OVERVIEW: What every practitioner needs to know

Are you sure your patient has had an aneurysm? What are the typical findings for this condition?

Most pediatric aneurysms are symptomatic and children can present with headache, focal neurologic deficits, seizures, and subarachnoid hemorrhage (SAH) secondary to rupture.

What caused this disease to develop at this time?

Adult aneurysms have strong risk factors (e.g., hypertension, cigarette smoking, drug abuse) that are not typically present in the pediatric population. There is no underlying distinct pathogenesis for pediatric aneurysms.

For the pediatric population, trauma, infection, and inflammation appear to be causative factors for aneurysm formation. There also appears to be a role for defective defensive mechanisms such as improper self-repair of a vessel wall, vessel wall matrix disorders, and certain genetic vascular diseases that increase the likelihood of aneurysm formation in the pediatric population.

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Would imaging studies be helpful? If so, which ones?

Noncontrast head computed tomography (CT) is typically the first imaging study performed and can quickly determine if a SAH is present. To further characterize the location, size, and morphologic features of an aneurysm, an angiographic study will usually be performed. Findings will also guide management options.

Magnetic resonance imaging/magnetic resonance angiography is a valuable tool for examining pediatric patients with unruptured aneurysms who are being followed with regular surveillance after treatment.

Confirming the diagnosis

Approximately 60% of pediatric patients presenting with nontraumatic SAH have a cerebral aneurysm as the underlying cause. Noncontrast head CT is the first diagnostic test for a child with suspected SAH. If the CT study is normal, but suspicion for a SAH is still high based on the clinical history, a lumbar puncture is required.

If a nontraumatic SAH is identified, the next diagnostic study to identify the source of the SAH will be CT angiography, magnetic resonance angiography, or catheter angiography depending on the resources of the institution. Efforts should be made to reduce radiation exposure while obtaining the information needed to plan subsequent management.

If you are able to confirm that the patient has had an aneurysm, what treatment should be initiated?

Treatment options for pediatric patients with aneurysms include conservative management with observation, endovascular therapy, or surgical clipping.

Endovascular therapy involves the use of detachable coils ± stents delivered through microcatheters from a transfemoral catherization. Although less invasive than traditional surgery, the disadvantage of endovascular treatment is that there is a higher incidence of the need for retreatment.

Surgery involves direct clipping of the aneurysm or aneurysm trapping ± bypass procedures. Several retrospective studies have shown that surgery has a higher rate of complete obliteration and a lower rate of recurrence compared with endovascular treatment; however, the surgery is more invasive and has a higher infarction rate.

Treatment planning should be undertaken with a multidisciplinary approach and should consider the aneurysm configuration, surgical risks, treatment durability, and subsequent surveillance.

What are the adverse effects associated with each treatment option?

Current treatment-related complications are low in both endovascular and surgical approaches in comparison with previous reports.

Endovascular treatment has a higher incidence of requiring retreatment, whereas surgery is more invasive and appears to have a higher infarction rate.

What are the possible outcomes of aneurysm?

Aneurysmal disease is considered both an acute and chronic condition, as there is a significant percentage of patients with subsequent recurrence and/or de novo aneurysm development. Pediatric patients warrant close follow-up with regular surveillance imaging.

SAH secondary to a ruptured aneurysm is generally better tolerated by the pediatric population than by adults. There also appears to be a much lower rate of clinically significant vasospasm in pediatric patients with ruptured aneurysms.

What causes this disease and how frequent is it?

Intracranial aneurysms in the pediatric population are exceedingly rare, with less than 5% of aneurysms occurring in patients aged 18 years or younger. Pediatric patients accounted for less than 1% of ruptured aneurysms in one study.

Pediatric aneurysms are believed to have a pathogenesis distinct from that of adult aneurysms. Pediatric aneurysms also differ from adult aneurysms in their male predominance, predilection for the posterior circulation and internal carotid bifurcation, and greater incidence of giant aneurysms.

In one study, the cause of aneurysm in a pediatric population could be found in less than 50% of cases. However, aneurysms can be classified as traumatic, infectious, saccular, and dissecting, with each entity having a distinct pathogenesis and clinical presentation that dictates management.

How do these pathogens/genes/exposures cause the disease?

Traumatic aneurysms constitute 5%-10% of all pediatric intracranial aneurysms. Patients classically present with a delayed SAH 2-4 weeks after the initial traumatic insult. More than 70% of traumatic aneurysms can be attributed to closed head injuries. Injury disrupts the arterial wall, and the subsequent fibrotic reaction produces a false sac (pseudoaneurysm).

Infectious aneurysms constitute approximately 15% of all pediatric intracranial aneurysms.
Staphylococcus aureus, Streptococcus viridans, and gram-negative organisms are the most common organisms found in blood and cerebrospinal fluid cultures. However, in approximately 30% of cases, no infectious agent can be identified.

In large arteries, it appears the infection extends from an adjacent structure toward the lumen, whereas in smaller distal arteries, the infectious process appears to extend from the lumen during septicemia to the extravascular space. These patients typically present with hemorrhage within the first 48 hours.

The classic saccular aneurysm is found in approximately 20% of pediatric intracranial aneurysms and typically affects older patients. The natural history of these aneurysms is similar to the adult form, but the pathogenesis is hypothesized to be due to defective defense mechanisms.

Dissection aneurysms are the most common variant, constituting 50% of all pediatric intracranial aneurysms in some studies. The clinical presentation of a patient with a dissecting aneurysm is variable, with hemorrhagic, ischemic, and/or mass effect symptoms possible, underscoring different pathophysiologic mechanisms involved in each circumstance.

What is the evidence?

Jian, B, Hetts, S, Lawton, M. “Pediatric intracranial aneurysms”. Neurosurg Clin N Am. vol. 21. 2010. pp. 491-501.

Krings, T, Geibprasert, S, terBrugge, K. “Pathomechanisms and treatment of pediatric aneurysms”. Childs Nerv Syst. vol. 26. 2010. pp. 1309-18.