Onyx-18 is a relatively new liquid embolic agent. The initial success with this polymer will result in increased utilization in children, but its use and safety in the pediatric population have not been firmly established.

Between December 2005 and January 2008, the cerebral vascular malformations in 6 children were embolized using Onyx-18. The ages of the patients ranged from 1 day to 12 years. Pathological types of the vascular malformations included 4 arteriovenous malformations and 2 vein of Galen malformations. Clinical presentations included intracranial hemorrhage in 2 patients, papilledema in 1 patient, and high-output heart failure in 3 patients.

In 6 pediatric patients, 21 embolization procedures were performed utilizing a combination of Onyx-18, platinum coils, and Embosphere microspheres. The average estimated size reduction for the arteriovenous malformations was 60%. Total obliteration of a malformation was achieved in 1 patient. Two patients received adjuvant radiosurgery. Of the 2 vein of Galen malformations, one was completely embolized and the other had an ~ 50% reduction in flow. No open surgical intervention was used. Clinical follow-up ranged from 7 to 12 months. Angiographic follow-up data were obtained at 1, 6, and 7 months in 3 patients, whereas 1 patient awaits repeat angiography. Complications included a transient monoparesis with complete resolution in 1 patient. Two patients died within 24 hours of an embolization procedure due to intracranial hemorrhages.

Onyx-18 is a feasible embolization agent for use in intracranial vascular malformations in the pediatric population, but long-term follow-up data will be necessary to assess the continued efficacy and safety of this agent.