1. Division of Artificial Organs, Department of Surgery, University of Western Ontario, London, Ontario, Canada
2. Division of Artificial Organs, University of Western Ontario, London, Ontario, Canada
3. Department of Neurosurgery, University of Western Ontario, London, Ontario, Canada
4. College of Physicians and Surgeons of Columbia University, New York, New York; Division of Neurosurgery, University of Western Ontario, London, Ontario, Canada
5. Department of Surgery, University of Utah College of Medicine, Salt Lake City, Utah; and Department of Clinical Neurological Sciences, University of Western Ontario, London, Ontario, Canada