1. Department of Medicine (G.P.-W., P.U.F., T.P.J., K.M., S.L.W.), New York, New York 10032
2. Department of Radiology (A.G.K.), New York, New York 10032
3. Department of Neurological Surgery (J.N.B.), Columbia University College of Physicians & Surgeons, New York, New York 10032
4. Department of Medicine (S.T.F.), Mt Sinai/St Luke's Roosevelt Hospital, New York, New York 10019
5. Faculties of Life Sciences and Medical and Human Sciences (A.W.), University of Manchester, Manchester M13 9PT, United Kingdom