Figure 2B

The axial MRI slice through the foramen magnum shows much more extensive tonsillar herniation in the parasagittal plane with the appearance of crowding. It can be appreciated that a mid-sagittal section would show a generous subarachnoid space(arrow). The patient suffered from headache, dizziness and vertigo aggravated by extension of the neck. Lasting relief followed foramen magnum decompression.