RT Journal Article SR Electronic T1 Thunderclap headache JF Practical Neurology JO Pract Neurol FD BMJ Publishing Group Ltd SP 294 OP 297 DO 10.1136/jnnp.2009.188037 VO 9 IS 5 A1 Niraj Mistry A1 Liberty Mathew A1 Allyson Parry YR 2009 UL http://pn.bmj.com/content/9/5/294.abstract AB