Surgical and Endovascular Management of Aneurysms in the Pediatric Age Group

Introduction

Aneurysms are one of the most common vascular anomalies of the central nervous system but are far less common in children than in adults. These structurally abnormal areas of the arterial wall can cause bleeding, compression of adjacent structures, and concomitant loss of neurologic function. The epidemiology, pathophysiology, presentation, and treatment of pediatric intracranial aneurysms have features distinct from those of adults.

Epidemiology and Pathophysiology

The prevalence of unruptured, asymptomatic intracranial aneurysms (across all ages) is estimated at 3.2%, with only 0.5–4.6% of these present in children . Hemorrhage from aneurysms in the pediatric population is also rare, with only 0.6% of all aneurysmal subarachnoid hemorrhage (SAH) occurring in patients younger than 19 years . With a reported total of ∼18,300 SAH cases annually in the United States, this means that there are only about 100 aneurysmal SAH cases each year in children . Intracranial aneurysms are more common in males than females (especially in prepubertal children) in the ratio 2.7:1, with a shift to a female preponderance (similar to adults) in the ratio 3–5:1 in the postpubertal population .

The size and location of aneurysms in children differ when compared to those in adults. Pediatric patients are more likely to harbor aneurysms in the posterior circulation (25% in children vs. 8% in adults) and less likely to have anterior cerebral artery aneurysms (5–10% in children vs. 34% in adults), but the occurrence of internal carotid artery and middle cerebral artery lesions is roughly the same in both children and adults . Children are less likely than adults to have multiple aneurysms and are two to four times more likely to have giant (>2.5 cm) aneurysms .

The pathophysiology of aneurysms in the pediatric population changes with increasing age. Younger children, particularly those younger than 5 years, predominantly have dissecting, fusiform aneurysms, whereas older children have a majority of saccular aneurysms . Hereditary aneurysms are very rare, accounting for 5–20% of all reported cases in children and young adults, but less than 5% of prepubertal cases . The causes of pediatric intracranial aneurysm are summarized in Table 157.1 .

Presentation and Evaluation

Most aneurysms are asymptomatic and often never detected. There are no formal screening guidelines for children with affected family members, with the exception of some rare genetic disorders, including hereditary hemorrhagic telangiectasia (HHT) . Generally, only family members of sibling pairs or three first-degree relatives who harbor known intracranial aneurysms are recommended for screening, usually with magnetic resonance imaging (MRI)/magnetic resonance angiography (MRA) .

Table 157.2 outlines the common presentations of symptomatic aneurysms. In one series, over half of the pediatric patients with aneurysm presented with SAH—33% presented with mass effect symptoms and in 11% the aneurysm was found after trauma . Children with SAH from aneurysm often present with a lower Hunt–Hess grade than adults, usually 1–3 ( Table 157.3 ).

Evaluation of a patient with a suspected SAH from an aneurysm includes history taking, neurologic and physical examination, and performing radiographic studies to define the anatomy of the lesion. Up to 90% of all nontraumatic SAH in children will result from a structural lesion . These patients should be screened with computed tomographic (CT) scan and if a vascular lesion is suspected, a CT arteriogram (CTA) can be a means of identifying the presence of an aneurysm . Although CTA lacks the details provided by a catheter-based arteriogram, it provides an immediate image outlining the key anatomy of a lesion, which is an information of critical importance in the setting of an acutely ill child. Patterns of SAH in pediatric aneurysm CT studies are summarized in Table 157.4 ( Fig. 157.1 ).

MRI is also useful in the diagnosis and delineation of the three-dimensional anatomy of an aneurysm, particularly with MRA. Overall, MRI/MRA was able to identify the source of SAH correctly in 66% of cases . In contrast, use of catheter-based digital subtraction angiography (DSA)—the gold standard for imaging in aneurysm—was able to identify lesions in 97% of patients, versus 80% of the time without DSA . Angiography generally includes bilateral injection of both the internal and external carotid arteries and the vertebral arteries to visualize all the vessels. Three-dimensional angiography with computer-generated reconstruction is increasingly used to depict the anatomy of lesions ( Fig. 157.2 ). With catheter angiography, an analysis of 241 consecutive pediatric patients revealed a 0% complication rate during the procedure and a 0.4% postprocedural complication rate . Evaluation should look for the following:

• lesion size, orientation, and location

• neck anatomy

• daughter blisters

• other aneurysms (especially important with infectious lesions).

If the aneurysm is fusiform the segment of vessel involved, delineation of normal borders, and involvement of perforators are important.

Standard preoperative laboratory studies, such as complete blood count (CBC), clotting times [prothrombin time (PT)/partial thromboplastin time (PTT)], type and cross (T&C) for blood bank, and a chemistry panel (Chem 7), should be considered as pretreatment studies for aneurysms.