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Br J Neurosurg. 2014 Jun;28(3):330-4. doi: 10.3109/02688697.2013.841847. Epub 2013 Sep 25.

Foramen magnum decompression for Chiari I malformation: a procedure not to be underestimated.

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  • 1Department of Neurosurgery, Beaumont Hospital , Dublin , Ireland.



Chiari I malformation may be treated with foramen magnum decompression (FMD). We aim to describe the symptoms with which patients initially present, and to determine the number and type of complications occurring after FMD for Chiari I malformation.


Retrospective review of medical records for patients who had FMD performed for Chiari I malformation between January 2009 and December 2011. Post-operative outcomes were recorded and analysed. Patient demographic details and other relevant medical conditions were also noted.


Between January 2009 and December 2011, 54 FMDs were performed for Chiari I malformation. Among them, 40(74%) patients were female and 14 patients (26%) were male. The majority of patients (42.6%) were aged 16-39 years and 24.07% of patients were children aged < 16 years. A total of 30(55.6%) patients had documented evidence of a syrinx pre-operatively. 18(33.3%) patients developed complications. Nine of these developed multiple complications while nine had a single problem. One mortality was reported. Ten (18.5%) patients developed hydrocephalus requiring shunting. Two patients developed subdural collections requiring evacuation associated with hydrocephalus. Six (11.1%) patients developed post-operative infections: two CNS infections; one wound infection; and three other infections.


FMD for Chiari I malformation is a procedure which carries risk. In particular, the risk of developing post-operative hydrocephalus requiring permanent shunting is relatively high. ICP monitoring prior to FMD may be required to definitively rule out raised intracranial pressure.


Chiari I malformation; foramen magnum decompression; hydrocephalus; infection

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