Fig. 1.

Midsagittal brain MR images showing the cervicomedullary junction and high cervical spine obtained in a 15-year-old girl presenting with neck pain exercise. Note the nine-year gradual progression of cerebellar tonsillar herniation from 7 mm (A) to 24 mm (D), the descent of the obex from 2 mm above the foramen magnum (A) to 8 mm below (D) and the thinning of the medulla oblongata from 8 mm (A) to 6 mm (D). A : Initial sagittal T2-weighted MR image, B : 2 years, C : 7 years, and D : 9 years after the initial presentation.