Brain aneurysms are sometimes found incidentally in patients who have imaging scans for another reason. The questions that come immediately to the patient's and doctor's mind are
Are these patients at high risk of subarachnoid hemorrhage?
When should they see a stroke specialist, and should incidental aneurysms always be treated?
What is the risk of an unruptured brain aneurysm?
Rupture risk assessment is complex and depends on many factors. When an aneurysm is found incidentally, it is recommended that the patient consult a Vascular Neurosurgeon for evaluation and discussion of risk and treatment options.
While there is no concrete data from literature, 7 mm is generally considered the outer limit of a “small” aneurysm.Lesions smaller than 7 mm carry between 0.5 to 5 percent risk of rupture in the next five years, while a 12-mm aneurysm has a risk as high as 12 percent and a 25-mm lesion, 50 percent.
Aneurysms located on certain arteries carry more risk of rupture than others. Those located on the anterior communicating artery, posterior communicating artery and the posterior circulation i.e., vertebro-basilar system have a higher risk of rupture than those located elsewhere. Aneurysms with certain morphologic features, such as those containing “daughter sac" may have higher risk over time. Finally, 20 to 30 percent of patients with aneurysms have more than one lesion. This increases rupture risk, especially if one has ruptured previously.
How common are unruptured Brain Aneurysms?
Approximately 3 percent of the population has unruptured intracranial aneurysms. Most are asymptomatic. Patients with severe, sudden, acute-onset headache, often described as “the worst headache of my life,” may have a ruptured aneurysm, especially if they also have stiff neck, nausea, vomiting and syncope. These patients should go to the emergency department immediately.
Patients who recently had severe headache and stiff neck but did not seek treatment may have had a sentinel subarachnoid hemorrhage.These patients have 50 percent risk of a second, potentially fatal hemorrhage in the next 30 days. These patients should also go to the emergency department immediately.
Unruptured aneurysms should also be suspected in patients with:
Unusually severe headache with acute onset, including associated with sexual activity
Drooping of one eyelid
Blurred or double vision
Should patients be screened?
The incidence of harboring a brain aneurysm is about 9% in patients who have two or more one first-degree relative with an aneurysm, and these patients should be screened for aneurysms with magnetic resonance angiography or CT angiography. Patients with certain genetic diseases such as autosomal dominant polycystic kidney disease should also be screened.
Should unruptured Brain Aneurysms be treated?
The question of whether and when to treat an unruptured brain aneurysm is highly individualized and depends on a number of patient and aneurysm factors.
Observation or Watchful Waiting
Patients whose aneurysms are not treated but observed, should have good blood pressure control and stop smoking, if they smoke. Excessive alcohol consumption should also be avoided, although there is no evidence in this regard. These lifestyle changes decrease the risk of developing an aneurysm, rupture and treatment complications.
Patients with small, asymptomatic aneurysms should be screened with magnetic resonance angiography, with repeat screening in a year. If the aneurysm is stable, they can be followed up with serial MRAs at two and three years. If an aneurysm grows or changes shape or the patient exhibits mass effects or cranial nerve symptoms, the risk goes up and such an aneurysm should be considered for treatment.
Endovascular coiling and Surgery
The main interventions for an unruptured aneurysm are surgical clipping and endovascular coiling or flow diversion. Risk of treatment depends on aneurysm complexity, patient health and other factors. The decision for surgical clipping or endovascular therapy should be discussed with the patient by an experienced vascular neurosurgery team. Depending upon the nature of the aneurysm and experience of the treating vascular neurosurgeon, surgical clipping and endovascular therapy should be chosen.
The usual duration of stay for a patient with unruptured brain aneurysm undergoing surgery at our center is 8 days whereas that for a patient undergoing endovascular therapy is about 3-4 days.