1. Medical Research Council/University of Cape Town Medical Imaging Research Unit, Department of Human Biology, Faculty of Health Sciences, University of Cape Town, Observatory, Western Cape;
2. Department of Paediatric Neurosurgery, Red Cross Children's Hospital, Rondebosch, Western Cape;
3. Biostatistics Unit, South African Medical Research Council, Tygerberg, Western Cape, South Africa; and
4. Department of Neurological Surgery, University of California San Francisco, California