Rule of 5: angiographic diameters of cervicocerebral arteries in children and compatibility with adult neurointerventional devices

Background and purpose The safety of using adult-sized neuroendovascular devices in the smaller pediatric vasculature is not known. In this study we measure vessel diameters in the cervical and cranial circulation in children to characterize when adult-approved devices might be compatible in children. Methods For 54 children without vasculopathy (mean age 9.5±4.9 years (range 0.02–17.8), 20F/34M) undergoing catheter angiography, the diameters of the large vessels in the cervical and cranial circulation (10 locations, 611 total measurements) were assessed by three radiologists. Mean±SD diameter was calculated for the following age groups: 0–6 months, 1, 2, 3, 4, 5–9, 10–14, and 15–18 years. To compare with adult sizes, each vessel measurement was normalized to the respective region mean diameter in the oldest age group (15–18 years). Normalized measurements were compared with age and fitted to a segmented regression. Results Vessel diameters increased rapidly from 0 to 5 years of age (slope=0.069/year) but changed minimally beyond that (slope=0.005/year) (R 2 =0.2). The regression model calculated that, at 5 years of age, vessels would be 94% of the diameter of the oldest age group (compared with 59% at birth). In addition, most vessels in children under 5, while smaller, were still potentially large enough to be compatible with many adult devices. Conclusions The growth curve of the cervicocerebral vasculature displays rapid growth until age 5, at which point most children's vessels are nearly adult size. By age 5, most neuroendovascular devices are size-compatible, including thrombectomy devices for stroke. Under 5 years of age, some devices might still be compatible.