To tell the truth, I was hoping that Saq’s enigmatic references to a new toolset would save the day.
Maybe my solution isn’t the right path. But the following would extract the lightbox references from your text:
<$vars regexp="<<lightbox\s+.*?>>(?g)">
<$list filter="[[Cortical laminar necrosis]get[text]regexps<regexp>]">
</$list>
</$vars>
I suspect that learning regular expressions is considerably easier than “Cortical laminar necrosis”.