This 40-year-old female presents with Chiari malformation post decompression with occipital headaches. Why are there still problems? In this instance the foramen magnum has been decompressed. Focus on the first two images, then look at duplicates of the same images with arrows indicating key findings.
Causes for failure of Chiari decompression can include inadequate decompression or pseudomeningocele formation. Another less frequently appreciated cause of recurrent symptoms is the possibility of cerebellar ptosis. The decompression in this case goes above the equator of the cerebellum. This can result in inferior migration and ptosis of the cerebellum with reproduction of obstruction at the foramen magnum. In this instance, there is a subtle impression of the occipital bone on the cerebellum with effacement of the retrocerebellar cerebrospinal fluid spaces which can indicate the development of ptosis. Not only can this result in recurrent headaches, but it can also result in re-expansion of a syrinx if one was present or the development of one. This topic was addressed here.
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