1. School of Medicine (Neural Tissue Engineering Keele Group), Faculty of Medicine and Health Sciences, David Weatherall Building, Keele University, Newcastle-Under-Lyme, Staffordshire ST55BG, U.K.
2. Department of Neurosurgery, Royal Stoke University Hospital, Newcastle Road, Stoke-on-Trent ST4 6QG, U.K.
3. School of Life Sciences (Neural Tissue Engineering Keele Group), Huxley Building, Keele University, Newcastle-Under-Lyme, Staffordshire ST55BG, U.K.