A subarachnoid hemorrhage is an uncommon type of stroke that involves bleeding in the subarachnoid space, the space between the brain and its surrounding membrane.

The most common cause of subarachnoid hemorrhage is a brain aneurysm. An aneurysm is a protruding bubble or sac on a blood vessel that has thin, weak walls and a tendency to rupture with time. When an aneurysm erupts, it quickly bleeds into the brain. Other causes may include bleeding from an arteriovenous malformation, brain infection or tumors and vasculitis where blood vessels inside the brain become inflamed.

Women are more likely to develop subarachnoid hemorrhages, and it may occur at any age, but it’s most common between the age of 45 and 70. People who smoke or consume excessive amounts of alcohol, and those with high blood pressure are more likely to develop brain aneurysms, and thus subarachnoid hemorrhage.

The pathophysiology of subarachnoid hemorrhage starts when there is a defect in the walls of arteries that leads to the formation of an aneurysm; hydrostatic pressure from the arterial blood expands the aneurysm and, if left untreated, may rupture and cause bleeding into the subarachnoid space, which spreads through the cerebrospinal fluid around the brain and spinal cord. Blood in the cerebrospinal fluid increases the pressure on the brain and may cause serious signs and symptoms.

A sudden severe headache, often characterized as "the worst headache ever felt”, is the most common symptom that occurs in people with a subarachnoid hemorrhage. Other symptoms include vision problems, vomiting, fainting, neck stiffness and low back pain due to irritation of nerve roots in the lower back.

Subarachnoid hemorrhage is often suspected during a physical exam when symptoms such as neck stiffness and vision problems are detected, or when a sudden, severe headache is reported. Confirming the presence of the condition may need more testing; further testing starts usually with a computerized tomography (CT) scan of the head to look for bleeding in the brain. If the result is not clear enough, the doctor may use a contrast dye during the procedure. Other tests include magnetic resonance imaging (MRI), lumbar puncture and cerebral angiography.

Subarachnoid hemorrhage is life-threatening; hence a rapid treatment is important to safe the person’s life. The treatment is required to resolve the cause of bleeding, relieve symptoms and prevent complications such as permanent brain damage. Medication can be effective in relieving the symptoms; some medications used are nimodipine to treat the reduced blood supply to the brain, pain-relievers for the severe headache, and anticonvulsants for seizures if they occur. Surgery or a technique called endovascular coiling to repair the damaged blood vessels and avoid further bleeding from the aneurysm may be suggested.

Even after subarachnoid hemorrhage treatment, patients are still at risk for related complications. The most common complication is called rebleeding, which happens when a rupture that has healed ruptures again. In some cases, people may experience other complications including vasospasm and hydrocephalus. Vasospasm refers to narrowed blood vessels in the brain limiting blood flow, while hydrocephalus is a buildup of fluid in the brain.

Since aneurysms are the main cause of subarachnoid hemorrhage, identifying, preventing and successfully treating aneurysms can reduce the risk of developing the condition. Stopping smoking, reducing alcohol consumption, and taking steps to prevent high blood pressure can be effective in lowering the chance of having a subarachnoid hemorrhage resulting from an aneurysm.

People with subarachnoid hemorrhage can recover completely after treatment, and the prognosis of the condition depends on a number of different factors, such as the location and amount of bleeding, complications that occurred and older age. More severe symptoms are usually an indication of a poorer prognosis.

A review recently published in the British Journal of Neurology, Neurosurgery and Psychiatry, shows the overall incidence of subarachnoid hemorrhage at approximately 9 per 100,000 persons.

A subarachnoid hemorrhage is uncommon type of stroke characterized by bleeding in the subarachnoid space between the brain and the thin tissues that cover it. Subarachnoid hemorrhages can be fatal, but with proper and rapid treatment, sever complications can be averted.

There are many causes that can lead to bleeding in the subarachnoid space. The causes of a subarachnoid hemorrhage include:

·        Cerebral aneurysm: Cerebral aneurysms are the most common cause of subarachnoid hemorrhage. A cerebral or intracranial aneurysm is a ballooning of a weakened region of a blood vessel in the brain. The aneurysm can continue to expand if left untreated, and will eventually rupture and bleed into the brain. Aneurysms are treatable, but are hard to detect because they usually cause no symptoms until they rupture.

