A Subarachnoid Hemorrhage

What Is A Subarachnoid Hemorrhage? What Causes A Subarachnoid Hemorrhage?

A subarachnoid hemorrhage is when blood leaks into the space between two membranes that surround the brain - it is an uncommon cause of a stroke. The bleeding occurs in the arteries just below the arachnoid membrane and above the pia mater - just below the surface of the skull. There are three membranes that surround the brain, the pia mater is the innermost one while the arachnoid is the middle one.

The bleeding may occur spontaneously, typically from a ruptured cerebral aneurysm, or because of a head injury. An aneurysm is a bulge that develops in a blood vessel caused by a weakness in the blood vessel wall. As is the case with any stroke, a subarachnoid hemorrhage is a medical emergency - the risk of complications, brain damage and even death is considerable.

The subarachnoid space is filled with cerebrospinal fluid. During a subarachnoid hemorrhage the cerebrospinal fluid in the subarachnoid space becomes bloody. According to the NIH (National Institutes of Health), USA, almost half of all hospitalized subarachnoid hemorrhage patients die within four weeks, while a significant number of those who survive do so with severe disabilities. Between 10% to 15% of people who have this type of stroke die before they reach hospital.

People who have a first-degree relative who had a subarachnoid hemorrhage have a higher risk of developing one themselves, compared to other individuals, as do smokers, heavy regular alcohol drinkers, and those with hypertension (high blood pressure).

Subarachnoid hemorrhages make up about 5% of all strokes. Even though they are uncommon, they are responsible for approximately one quarter of all deaths caused by or related to strokes. Middle aged individuals and females are more likely to be affected.

What are the signs and symptoms of subarachnoid hemorrhage?

  • A sudden headache, which is usually severe. Patients describe the pain as similar to receiving a blow on the head - a thunderclap headache. This headache typically pulsates towards the occipult (back of the head).
  • Stiff neck
  • Nausea
  • Vomiting
  • Slurred speech
  • Depression, confusion, delirium, and possibly apathy
  • Impaired consciousness, sometimes total loss of consciousness
  • Seizures (in about 1 in every 14 cases)
  • Sometimes there may be intraocular hemorrhage (bleeding into the eyeball)
  • Some patients may find it hard to lift an eyelid
  • Sharp increase in blood pressure
The headache and stiff neck may make some people believe they have meningitis. However, a subarachnoid hemorrhage has no fever or skin rash, while meningitis does.

What are the causes of subarachnoid hemorrhage?

Aneurysm
Between 70% and 85% of subarachnoid hemorrhage cases are caused by the rupture of a cerebral aneurysm. An aneurysm is when part of a blood vessel swells, which in this case is because there is a weakness in the wall of the blood vessel. As blood pressure accumulates it balloons out at its weakest point. The larger the swelling gets, the greater its risk of bursting (rupturing).

Aneurysms associated with subarachnoid hemorrhages tend to occur in the circle of Willis and its branches - a circle of arteries that supply blood to the brain.

About 1% of people have a congenital defect which affects their blood vessels in the brain. Some blood vessels have weak and thin walls which bulge outwards easily - these people are more susceptible to aneurysms.

There is a greater risk of an aneurysm rupturing if you smoke, drink alcohol regularly in large quantities, and suffer from hypertension (high blood pressure) and do not control it properly.

In most cases an aneurysm will heal itself and the bleeding will cease. However, if left untreated, the risk of an aneurysm recurrence in the same place is much greater.

Arteriovenous malformations

This is a congenital disorder, the individual is born with it. It is a disorder of blood vessels in the spinal cord, brainstem or brain. A complex, tangled web of abnormal arteries and veins develop, they communicate with each other abnormally (connected by fistulas). Experts say this congenital disorder occurs because of a problem during fetal development in the womb. Those with arteriovenous malformations have no symptoms until a hemorrhage occurs. About 10% of all subarachnoid hemorrhages are caused by arteriovenous malformations.

Head injury

A severe head injury can also be a cause of a subarachnoid hemorrhage.

Diagnosing a Subarachnoid Hemorrhage

Symptoms of a stiff neck and severe headache should alert any competent health care professional about the possibility of a subarachnoid hemorrhage. The patient may be referred to the hospital's specialist neurologist or its neurosurgical unit where further diagnostic tests will be performed.

MRI (magnetic resonance imaging) scan - this provides a detailed image of the inside of a person, which in this case would be inside their skull. This diagnostic test may help identify blood vessel problems, and even the hemorrhage.

Lumbar puncture - a sample of cerebrospinal fluid is taken from the lower end of the spine with a needle to determine whether there is any blood.

Doppler ultrasound - ultrasound is used to monitor the flow of blood in the brain. Unusual changes in bloodflow speed could indicate that the arteries in the brain have gone into spasm (cerebral vasospasm), which can result in further hemorrhaging. If this is detected, the patient needs to be treated immediately.

CT (Computerised tomography) scan - this imaging device can detect where blood is around the brain and any possible problems that may result from that. A colored die may be injected into the blood to find out where the bleeding is coming from.

What are the treatment options for a a Subarachnoid Hemorrhage?

Preventing cerebral vascospasm - to prevent blood vessels near the ruptured aneurysm from going into spasm, the patient may be given nimodipine for about three weeks. This medication is for hypertension (high blood pressure), but it also prevents spasms.

Headache - initially, because the pain is so severe, the patient may be given morphine. As symptoms improve the doctors may switch to other painkillers.

Neurosurgical clipping - this is a surgical intervention to seal the aneurysm shut with a small metal clip.

Endovascular coiling - a catheter or small plastic tube is inserted into an artery, usually in the patient's groin or leg, it is threaded through blood vessels until it reaches the part of the brain where the aneurysm is located. Platinum coils are pushed through the tube into the aneurysm and cut off the flow of blood into the aneurysm, effectively stopping the hemorrhage. This intervention has a higher success rate and the patient recovers more quickly, compared to neurological clipping.

What are the possible complications of A Subarachnoid Hemorrhage?

Cerebral vasospasm - the blood vessel near the aneurysm goes into spasm, making the hemorrhaging worse. Experts say this is the most dangerous complication. Unfortunately, approximately half of all patients with a subarachnoid hemorrhage have this complication. 1 in 5 deaths from subarachnoid hemorrhage occur because of cerebral vasospasm.

Giving the patient nimodipine helps reduce the risk of this complication significantly.

If left untreated, the patient can go into coma and die.

In cases of vasospam it is important to maintain good blood flow to the brain. Doctors may achieve this by pumping fluids into the blood (hypervolemia), raising blood pressure (hypertension), and transfusing blood and plasma into the body (hemodilution) - this is known as "Triple H Therapy" (hpervolemia, hemodilution and hypertension). If this does not work a small balloon may be implanted in an artery, which is then inflated, to bring the blood supply back.

Epilepsy - about 1 in every 20 patients will eventually develop epilepsy, usually within 12 months of the subarachnoid hemorrhage. If the patient is epilepsy-free for 24 months after the subarachnoid hemorrhage, he/she will probably be epilepsy free forever.

Hydrocephalus - too much cerebrospinal fluid builds up in the ventricles in the brain, placing pressure on the brain which can damage it. If the pressure rises to high the doctor may have to drain some of it by placing a tube (shunt) into the brain.

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