Inverted Napoleon hat sign
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At the time the article was created Frank Gaillard had no recorded disclosures.View Frank Gaillard's current disclosures
At the time the article was last revised Matt A. Morgan had no recorded disclosures.View Matt A. Morgan's current disclosures
The inverted Napoleon hat sign is a radiologic sign seen on the frontal pelvic or lumbar radiograph at the level of the 5th lumbar vertebra and the sacrum.
It is seen when there is bilateral spondylolysis with marked anterolisthesis of L5 on S1 or marked exaggeration of the normal lordosis at the lumbosacral junction. Spondylolysis resulting in this degree of spondylolisthesis is more often congenital and/or traumatic in origin and less often degenerative.
The "brim" of hat is formed by the caudal translation of the transverse processes and the "dome" of hat is formed by the body of L5.
- 1. Talangbayan LE. The inverted Napoleon's hat sign. Radiology. 2007;243 (2): 603-4. doi:10.1148/radiol.2432030499 - Pubmed citation