[1] Newcastle Univ, Neurosurg Trials Unit, Newcastle Upon Tyne NE2 4AE, Tyne & Wear, England
[2] Heidelberg Univ, Dept Neurosurg, D-69120 Heidelberg, Germany
[3] Newcastle CTU, Sch Med, Inst Hlth & Soc, Newcastle Upon Tyne NE2 4HH, Tyne & Wear, England
[4] James Cook Univ Hosp, Middlesbrough TS4 3BW, Cleveland, England
[5] Univ Aberdeen, Hlth Econ Res Unit, Inst Appl Hlth Sci, Aberdeen AB25 2ZD, Scotland