[1] Newcastle Gen Hosp, STICH, Newcastle Upon Tyne NE4 6BE, Tyne & Wear, England
[2] So Gen Hosp, Univ Dept Neurosurg, Glasgow G51 4TF, Lanark, Scotland
[3] Newcastle Gen Hosp, Dept Geriatr, Newcastle Upon Tyne NE4 6BE, Tyne & Wear, England
[4] Addenbrookes Hosp, Acad Neurosurg Unit, Cambridge, England
[5] Univ Edinburgh, Dept Community Hlth Sci, Edinburgh, Midlothian, Scotland