As in the case of brain haemorrhage (which is one of the forms of a stroke), the cause of subarachnoid haemorrhage is a blood vessel rupture. This disorder differs from brain haemorrhage since the blood expands on the surface of the brain and does not cram into brain tissue alone.
On the surface of the brain there are three thin, membranous envelopes (meninge) covering the brain. A membrane on the surface (dura) adheres to the skull, while the deepest membrane (pia) adheres to the brain; the middle membrane (arachnoidea) is located immediately next to the dura, so there is space between the arachnoid and the pia, the so-called “subarachnoid” space, filled with fluid.
Subarachnoid haemorrhage occurs when a blood enters the subarachnoid space. The cause of this is usually ruptured aneurysm in the cerebral artery wall. The blood is retained in the fluid or gradually flows through the pia into the brain tissue.
The main symptom is a sudden headache, which is usually more painful than ordinary headaches, or even migraines. After that, other symptoms such as neck stiffness or photophobia follow, and can be accompanied by unconsciousness, dizziness, confusion, headache, nausea and vomiting. In severe seizures an affected person can suddenly lose consciousness.
Out of the 12 cases of vascular disorders in the brain, one is caused by subarachnoid bleeding. It is most common in people between the ages of 40 and 60, and more often in women than in men. People with high blood pressure are particularly susceptible.
Severe seizures (which cause unconsciousness) can be fatal (up to 45% of cases), and one of the three who survives the first seizure gets further seizures. Because of the blood pressure on the brain tissue, there is a danger of permanent brain damage. In about half the cases, blood spreads to the brain and causes symptoms similar to stroke.
What to do?
If you suddenly feel a severe headache, especially if it is accompanied by a stiff neck and a sensitivity to light, call your doctor immediately. If someone in your presence complaints about a sudden headache and then becomes unconscious, there are two possible causes – stroke or subarachnoid bleeding. In any case, apply the first aid measures until the doctor comes in.
Faced with an unconscious person, the doctor will first of all take care of the life functions – ensure that there is no stopping in breathing. After the patient is out of danger, a correct diagnosis should be made. If the physical examination indicates the possibility of subarachnoid haemorrhage, the best way to confirm the diagnosis is lumbar puncture, i.e. taking samples of a cerebrospinal fluid. This watery fluid circulates in the subarachnoid space on the brain and spinal cord, and the lumbar region (area in the lower part of the spine) is the easiest place to take the sample to see if it contains blood.
If blood is found in the cerebro-spinal fluid, the doctor will first and foremost try to prevent further bleeding. The artery rupture cannot be cured with any medication,but if the patient survives a few days after the subarachnoid hemorrhage, the rupture that caused the disorder has probably closed (at least temporarily) with natural blood clotting and started to heal. Treatment basically implies a few weeks of resting in bed, usually in the hospital. During this period, a doctor may prescribe pain relief for the patient, e.g. paracetamol due to headache.
If the blood pressure is high, the patient will need to take a betablocker or diuretic. Within three days of brain artery seizures, it will probably be necessary to record it X-ray technique (arteriogram) to determine the site of aneurysm, as well as any other damage to the wall. If arteriograms point to the risk of further seizures, a surgical procedure may be needed to prevent further blood leakage – meaning, closing the aneurism with a small metal or plastic clamp.
If you regain consciousness after a severe seizure and survive for six months without any further problems, you are probably out of danger. A surgical procedure also provides good prospects for complete recovery. Remaining (residual) symptoms after seizures are different depending on the affected part of the brain. A patient may be partially paralyzed for some time (in some cases and permanently), feel weakness and numbness; the same applies to visual and speech disorders (for further information on these issues, see the article on stroke). Regular blood pressure should be controlled after initial seizures; high blood pressure can exacerbate already weak blood vessel wall.