at stopping the hemorrhage and repairing any damage, and generally involves an inter-arterial procedure, surgery, or medication.

Intracerebral hemorrhage

There are two basic types of intracerebral hemorrhages. The first, deep (hypertensive) hemorrhage, occurs in the deep structures of the brain (see Figure 6). The second type, lobar hemorrhage, occurs in the lobes of the right and left brain hemispheres.

Figure 6: Intracerebral hemorrhagic strokes Hemorrhage means bleeding. When the bleeding takes place within the interior of the brain, as shown in these two examples, the stroke is known as an intracerebral hemorrhage. A hypertensive hemorrhage (A) occurs deep within the brain, often when blood pressure is particularly high. A lobar hemorrhage (B) is generally not caused by hypertension but occurs when blood leaks into one of the four lobes of the brain.

Deep hypertensive hemorrhages. This type of hemorrhage usually strikes people with a history of high blood pressure (hypertension). Symptoms such as headache and vomiting are relentless over a period of minutes. Deep hypertensive hemorrhages can occur at four basic locations: the basal ganglia, thalamus, pons (brainstem), and cerebellum. Cerebellar hemorrhages are often severe enough to result in brainstem compression, coma, and death.

If diagnosed early, a deep hypertensive cerebellar hemorrhage can be treated with surgical removal of the hematoma. Following surgery, chances of rapid recovery are excellent. Surgery is also possible for other subtypes of deep hypertensive hemorrhage, but in these situations, recovery is more limited because the hemorrhage has already caused significant brain damage by the time the problem is diagnosed. Small hemorrhages are better left to heal on their own, and good recovery is possible with careful medical and nursing care through the acute phase.

Lobar hemorrhage. This type of intracerebral hemorrhage takes place when blood leaks into one of the four lobes of the brain: the frontal, parietal, temporal, or occipital lobe. Unlike hypertensive intracerebral hemorrhages, lobar hemorrhages are not necessarily caused by high blood pressure. These strokes generally affect people over 60. Other than age, there are no known risk factors for this type of stroke.

Most people with a lobar hemorrhage have headaches at the site of the bleeding, and more than half vomit or feel drowsy at the onset. Other symptoms depend on which lobe is affected. For instance, a hemorrhage in the occipital lobe can cause vision impairment, whereas bleeding in the frontal lobe can cause weakness in the arm or leg.

There are three types of lobar hemorrhage. The two with known causes often recur and have a genetic basis, so they tend to run in families. The last type, which develops for unknown reasons, does not usually recur.

The first type of lobar hemorrhage is caused by a protein deposited in the blood vessels of the frontal, parietal, occipital, and temporal lobes. The protein deposit weakens the blood vessels so much that they rupture, giving rise to the hemorrhage. Physicians at Massachusetts General Hospital and other institutions are studying ways to prevent this subtype through medical therapy, or treat it once it occurs.

A second type of lobar hemorrhage originates either in an entanglement of blood vessels, particularly between arteries and veins, known as an arteriovenous malformation (AVM), or in tiny angiomas, noncancerous tumors made up of blood vessels. Although many of these lesions are harmless, others may rupture and hemorrhage, causing a stroke. It is possible to eliminate or at least reduce the size of an AVM or angioma with microsurgery, an intra-arterial procedure, or radiation therapy. The method used will depend on the location and nature of the AVM or angioma.

With increased use of CT and MRI imaging in diagnosis, some AVMs are discovered by chance when a doctor has ordered a brain scan for some other reason. It is not clear whether such AVMs pose a high risk of rupture; they may actually pose less of a risk than previously thought. If so, surgery may pose a greater risk than leaving an accidentally discovered AVM untreated.

The third type of lobar hemorrhage is the kind that occurs for some unknown reason and is diagnosed when the other two mechanisms are excluded. This type of lobar hemorrhage does not often recur.

Extracerebral hemorrhage

The brain is covered by three membranes, collectively known as meninges. The dura mater (outer membrane) is tough and fibrous. The pia (innermost layer) is soft, as it is in direct contact with the brain. In between is the arachnoid layer, which is filled with multiple blood vessels and cerebrospinal fluid.

Extracerebral hemorrhages are those that occur in or around one of these three membranes. These hemorrhages cause a stroke when the bleeding is large enough to compress brain tissue or arteries supplying the brain with blood. Several types of extracerebral hemorrhages exist, defined by where they occur.

Subarachnoid hemorrhage. These hemorrhages occur just under the arachnoid membrane. Two types of subarachnoid hemorrhages exist: those caused by berry aneurysms and those caused by infectious aneurysms. As mentioned earlier in this report, aneurysms are bulges in blood vessel walls that can burst, creating the heavy bleeding that is referred to as a hemorrhage.

Berry aneurysms most often occur where major arteries divide at the base of the brain. The blood vessel walls weaken and bulge, forming a berry-shaped aneurysm, and then grow to a point where they become likely candidates for a rupture. The rupture can cause a devastating hemorrhage around the brain, compressing it and damaging tissue. At other times, the rupture may cause a devastating spasm of the vessels at the base of the brain, blocking blood flow and leading to ischemia and ischemic infarction. Berry aneurysms are best eliminated by intra-arterial catheter techniques or surgery (see "Treating hemorrhagic stroke"). They are best treated at institutions that are centers for interventional arterial procedures.

Infectious aneurysms occur in blood vessels located over the surface of the brain, not at its base. They generally result from a tiny embolus from an infected heart valve, in people with bacterial endocarditis. The infectious embolic particle lodges in a blood vessel on the surface of the cortex and infects it. As the blood vessel weakens, an aneurysm develops. Infectious aneurysms are best treated with antibacterial therapy. Occasionally they may have to be surgically excised.

If an aneurysm causes pain or other symptoms, a doctor may be able to diagnose it before it ruptures and does serious damage. An MRI or CT scan may reveal an aneurysm in a large blood vessel, although cerebral angiography, an invasive imaging test, provides more detailed information. An aneurysm is managed best when a team of neurosurgeons, interventional neuroradiologists, and neurologists work together to decide on the most appropriate treatment.

In about 45% of cases, a severe headache is the first major symptom of a subarachnoid hemorrhage. People often characterize the headache as the worst headache they have ever had, using words such as "explode" and "burst" to describe it. About half of people lose consciousness. Other early symptoms may include a stiff neck, nausea and vomiting, trouble concentrating and other kinds of mental impairment, and seizures.

Other extracerebral hemorrhages. Bleeding may also occur in the space underneath the dural lining, known as the subdural space, or above the dural lining, known as the epidural space. Subdural and epidural hemorrhages result from trauma and tear of blood vessels in these areas. Elderly people often have a large subdural space, which develops as a natural aspect of aging. The little venous connections in the subdural space often break, resulting in a slow oozing of blood. Surgical drainage of the blood, to prevent brain compression, may be required in subdural hemorrhages and is usually necessary in epidural hemorrhage.

Last updated:	September 05, 2008