·        Arteriovenous malformations: This is a bundle of abnormally formed blood vessels which may lead to rupture or bleeding into the brain.

·        Tumors: Cancerous and non-cancerous brain tumors can damage blood vessels and cause a subarachnoid hemorrhage.

·        Infection: Brain infections, such as encephalitis, can lead to a subarachnoid hemorrhage.

·        Vasculitis: This is a condition where the blood vessels inside the brain become inflamed due to a wide range of problems, such as infections or autoimmune diseases.

·        Moyamoya disease: An uncommon condition, moyamoya causes blockages inside the brain's arteries.

·        Fibromuscular dysplasia: This is a rare condition that can cause the arteries to get thinner.

• Head injuries: Head injuries from motor vehicle crashes are the most common injury leading to subarachnoid hemorrhage among adults. The condition is also often seen in older people who suffer head injuries from falls.

There are several risk factors that can increase the risk for subarachnoid hemorrhage:

• Aneurysms: Having an aneurysm is the most significant risk factor for developing subarachnoid hemorrhage. The risk factors for aneurysms include:

• Cigarette smoking
• High blood pressure
• Heavy alcohol consumption
• A family history of aneurysms
• Abnormal connective tissue, such as Marfan syndrome

• Age: It can happen at any age but it is more common in people between 45 and 70 years of age.
• Gender: Women are slightly more affected by subarachnoid hemorrhage than men.
• Race: Subarachnoid hemorrhage is more common in Japanese or Finnish descent. Occurrence is also high in the African race compared to other ethnic groups, because they are more likely to have high blood pressure.

Subarachnoid hemorrhage occurs when blood is released into the subarachnoid space, which surrounds the brain and spinal cord. Bleeding usually happens when a cerebral aneurysm ruptures, but it can result from other events that affect blood vessels in the brain like arteriovenous malformation and head injuries.

Blood in the subarachnoid space quickly circulates around the brain and spinal cord through the cerebrospinal fluid, which can cause meningeal irritation due to direct damage to local tissue or to an increase in intracranial pressure.

Aneurysms usually occur in the terminal portion of the internal carotid artery and the branching sites on the large cerebral arteries in the anterior portion of the circle of Willis, which is an anastomotic system of arteries that sits at the base of the brain. Aneurysms develop when there is a defect in the arterial wall that leads to formation of a bulge, which expands as a result of hydrostatic pressure from arterial blood.

The main symptoms of subarachnoid hemorrhages include:

• A sudden, severe headache that may be likened to a hit on the head.
• Neck stiffness and low back pain due to irritation of nerve roots in the lower back.
• Feeling and being sick
• Sensitivity to light.
• Blurred or double vision.
• Numbness in part of the body.
• Stroke-like symptoms, such as slurred speech.
• Decreased consciousness and alertness.
• Seizures.

The diagnosis of subarachnoid hemorrhage may include:

• CT scan: CT scans are used to detect bleeding in the brain. Often, CT scans without contrast dye will be performed immediately, but the doctor may inject a contrast dye to view blood vessels more clearly, a diagnostic test called CT angiogram.

• Lumbar puncture: This test is usually ordered when a subarachnoid hemorrhage is suspected but the bleeding does not appear on a CT scan. Lumbar puncture involves inserting a needle into the lower part of the spine to withdraw a small amount of cerebrospinal fluid. The sample is then analyzed to look for the presence of bleeding.

• MRI: MRIs help detect bleeding in the brain and the underlying cause for the bleeding, so they are also useful in planning treatment. Doctors may inject a dye to view blood vessels and blood circulation in the brain more clearly.

• Cerebral angiography: The doctor in this test inserts a long, thin catheter or tube into an artery in the leg of the patient and threads it to the brain. Then he injects dye into the blood vessels to make them visible under X-ray imaging.

A subarachnoid hemorrhage is a medical emergency and should be treated accordingly. Treatment is based on the cause and severity of the condition. Treatment of subarachnoid hemorrhage include:

Initial Treatment

Treatment starts with supporting the vital functions of the patient, such as breathing, blood pressure and circulation. Patients with severe cases may be put in an intensive care unit.

