[1] Addenbrookes Hosp, Dept Clin Neurosci, Neurosurg Unit, Cambridge, England
[2] Univ Heidelberg, Dept Neurol, Heidelberg, Germany
[3] Western Sussex Hosp NHS Trust, Dept Anaesthet & Intens Care, Worthing, W Sussex, England
[4] Wroclaw Univ Technol, Inst Biomed Engn & Instrumentat, PL-50370 Wroclaw, Poland