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Haemosiderin cap sign

Dr MT Niknejad and Dr Andrew Dixon et al.

The haemosiderin cap sign refers to an MR imaging feature in some spinal tumours where a cap of T2 hypointense haemosiderin is above and / or below the tumour due to previous haemorrhage.

It is most often associated with spinal cord ependymomas, being seen in 20-33% of these cases ¹. The sign however may also be seen in hemangioblastomas and paragangliomas and therefore it is suggestive of but not pathognomonic for ependymoma.

References

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1. Koeller KK, Rosenblum RS, Morrison AL. Neoplasms of the spinal cord and filum terminale: radiologic-pathologic correlation. Radiographics. 20 (6): 1721-49. Radiographics (citation) - Pubmed citation
2. Haaga JR, Boll D. CT and MRI of the whole body. Mosby. (2009) ISBN:0323053750. Read it at Google Books - Find it at Amazon