What is a subarachnoid hemorrhage (SAH)?
A subarachnoid hemorrhage (SAH) is a sudden leak of blood over the surface of the brain. The brain is covered by layers of membranes, one of which is called the arachnoid. An SAH occurs beneath this layer. The blood vessels supplying blood to the brain lie in this space, surrounded by clear cerebrospinal fluid.
SAH is a medical emergency. It is a serious, life-threatening condition.
What causes SAHs?
In 75% of cases, there is a weakness in the wall of one of the blood vessels supplying blood to the brain. The resulting balloon-like swelling is called an aneurysm. The hemorrhage occurs when the aneurysm wall tears because of the pressure of the blood as it is pumped through the brain. When this happens, blood bursts into the surrounding brain tissue.
A very small number of SAHs are caused by arteriovenous malformations (AVMs). AVMs are an abnormal arrangement of blood vessels in the head.Are there warning signs?
Are there warning signs?
Very rarely, an aneurysm can press on a particular part of the brain and symptoms might develop as a result. However, usually, aneurysms go undetected and there are no symptoms until they burst.
There is no reason why the hemorrhage occurs on one day rather than another. The bleed often, though not always, happens at a time of physical effort like coughing, going to the toilet, heavy lifting, straining, or during sex.
What are the symptoms?
Most people have a sudden, severe headache, often at the back of the head, followed by vomiting (being sick). The headache usually persists for more than an hour. People usually describe it as the worst headache they have ever had. It is common to have a stiff neck. People might also slur their speech, experience a disturbance in their vision, or have physical problems like weakness in an arm or leg.
In more severe cases, people can collapse and lose consciousness. Some people might also have a seizure (a “fit”).
What happens in hospital?
Most people are admitted to a hospital where the hemorrhage is confirmed by a CT scan of the brain. You might also have a sample of fluid taken from your spine (lumbar puncture).
You will be admitted to a neurosurgical ward for further investigations, which could include an angiogram, an MRI scan, an MRA scan, or a CTA scan (see below). After an SAH there is a risk that the blood vessels in the brain will contract suddenly and block the blood supply to the brain. This might cause a stroke. The sudden contraction of blood vessels is called vasospasm.
An angiogram is an X-ray test used to produce pictures of blood vessels. A cerebral angiogram shows the blood vessels in your head and neck.
An angiogram is the key test for SAH.
After you have had a local anaesthetic, a very small, flexible tube (catheter) is inserted into the blood vessel in your groin (the femoral artery). This is passed through other blood vessels in your body until it reaches your neck. You will not feel it moving inside you.
The tube will be positioned into different blood vessels in the neck.
The aim of treatment is to prevent bleeding or re-bleeding. There are different possible treatments and the decision about which particular method should be used is made by a neurosurgeon, an interventional neuroradiologist (a specialist who treats aneurysms via the blood vessels), and other members of the health care team, in discussion with you and your family.
The chosen method will be the one most suitable for your particular situation and will depend on a number of factors, including the size and position of the aneurysm. Conservative management
The decision to go ahead with a treatment is made when the benefits are deemed to outweigh any possible risks. Due to the individual nature of SAHs, it might be that a decision is made not to go ahead with any interventional aneurysm treatment like coiling or clipping (see below). Instead, you will be managed “conservatively”. In 20% of SAH cases no aneurysm is found and this is often referred to as idiopathic (no known cause) or negative angiogram SAH. Treatment will focus on managing your symptoms and recovery. (You might like to read the sections on Going Home and Recovery.)
In the 1990s, coiling was introduced as a way of treating ruptured and unruptured aneurysms without the need for a craniotomy. Coiling involves approaching the aneurysm from inside the blood vessel, avoiding the need to open the skull. Small metal coils are inserted into the aneurysm through the arteries that run from the groin to the brain. The coils remain in the aneurysm: they are not removed. They prevent blood flowing into the aneurysm and therefore reduce the risk of a bleed or a re-bleed. Blood then clots around the coils sealing off the weakened area.
Coiling is the most common treatment for SAH.
What happens before the procedure?
Although the coiling procedure is similar to an angiogram, involving a catheter being fed up to the brain via the femoral artery, it is much more complex and is carried out under a general anesthesia.
This means you must not eat or drink anything for four to six hours before the procedure. The staff on the ward will advise you on this. On arrival at the radiology department, an anesthetist will give you a general anesthetic and you will be asleep throughout the procedure.
What happens during the procedure?
The room will have several large pieces of high-technology scanning equipment which are needed to perform the coiling.
The radiologist will make a small incision in your groin through which they will insert the small tube into your femoral artery. This is then guided through other blood vessels in your body until it reaches your neck and then into your brain.
Using a guide wire, one by one, the coils are slowly inserted into the aneurysm. The coils are made of platinum, are twice the width of a human hair, and can vary in length. The number of coils needed depends on the size of the aneurysm. The largest coil is inserted first and then smaller coils are inserted until the aneurysm is filled. Usually, several coils will be used.
Each coil has a small electric current passed through it to detach it from the guide wire. This small current also helps the blood to clot and helps to seal the aneurysm. The radiologist will remove the catheter. Occasionally, the entry point in the groin will need to be sealed or stitched. It might be slightly painful, and there might be some bruising.
Coiling is a complex and delicate procedure that will take at least three hours and often longer.
What happens after the procedure?
You will probably spend some time in the high dependency unit – usually at least two hours.
During this time, regular neurological observations will be performed by the nursing staff. This is to check that you are waking up properly from the anesthetic. It involves asking you simple questions, testing the strength of your arms and legs, and shining a light in your eyes. Your blood pressure, heart rate, respiratory rate, and oxygen levels will also be monitored.
The nurse will check the small wound in your groin for any bleeding and also check the pulse in your foot. This is to ensure that your blood circulation to your legs has not been affected.
It might be that the opening in the artery in your groin is plugged closed after the procedure.
You will have to lie flat, or at an angle of no more than 30 degrees, for at least six hours following the procedure. This helps with your blood pressure and prevents any excess pressure on the artery, which could increase the chance of bleeding at the puncture site in your groin. Depending on your recovery after this time, you will be able to sit up gradually. The nurses will assist you with this.
Throughout this time, the nurses on the ward will continue to monitor you and carry out neurological observations. Pain-killers will be given for any discomfort or headaches you might be experiencing. You are also likely to have a drip to prevent dehydration, and possibly a urinary catheter. Because you are restricted to bed rest, you will have to wear pressure stockings to help prevent blood clots forming in your legs (deep vein thrombosis).
What are the risks of coiling?
It is likely that the benefits of coiling will strongly outweigh any possible risks, and your doctor will have discussed this with you fully before you give your consent to go ahead with the procedure.
However, as with any invasive procedure, there are certain risks associated with coiling. Possible complications include stroke-like symptoms such as weakness or numbness in an arm or leg, problems with speech, or problems with vision.
There is also a risk of bleeding, infection or arterial damage at the entry site in the groin.
How successful is coiling?
Research is still being conducted to explore the benefits and risks of coiling. Various studies have been published. The largest is the International Subarachnoid Aneurysm Trial (ISAT) which was established to explore the effectiveness of coiling compared to clipping (see below) of ruptured aneurysms. The trial involved different neurosurgical centers and a total of 2,143 patients participated. The ISAT trial showed that the long-term risks of further bleeding are low for both coiling and clipping, and the results positively supported coiling as a treatment for ruptured aneurysms, both in terms of survival and in the reduction of long-term disability.
The National Institute for Health and Clinical Excellence (NICE) have approved coiling as a treatment of ruptured aneurysms and has published guidelines on the procedure.