Perineural Spread – Summary
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I do want to make one point about perineural
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spread of malignancies.
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Although adenoid cystic carcinoma,
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of all the malignancies,
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has the highest rate of perineural spread,
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that is 50% to 60%,
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the most common tumor associated with perineural spread
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is squamous cell carcinoma. And why is that?
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It's because the prevalence of squamous cell carcinoma
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is so much higher than adenoid cystic carcinoma.
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We see squamous cell carcinoma throughout
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the aerodigestive system.
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And although it has a lower rate of spread just
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by virtue of its much higher frequency,
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it is the tumor that has the highest
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rate of perineural spread.
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Besides squamous cell and adenoid cystic carcinoma,
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lymphoma also may spread up the cranial
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nerves via perineural spread.
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When I speak about squamous cell carcinoma,
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I also should talk about skin cancers.
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And it's true that squamous cell carcinoma of the skin as
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well as, to a lesser extent, basal cell and melanoma both,
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all three of them have a small rate of perineural spread
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in the skin, and that can lead to deep invasion.
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Remember that for perineural spread on CT scan.
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Generally,
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what we're looking for is bony destruction
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of the foramina at the skull base,
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because we usually are not able to actually
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see the nerve itself that well.
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Nor can we see contrast enhancement of the nerves
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that well on CT. With MRI scanning, however,
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we do see thick nerves, we see enhanced nerves,
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and we also may see the bony destruction and foraminal
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widening, which may also be present on CT scanning.
David M Yousem, MD, MBA
Professor of Radiology, Vice Chairman and Associate Dean
Johns Hopkins University
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