Medications

Medications used for patients with subarachnoid hemorrhage include:

• Nimodipine: This drug may be given to reduce the risk of delayed cerebral ischemia, where the supply of blood to the brain becomes reduced due to subarachnoid hemorrhage.
• Pain relievers: Morphine and a combination of codeine and paracetamol are commonly prescribed for the severe headache often associated with a subarachnoid hemorrhage.
• Anticonvulsants: Treatments for subarachnoid hemorrhage may include anticonvulsants, such as phenytoin, to avoid seizures.
• Antiemetics: Medications like promethazine can reduce or prevent nausea and vomiting that may accompany a subarachnoid hemorrhage.

Procedures

Procedures are often performed if diagnostic scans show that subarachnoid hemorrhage is the result of a ruptured aneurysm to repair the damaged blood vessels and prevent the aneurysm from bleeding again. Procedures include:

• Cerebral aneurysm repair by clipping

This surgery is done under general anesthesia. The surgeon makes an opening in the scalp and a small flap of bone is removed. When the aneurysm is located, the surgeon places a metal clip that stays permanently clamped on the aneurysm, preventing it from growing further or rupturing again.

• Endovascular coiling

This procedure is also done under general anesthetic. It involves inserting a catheter into an artery in the leg or groin, and guiding it until it reaches the aneurysm in the brain using X-ray imaging. Tiny platinum coils are then passed through the tube to fill the aneurysm. Once the aneurysm is full of coils, blood flow into the aneurysm is reduced, preventing it from growing or rupturing again.

Usually, a patient who had a subarachnoid hemorrhage will develop further problems. Complications may include:

• Rebleeding

Recurrent bleeding is the most serious complication of subarachnoid hemorrhage. It occurs when the cerebral aneurysm bursts again after it has sealed. This risk is high in the few days after the first hemorrhage, and carries a high risk of permanent disability or death.

• Delayed cerebral ischemia

This condition typically occurs in the few days following the first hemorrhage. It happens when the supply of blood to the brain is dangerously reduced, disrupting the normal functions of the brain and causing brain damage. Vasospasm, the constriction of blood vessels in the brain, may be a factor. Delayed cerebral ischemia affect the level of consciousness, and can lead to a coma.

• Hydrocephalus

Hydrocephalus, which is the abnormal buildup of cerebrospinal fluid in the brain, is common after subarachnoid hemorrhage because the damage caused by the hemorrhage can disrupt the production and drainage of cerebrospinal fluid. Hydrocephalus can increase pressure and cause further brain damage.

• Long-term complications

There are a number of longstanding conditions that can affect people after a subarachnoid hemorrhage. These include:

• Epilepsy

Epilepsy is a condition where the abnormal electrical discharges occur in the brain, causing a person to have repeated seizures. Usually, the first seizure related to subarachnoid hemorrhage occurs in the first year after the hemorrhage.

• Cognitive dysfunction

This complication commonly occurs when a person faces difficulties with one or more brain functions, such as memory, concentration and planning. Most cognitive functions return to normal with time, but problems with memory can persist.

• Emotional problems

These common, long-term complications of a subarachnoid hemorrhage include a range of problems such as depression and anxiety disorder.

The best way to prevent a subarachnoid hemorrhage is by treating cerebral aneurysms, but that is not always possible because aneurysms can be hard to detect. The three most effective steps to reduce the chance of having a subarachnoid hemorrhage due to an aneurysm are:

• Stopping smoking
• Reducing alcohol consumption
• Taking steps to prevent high blood pressure such as regular exercise, eating a healthy diet.

Treatment of an aneurysm that has already ruptured can help prevent rebleeding.

Although the prognosis for patients with subarachnoid hemorrhage has improved in the last few years, around 50% of sufferers may die or be left with impaired brain function, according to the British National Health Service.

Complete recovery is possible after treatment, and how well a person with subarachnoid hemorrhage does depends on the location and amount of bleeding, the emergence of complications and older age. More severe symptoms are associated with a poorer prognosis.

The British Journal of Neurology, Neurosurgery and Psychiatry, published a review that shows the overall incidence of subarachnoid hemorrhage at approximately 9 per 100,000 people. Rates of the subarachnoid hemorrhages are higher in Japan and Finland and increase with age.