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Spina Bifida Association of Delaware

Arnold Chiari Malformation:

Arnold Chiari Malformation (ACM) is a rare congenital anomaly in which two parts of the brain, the brainstem and the cerebellum, are longer than normal and protrude down into the spinal canal. In most cases symtoms begin in infancy, but the onset of symptoms may be delayed until adolescence. All children with Spina Bifida have ACM type II, while only 9-21% will exhibit symptoms which warrant treatment.


Symptoms include vomiting, muscle weakness in the head and face, pain at the base of the skull/upper neck, difficulty swallowing, and varying degrees of mental impairment. Paralysis of the arms and legs may also occur.


When a physician suspects ACM, an MRI (magnetic resonance imaging) will be preformed. This test is non-invasive and can detect the condition before permanent injury has occured within the nervous system. This test consists of a powerful magnet, radio waves & a computer to take pictures inside the body. It does not touch or hurt the patient and takes 30 to 90 minutes. If there is a concern about the surrounding bony spine, a CAT scan is usually used to better show the bony anatomy.


Most of these procedures report a 70% success rate in dealing with the symptoms related to ACM.

1)Decompression: removal of the overlying bone of the hindbrain malformation. 2)Drainage of the syrinx; i.e., removal of bone overlying syrinx, then opening the spinal cord to drain cavity fluid and possible catheter placement to establish a pathway for continued drainage.

As stated above, not all children with SB will exhibit symptoms, but all SB children have ACM type II.

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