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