1. From the Department of Neurosurgery (J.S.H., A.J.M., J.A.R., M.Z., E.A.S., D.M.H.), University of Iowa Hospitals and Clinics, Iowa City.
2. Department of Neurology (J.A.R., E.A.S.), University of Iowa Hospitals and Clinics, Iowa City.
3. Department of Radiology (E.A.S.), University of Iowa Hospitals and Clinics, Iowa City.