Diagnosis of a ruptured cerebral aneurysm is commonly made by finding signs of subarachnoid hemorrhage on a CT scan (Computerized Tomography, sometimes called a CAT scan). The CT scan is a computerized test that rapidly X-rays the body in cross-sections, or slices, as the body is moved through a large, circular machine. If the CT scan is negative but a ruptured aneurysm is still suspected, a lumbar puncture is performed to detect blood in the cerebrospinal fluid (CSF) that surrounds the brain and spinal cord.
To determine the exact location, size and shape of an aneurysm (ruptured or unruptured), neuroradiologists will use either cerebral angiography or tomographic angiography.
Cerebral angiography, the traditional method, involves introducing a catheter (small plastic tube) into an artery (usually in the leg) and steering it through the blood vessels of the body to the artery involved by the aneurysm. A special dye, called a contrast agent, is injected into the patient's artery and its distribution is shown on X-ray projections. This method may not detect some aneurysms due to overlapping structures or spasm.
Computed Tomographic Angiography (CTA) is an alternative to the traditional method and can be performed without the need for arterial catheterization. This test combines a regular CT scan with a contrast dye injected into a vein. Once the dye is injected into a vein, it travels to the brain arteries, and images are created using a CT scan. These images show exactly how blood flows into the brain arteries.
A false- or pseudoaneurysm does not primarily involve such distortion of the vessel. It is a collection of blood leaking completely out of an artery or vein, but confined next to the vessel by the surrounding tissue. This blood-filled cavity will eventually either thrombose (clot) enough to seal the leak or it will rupture out of the tougher tissue enclosing it and flow freely between layers of other tissues or into looser tissues. Pseudoaneurysms can be caused by trauma that punctures the artery and are a known complication of percutaneous arterial procedures such as arteriography or of arterial grafting or of use of an artery for injection, such as by drug abusers unable to find a usable vein. Like true aneurysms they may be felt as an abnormal pulsatile mass on palpation.
Blood clots from popliteal arterial aneurysms can travel downstream and suffocate tissue. Only if the resulting pain and/or numbness are ignored over a significant period of time will such extreme results as amputation be needed. As long as treatment is sought quickly, a doctor should be able to provide non-invasive treatment. Aneurysms should be treated with care as over pressure when trying to get rid of them can cause them to shift. Clotting in popliteal venous aneurysms are much more serious as the clot can embolise and travel to the heart, or through the heart to the lungs (a pulmonary embolism). Risk factors for an aneurysm are diabetes, obesity, hypertension, tobacco use, alcoholism, and copper deficiency.
A minority of aneurysms are caused by a copper deficiency. Numerous animal experiments have shown that a copper deficiency can cause diseases affected by elastin tissue strength [Harris]. The lysyl oxidase that cross links connective tissue is secreted normally, but its activity is reduced, due, no doubt, to some of the initial enzyme molecules (apo-enzyme or enzyme without the copper) failing to contain copper.
Aneurysms of the aorta are the chief cause of death of copper deficient chickens, and also depleting copper produces aneurysms in turkeys.
Men who die of aneurysms have a liver content which can be as little as 26% of normal. The median layer of the blood vessel (where the elastin is) is thinner but its elastin copper content is the same as normal men. The overall thickness is not different. The body must therefore have some way of preventing elastin tissue from growing if there is not enough activated lysyl oxidase for it. Men are more susceptible to aneurysms than young women, probably because estrogen increases the efficiency of absorption of copper. However, women can be affected by some of these problems after pregnancy, probably because women must give the liver of their babies large copper stores in order for them to survive the low levels of copper in milk. A baby’s liver has up to ten times as much copper as adult livers. Elastin is about as flexible as a rubber band and can stretch to two times its length. Collagen is about 1000 times stiffer.
A healthy artery can resist blood pressure of up to about 1,000 mm Hg before rupturing. Therefore keeping strength of arteries up would seem to be even more important than keeping blood pressure down.
Aneurysm formation is probably the result of multiple factors affecting that arterial segment and its local environment.
Hemodynamically, the coupling of aneurysmal dilation and increased wall stress is approximated by the law of Laplace. Specifically, the Laplace law states that the (arterial) wall tension is proportional to the pressure times the radius of the arterial conduit (T = P X R). As diameter increases, wall tension increases, which contributes to increasing diameter. As tension increases, risk of rupture increases. Increased pressure (systemic hypertension) and increased aneurysm size aggravate wall tension and therefore increase the risk of rupture. In addition, the vessel wall is supplied by the blood within its lumen in humans. Therefore in a developing aneurysm, the most ischemic portion of the aneurysm is at the farthest end, resulting in weakening of the vessel wall there and aiding further expansion of the aneurysm. Thus eventually all aneurysms will, if left to complete their evolution, rupture without intervention. In dogs, collateral vessels supply the vessel and aneurysms are rare.
At this point it appears that the risks associated with surgical clipping and endovascular coiling, in terms of stroke or death from the procedure, are the same. The major problem associated with endovascular coiling, however, is the high recurrence rate and subsequent bleeding of the aneurysms. For instance, the most recent study by Jacques Moret and colleagues from Paris, France, (a group with one of the largest experiences in endovascular coiling) indicates that 28.6% of aneurysms recurred within one year of coiling, and that the recurrence rate increased with time. (Piotin M et al., Radiology 243(2):500-508, May 2007) These results are similar to those previously reported by other endovascular groups. For instance Jean Raymond and colleagues from Montreal, Canada, (another group with a large experience in endovascular coiling) reported that 33.6% of aneurysms recurred within one year of coiling. (Raymond J et al., Stroke 34(6):1398-1403, June 2003) The long-term coiling results of one of the two prospective, randomized studies comparing surgical clipping versus endovascular coiling, namely the International Subarachnoid Aneurysm Trial (ISAT) are turning out to be similarly worrisome. In ISAT, the need for late retreatment of aneurysms was 6.9 times more likely for endovascular coiling as compared to surgical clipping. (Campi A et al., Stroke 38(5):1538-1544, May 2007)
Therefore it appears that although endovascular coiling is associated with a shorter recovery period as compared to surgical clipping, it is also associated with a significantly higher recurrence and bleeding rate after treatment. Patients who undergo endovascular coiling need to have annual studies (such as MRI/MRA, CTA, or angiography) indefinitely to detect early recurrences. If a recurrence is identified, the aneurysm needs to be retreated with either surgery or further coiling. The risks associated with surgical clipping of previously-coiled aneurysms are very high. Ultimately, the decision to treat with surgical clipping versus endovascular coiling should be made by a cerebrovascular team with extensive experience in both modalities. At present it appears that only older patients with aneurysms that are difficult to reach surgically are more likely to benefit from endovascular coiling. These generalizations, however, are difficult to apply to every case, which is reflected in the wide variability internationally in the use of surgical clipping versus endovascular coiling.