Cerebral aneurysms are a weakness in the blood vessel’s wall that leads to a small focal dilation.  The etiology is debated, but they most probably start as a congenital wall weakness and later enlarge and dilate; changing size and morphology as we age.  The true prevalence of aneurysms in the general population is difficult to predict, but a reasonable estimate is ~5%.  15-20% of patients with an aneurysm will actually have multiple aneurysms.  Risk factors over time for aneurysmal enlargement include older age, smoking, hypertension, atherosclerosis, amphetamine use, head injury, heavy alcohol consumption, blood infections, and low estrogen after menopause.  Congenital risk factors include connective tissue disorders, polycystic kidney disease, coarctation of the aorta, and family history of aneurysms.  Aneurysms also have been found to occur in predictable locations such as branches off blood vessels.  Anterior communicating artery and posterior communicating artery aneurysms are the most common.

Aneurysms may either be identified after rupture (usually presenting as a subarachnoid hemorrhage or intracerebral hemorrhage), after surveillance imaging for a new neurologic deficit or headaches, or incidentally on imaging for an unrelated issue.  Ruptured aneurysms are the most common cause of spontaneous subarachnoid hemorrhage.  Usually the aneurysm temporarily thromboses following the initial bleed, however re-hemorrhage may occur.  The initial treatment for subarachnoid hemorrhage is to stabilize the patient in an intensive care unit followed by surgical treatment of the aneurysm.

A noncontrast computed tomography (CT) scan is useful in determining if a subarachnoid hemorrhage has occurred and may identify larger aneurysms.  If the clinical findings suggest a bleed but the CT scan appears negative, a lumbar puncture may be performed to identify red blood cells or xanthrochromia in the cerebral spinal fluid.  If an aneurysm is suspected, ruptured or unruptured, a CT angiogram or magnetic resonance angiogram are also useful tests to identify possible intracranial aneurysms.  However a dedicated four vessel cerebral angiogram is the gold standard for diagnosis.

Great debate exists as to the treatment of unruptured cerebral aneurysms.  As a result there have been a number of efforts to determine the natural history of aneurysms in relation to morbidity and mortality, patient age, aneurysm size, and aneurysm location.  The International Study of Unruptured Intracranial Aneurysms (ISUIA) was a two part study attempting to evaluate these issues.  Based on size and location, aneurysms smaller than 7mm appear to have a very low risk of rupture and it is not until they are larger than ~13mm that significant risk or rupture exists, unless the aneurysm is in the posterior circulation.  If the aneurysm is a posterior communicating artery aneurysm or in the posterior circulation, aneurysms larger than 7mm pose a fairly significant risk of rupture.  Of course these are not steadfast rules.  Any aneurysm may rupture at any time, and patients should be counseled regarding their specific risk factors for rupture and desire for prophylactic surgery.  A young patient with a 3mm aneurysm who is a smoker has a different risk profile to an older healthy patient with same size aneurysm.  Any patient with an aneurysm should be evaluated by a neurosurgeon.

There have been no identified conservative management strategies for aneurysm treatment other than changing modifiable risk factors.  Surgery is the only definitive treatment.  Surgery may be performed as an open procedure where a metal clip is placed on the aneurysm or as an endovascular procedure where small metal coils are placed inside the aneurysm.  In either strategy, the aneurysm dome is blocked so that blood cannot enter and the vessel wall repairs with time.  There are advantages and disadvantages to either procedure.  A large study called the International Subarachnoid Aneurysm Trial (ISAT) was reported in 2002 to compare the two treatments.  It appears that either treatment may successfully treat aneurysms.  However, the aneurysm location, morphology, and patient preference are the key features that should determine whether an aneurysm is microsurgically clipped or endovascularily coiled.

For and evaluation please call The Neurosurgery Center of Colorado at 303-481-0035 and make an appointment with Adam P. Smith, MD.