Incidence and Prevalence
- Rare condition: Pediatric aneurysms are rare and account for less than 5% of cases in studies including more than 1,000 aneurysm patients (51, 56).
- Incidental aneurysms: No incidental aneurysms were found in a large autopsy study of 3,000 children younger than 12 years (27). Moreover, no incidental aneurysms were found in two studies analyzing incidental MRI findings in 225 and 120 neurologically healthy children (34, 59).
- Unclear age distribution: Some authors reported a bimodal distribution of symptomatic aneurysms, with a first peak around the second year of life and a second peak in adolescence (7). However, others found an even distribution across the ages of childhood and adolescence (60).
- Near equal gender distribution: 60% of children diagnosed with aneurysms are male. This sex predilection changes gradually after puberty to the adult gender prevalence, i.e., women having a threefold to fivefold increased risk of developing an intracranial aneurysm compared to men (28).
- No geographic variation apparent: This author found no published reports about geographic distribution of pediatric aneurysms. Of note, in a large series of aneurysm patients from Finland, which is known to be a country with a threefold increased incidence of subarachnoid hemorrhage, children accounted for 1.3% of patients (36, 41). This proportion is comparable to series from other geographical regions, although no true comparisons of regional incidences exist. However, geographical differences in the distribution of head trauma and infectious diseases probably influence the occurrence of traumatic and mycotic aneurysms in certain regions to some degree.
- Distinct risk factors compared to adults: The classical modifiable risk factors (such as smoking) are not normally encountered in children. A higher risk of developing a traumatic aneurysm has been described in children, predominantly after closed head injury (2). Similarly, a higher incidence of infectious aneurysms is observed in children. The origin of these aneurysms is mainly bacterial infection, either by direct involvement of intracranial arteries due to sinus or mastoid air cell infections or by infectious embolization. The latter might complicate endocarditis occurring in children with congenital or rheumatic heart disease (2).
Relationships to Other Disease States and Syndromes
A defined underlying condition can be identified in less than 50% of children presenting with an intracranial aneurysm. The following conditions appear to carry an increased risk:
- Renal disorders: Patients with polycystic kidney disease especially appear to be at risk of developing intracranial aneurysms (40).
- Cardiovascular disorders: Coarctation of the aorta increases the risk of intracranial aneurysms (11).
- Hematological, inflammatory, and autoimmune disorders: Intracranial aneurysms are more common in children with sickle-cell anemia (52). Systemic vasculitic syndromes, such as Kawasaki syndrome and Takayasu disease, can also lead to formation of intracranial aneurysms (4, 45).
- Phakomatoses: Tuberous sclerosis complex and NF1 appear to be associated with intracranial aneurysms (3, 28).
- Heritable connective tissue disorders: Cerebral aneurysms are reported to occur in children with Ehlers-Danlos and Marfan syndromes (21, 63).
- Infection: Children with congenital or rheumatic heart disease are at increased risk of bacterial endocarditis, which can lead to mycotic intracranial aneurysms (53).