[1] Western Gen Hosp, Dept Clin Neurosci, Edinburgh EH4 2XU, Midlothian, Scotland
[2] Ullevaal Univ Hosp, Dept Internal Med, Oslo, Norway
[3] Scripps Res Inst, Dept Mol & Expt Med, La Jolla, CA USA
[4] Natl Cardiovasc Ctr, Cerebrovasc Div, Suita, Osaka 565, Japan