| Spontaneous subarachnoid (pronounced | | | | causes bleeding by piercing a blood-vessel on its way |
| sub-uh-RACK-noid) hemorrhage is rightfully the most | | | | to the subarachnoid space, the test might give the |
| feared cause of sudden headache. Usually due to | | | | false impression that a subarachnoid hemorrhage |
| rupture of aneurysms (abnormal, balloon-like | | | | occurred when it hadn't. |
| outpouchings of arteries) located near the base of the | | | | After discovery of subarachnoid hemorrhage, the next |
| brain, subarachnoid hemorrhages involve bleeding into | | | | round of testing focuses on where exactly the |
| the space between the brain and its surrounding | | | | bleeding occurred. While in over two-thirds of the |
| membrane, known as the meninges. A traumatic blow | | | | cases it originates from ruptured aneurysms, other |
| to the head can also cause subarachnoid hemorrhage, | | | | potential sources include tangles of abnormal |
| but this is a completely unrelated process and is not | | | | blood-vessels known as arteriovenous malformations |
| the subject of this essay. | | | | or from bleeds within the brain tissue that secondarily |
| About 10% of people with spontaneous subarachnoid | | | | leak into the subarachnoid space. The managing |
| hemorrhages die before they even get to a hospital | | | | physician can order any of three tests to image the |
| and over a third die within the first four weeks | | | | blood vessels themselves and pinpoint the source of |
| following the bleed. Survivors can have significant | | | | bleeding. |
| impairments due to brain damage. | | | | The oldest test--still considered the gold-standard--is |
| And while the effects of the initial bleed are bad | | | | known as an arteriogram or, alternatively, an |
| enough, in the following few weeks individuals with | | | | angiogram. An arteriogram is considered an "invasive" |
| subarachnoid hemorrhage can suffer additional, serious | | | | test because the doctor must slide a long, flexible |
| complications. One complication is that the aneurysm | | | | catheter through the arterial system (which is under |
| responsible for the initial hemorrhage can bleed a | | | | much higher pressure than the veins) so that dye |
| second time and cause even more damage. This | | | | infused through the catheter will enter the arteries in |
| occurs in 4% of cases within the first 24 hours and | | | | question. Two newer tests are "non-invasive," though, |
| there is another 1.2% chance of re-bleeding each day | | | | in truth, they often involve an infusion into a vein. One is |
| thereafter for the first two weeks. Thus, without | | | | magnetic resonance arteriography (MRA) which is |
| treatment 20% of cases have a second hemorrhage | | | | performed with the help of an MRI-scanner. The other |
| within the first two weeks. | | | | is computed tomographic arteriography (CT-A) which |
| The other serious complication is that the blood | | | | is performed with the help of a CT-scanner. While the |
| deposited in the subarachnoid space can cause | | | | non-invasive tests are getting better all the time, they |
| otherwise healthy arteries passing through this space | | | | still occasionally miss aneurysms otherwise visible on |
| to go into spasm. The spasm decreases blood-flow to | | | | arteriograms. |
| the parts of the brain ordinarily nourished by these | | | | Apart from identifying the bleeding aneurysms, these |
| arteries and thereby inflicts additional damage. Or, said | | | | tests can detect additional aneurysms, when present. |
| another way, a blocked artery causes a new stroke, | | | | About 20% of people experiencing a ruptured |
| this time of the non-bleeding type. For reasons that are | | | | aneurysm have one or more co-existing, unruptured |
| not entirely understood, these spasms of the arteries | | | | aneurysms. |
| do not occur within the first few days after the initial | | | | Subarachnoid hemorrhages occur annually in about 10 |
| hemorrhage. Instead, they typically develop after a | | | | people out of 100,000. This computes to a 0.01% rate |
| delay of 4-9 days. | | | | of annual occurrence. Contrast this figure with the 12% |
| What can be done to reduce these complications? In | | | | of the adult population who have migraine (most of |
| the case of blood-vessel spasm, the best treatment is | | | | whom have at least one severe headache per year) |
| a preventive one. Administering a drug called | | | | and it is apparent that the vast majority of severe |
| nimodipine (prononounced nye-MO-dih-peen) | | | | headaches are not due to ruptured aneurysms. But the |
| intravenously makes spasming less likely to occur. But | | | | concern about missing a ruptured aneurysm means |
| in order to prevent the other major complication, | | | | that many people without subarachnoid hemorrhage |
| re-bleeding, the best treatments are those which | | | | must receive tests in order to diagnose the few who |
| physically stabilize the aneurysm. In one such | | | | have it. |
| procedure, a surgeon places a metal clip across the | | | | What causes aneurysms in the first place? More than |
| aneurysm where it joins the otherwise normal artery. | | | | one factor is involved. First, there can be an inborn |
| An alternative surgery is to wrap the outside of the | | | | weakening of the artery's wall. When the wall |
| aneurysm with surgical gauze or plastic sheeting. A | | | | subsequently deteriorates in ways that can be |
| newer procedure involves filling the aneurysm with tiny | | | | accelerated by hypertension and smoking, an |
| metal coils inserted via a flexible catheter snaked | | | | aneurysm can form. |
| through the arteries. | | | | Actually, aneurysms affecting the brain's arteries are |
| How can one tell if a particular headache is caused by | | | | fairly common. Autopsy and arteriogram studies |
| a bleeding aneurysm? It can be a tough call, but certain | | | | indicate that about 1-4% of the general population have |
| features make a ruptured aneurysm more likely. First, | | | | them. This is many more people than have |
| a headache due to a ruptured aneurysm is typically of | | | | subarachnoid hemorrhages, so a logical conclusion is |
| very abrupt onset (often described as a "thunderclap") | | | | that most people with aneurysms go through their |
| and is classically the worst headache of one's life. In | | | | entire lifetimes without having symptoms. Studies show |
| people who already have recurrent severe headaches | | | | that aneurysms less than 5 millimeters (0.2 inches) in |
| from other causes, the headache due to a ruptured | | | | diameter have a very low rate of rupture, while |
| aneurysm might feel different from the more usual | | | | aneurysms greater than 10 millimeters (0.4 inches) in |
| attacks. | | | | diameter have a significant risk of bleeding. |
| Medical evaluation of patients with ruptured aneurysms | | | | Do ruptured aneurysms run in families? A 2005 report |
| can turn up additional clues, like a stiffened neck or | | | | from the Scottish Aneurysm Study Group showed a |
| changes in the backs of the eyes made visible through | | | | slight tendency for this trait to be shared by close |
| an ophthalmoscope. Of course, if the patient is drowsy | | | | relatives. The 10-year risk for subarachnoid |
| or confused, this might suggest that something serious | | | | hemorrhage in first-degree relatives (parents, siblings |
| is going on, as would any new impairment in the ability | | | | and children) was 1.2%. The risk was even lower in |
| to move the eyes, an arm or a leg. A computed | | | | more distant relatives. In families with two affected |
| tomographic (CT) scan of the head performed within | | | | first-degree relatives there was a trend toward higher |
| the first 24 hours is very sensitive in detecting a | | | | risk. The authors felt that most relatives of patients |
| hemorrhage, but if the scan is delayed it is less able to | | | | suffering subarachnoid hemorrhages have low risk of |
| detect the bleed. A lumbar puncture (also known as a | | | | future hemorrhages, and that routine screening of |
| spinal tap) always detects subarachnoid hemorrhage | | | | family members is inappropriate unless there are |
| even when it is a few days old, but if the needle | | | | multiple affected individuals in the same family. |