RT Journal Article SR Electronic T1 Hyperdense basilar artery sign JF BMJ Case Reports FD BMJ Publishing Group Ltd SP bcr2015209317 DO 10.1136/bcr-2015-209317 VO 2015 A1 Karim Mahawish YR 2015 UL http://casereports.bmj.com/content/2015/bcr-2015-209317.abstract AB