[1] Univ St Andrews, Sch Biol, St Andrews KY16 9TS, Fife, Scotland
[2] Univ St Andrews, Sch Med, St Andrews KY16 9TS, Fife, Scotland
[3] Columbia Univ, Coll Phys & Surg, Dept Pathol, New York, NY 10032 USA
[4] Columbia Univ, Coll Phys & Surg, Dept Surg, New York, NY 10032 USA
[5] N Shore Long Isl Jewish Hlth Syst, Harvey Cushing Inst Neurosci, Great Neck, NY 11021 USA