[1] Univ Uppsala Hosp, Neurosurg Sect, Dept Neurosci, S-75185 Uppsala, Sweden
[2] Newcastle Gen Hosp, Newcastle Upon Tyne NE4 6BE, Tyne & Wear, England
[3] Osped San Gerardo, Dept Anaesthesia, Monza, Italy
[4] S Glasgow Univ Hosp NHS Trust, Dept Neurosurg, Glasgow, Lanark, Scotland
[5] Virchow Hosp, Charite, Dept Neurosurg, Berlin, Germany
[6] Kaunas Univ Technol, Dept Bioengn, Kaunas, Lithuania
[7] Vall Hebron Univ Hosp, Dept Neurosurg, Barcelona, Spain
[8] Western Gen Hosp, Edinburgh EH4 2XU, Midlothian, Scotland
[9] Baylor Coll Med, Dept Neurosurg, Houston, TX 77030 USA
[10] S Glasgow Univ Hosp NHS Trust, Dept Clin Phys, Glasgow, Lanark, Scotland