Low cerebellar tonsils

  • Protrusion of tonsils < 5 mm below foramen magnum
  • Tonsils are rounded inferiorly
  • Fourth ventricle is in normal position
  • Twining’s line –  horizontal line  from tuberculum sella to internal occipital protuberance. This line should traverse midway through the fourth ventricle
Read more

Elster, Allen D., and M. Y. Chen. “Chiari I malformations: clinical and radiologic reappraisal.” Radiology 183.2 (1992): 347-353.

Hofkes, Shawn K., et al. “Differentiation between symptomatic Chiari I malformation and asymptomatic tonsilar ectopia by using cerebrospinal fluid flow imaging: initial estimate of imaging accuracy.” Radiology 245.2 (2007): 532-540.