[1] Univ Washington, Dept Anesthesiol & Pain Med, Seattle, WA 98104 USA
[2] Harborview Injury Prevent & Res Ctr, Washington, WA USA
[3] Univ Washington, Dept Pediat, Seattle, WA 98104 USA
[4] Univ Washington, Dept Neurol Surg, Seattle, WA 98104 USA
[5] Univ Washington, Dept Radiol, Seattle, WA 98104 USA
[6] Univ Washington, Dept Surg, Seattle, WA 98104 USA
[7] Univ Washington, Dept Epidemiol, Seattle, WA 98104 USA