Intracranial aneurysms are common disorders, occurring in approximately 2 percent of the general population. They can be either asymptomatic or symptomatic, presenting acutely with a subarachnoid or intracerebral hemorrhage. When an aneurysm ruptures, it is fatal in approximately 40 percent of patients.
Because of this high potential mortality, expert, immediate and comprehensive aneurysm management is a medical imperative. Fredric B. Meyer, M.D., a neurosurgeon at Mayo Clinic in Rochester, Minn. explains, "If a patient survives the initial hemorrhage, the optimal outcome is obtained through a multispecialty approach that commences in the emergency department and extends through the time of treatment of the lesion, subsequent management in the intensive care unit and then recovery in a rehabilitation unit if necessary."
Dr. Meyer adds that optimal outcomes of all aneurysm cases — not just ruptures — are best achieved through an advanced multidisciplinary team approach.
Among the larger referral practices for the treatment of aneurysm in North America, Mayo Clinic neurosciences physicians manage all manifestations of this complex clinical presentation. Team members have special expertise and extensive experience treating all forms, especially skull base, posterior circulation and giant aneurysms. They can quickly apply the most effective and least invasive treatment.
The severity of the health threat depends on many variables, including size, location, patient age, and prior neurologic history. "Hence, there are differences between small, asymptomatic aneurysms in the anterior circulation compared with similar-sized aneurysms in the posterior circulation or large, complex giant aneurysms," Dr. Meyer says. "Accordingly, not all aneurysms necessarily require treatment. Furthermore, the risks of intervention must be balanced against the predicted natural history of the aneurysm if left untreated."
When a patient is referred to the Mayo Clinic Cerebrovascular Clinic for treatment of an intracranial aneurysm, the first step is to carefully consider whether to treat or observe the aneurysm.
Therefore, the decision to treat also must take into account patient age, the presence of comorbid conditions, and neurologic function. Sometimes, the safer approach is observation, with control of hypertension if present, smoking cessation if the patient is a smoker and intermittent repeat imaging to be sure the aneurysm is not changing.
In direct surgical repair with the patient under general anesthesia, the aneurysm is approached through a craniotomy. The advantages of the surgical approach are that the surgeon can visualize the aneurysm and treatment is most often definitive and curative. The disadvantages are that surgery is invasive, carries the risks of any invasive procedure and requires three to five days of recovery time in the hospital.
Coil embolization is performed by an interventional team. A catheter is passed through the femoral artery into the cerebral circulation and wire coils are inserted into the aneurysm, detached from the supporting wire left in place after proper positioning is carefully checked under radiographic control. Sometimes balloons or stents are used with the coils.
The advantage of endovascular treatment is that it is less invasive than direct surgery and therefore generally better tolerated by patients. "Endovascular treatment is rapidly gaining ground as a valid alternative to open surgery in an increasing number of patients with intracranial aneurysms," observes Giuseppe Lanzino, M.D., a neurosurgeon at Mayo Clinic in Rochester, Minnesota. Dr. Lanzino has dual subspecialty training in endovascular and open vascular neurosurgery.
A disadvantage of endovascular treatment is that the aneurysm may not be obliterated completely and repeated imaging follow-up may be required. At Mayo Clinic, all patients who undergo endovascular aneurysm occlusion procedures are followed at regular intervals to ensure that there is no recurrence.
Some complex aneurysms are difficult to treat and require advanced surgical and endovascular skills. In addition to size, these lesions often have broad necks that incorporate the origin of perforators or major blood vessels. Sometimes these aneurysms are dolichoectatic, a term used to describe giant fusiform aneurysms of a major blood vessel, most commonly the internal carotid, middle cerebral, basilar, or posterior cerebral arteries. Direct occlusion of a fusiform aneurysm by default would cause loss of the parent blood vessel.
In these circumstances, straightforward clipping or endovascular occlusion is often not an option because of the risk of stroke. Intervention often requires advanced techniques such as intracranial vascular reconstruction using microsurgical techniques, bypass surgery, or resection of the aneurysm under deep hypothermia.
A final alternative is a combined interventional surgical approach in which an intracranial bypass graft is constructed first, followed by endovascular proximal vessel occlusion or embolization.
"Patients who undergo treatment for aneurysms that have hemorrhaged or for complex aneurysms often require special care in the neurology intensive care unit. Patients are aggressively treated to avoid potential sequelae of aneurysmal subarachnoid hemorrhage, including hydrocephalus, vasospasm, and cardiopulmonary complications," Dr. Meyer explains.
After recovery, all patients are seen in the Cerebrovascular Clinic to make sure they have no delayed complications. For incompletely obliterated aneurysms, a follow-up plan is developed to watch for possible aneurysm regrowth.