[1] Columbia Univ, New York, NY USA
[2] Columbia Univ, Dept Neurol, New York, NY USA
[3] Columbia Univ, Dept Obstet & Gynecol, New York, NY USA
[4] Columbia Univ, Sergievsky Ctr, New York, NY USA
[5] New York State Dept Hlth, Off Qual & Patient Safety, New York, NY USA
[6] Columbia Univ Coll Phys & Surg, Dept Neurol, New York, NY 10032 USA