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Low lying cerebellar tonsils which extend below the margins of the foramen magnum to the level of C2/3. There is no evidence of a syrinx or hydrocephalus. Features are consistent with a Chiari 1 malformation.
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The patient went on to have a posterior fossa decompression with resection of the occipital bone and posterior arch of C1 with a duroplasty. A pseudomeningocele has developed.