Monday, April 21, 2008

Search challenge 6: strategies

As Martin points out in his comments on search challenge 6, some of the review-level literature on this topic is older than we've seen for some of the other search challenges.

If you enter "ischemic stroke" into the Entrez MeSH Browser, it links you to "Brain Stem Infarctions" - combining a location (the brain stem) with a particular kind of damage (infarction, i.e. tissue death due to lack of oxygen, often due to reduced blood supply). Infarction is one of the potential downstream effects of ischemia, either due to the length and/or the severity of the ischemic event.

Typing "ischemia" into the MeSH Browser lists "Brain Ischemia" as the 6th hit in the terms retrieved, defined in its scope note as
"Localized reduction of blood flow to brain tissue due to arterial obstruction or systemic hypoperfusion. This frequently occurs in conjunction with brain hypoxia (HYPOXIA, BRAIN). Prolonged ischemia is associated with BRAIN INFARCTION."
"Stroke" is also a MeSH term, defined as
"A group of pathological conditions characterized by sudden, non-convulsive loss of neurological function due to BRAIN ISCHEMIA or INTRACRANIAL HEMORRHAGES. Stroke is classified by the type of tissue NECROSIS, such as the anatomic location, vasculature involved, etiology, age of the affected individual, and hemorrhagic vs. non-hemorrhagic nature."
So I tried this search: brain ischemia[majr] AND stroke[majr] AND (etiology[tiab] OR etiology[sh] OR etiologic[tiab] OR cause[tiab] OR causes[tiab])
limited to All Child, and retrieved ~1000 citations.

And narrowing to exclude some of the (arguably, of course) lesser publciation types like this:
brain ischemia[majr] AND stroke[majr] AND (etiology[tiab] OR etiology[sh] OR etiologic[tiab] OR cause[tiab] OR causes[tiab]) NOT (case reports[pt] OR letter[pt] OR comment[pt] OR editorial[pt] OR news[pt])

reduced the retrieval to ~500 citations. I noticed that a number of the first several pages of hits discussed neonatal and infant stroke; for a "real" request, I imagine that I would either know what pediatric age group the requester is interested in, from our reference interview, or would need to get back in touch to see if we should define "pediatric" as all children, infants only, etc. Narrowing to English language narrows the set even further.

A quick Google search also revealed a report from the National Institute of Neurological Disorders and Stroke from 2005, "Recognition and treatment of stroke in children," which includes a section on etiology and risk factors.

UpToDate, for those who have access, also has a nice overview titled "Ischemic stroke in children and young adults: Etiology and clinical features."

Though I excluded case reports from one of the strategies above, this would likely be a question where I would really want to take a close look at the cases reported in the literature as a complement to the more "synthesized" material from the NINDS report, the UpToDate entry, and the review articles -- there are likely instances of ischemic stroke in children that have made their way into the case literature that have not yet entered into the larger case series or other retrospective works that still may be very useful in gaining a broad perspective on why a given child might have developed an ischemic event.

Adding "risk factors" to the etiology portion of the search string might also be useful too, though it does increase the volume of search retrieval.



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