S Cheriyan1, S Santoreneos2, A J Wells3. 1. Department of Neurosurgery, Royal Adelaide Hospital, South Australia, Australia. Electronic address: Sanith.Cheriyan@sa.gov.au. 2. Department of Neurosurgery, Royal Adelaide Hospital, South Australia, Australia. 3. Department of Neurosurgery, Royal Adelaide Hospital, South Australia, Australia; The University of Adelaide, South Australia, Australia.