A further problem in determining a strategy for managing patients with a Chiari I malformation is that the criteria for surgical intervention are nebulous. Some patients are symptomatic with only a minor degree of tonsillar ectopia and others with severe displacement of the cerebellar tonsils into the upper spinal canal have no symptoms. Since the correction of a Chiari I malformation requires surgery it is generally reserved for patients showing clear evidence of progressive clinical symptoms. Any technique that can provide information on pathological changes within the spinal cord would be a very important complement to the clinical data and the anatomical information provided by conventional MRI. At present it is difficult to predict which patients are predisposed to developing syringomyelia on the basis of conventional imaging findings alone and DW-MRI may be able to provide useful complementary information.