RT Journal Article SR Electronic JF Journal of Neurology, Neurosurgery & Psychiatry JO J Neurol Neurosurg Psychiatry FD BMJ Publishing Group Ltd SP 421 OP 421 DO 10.1136/jnnp.64.3.421b VO 64 IS 3 YR 1998 UL http://jnnp.bmj.com/content/64/3/421.3.abstract AB