mild enchroachment of cerebellar tonsils on the foramen magnum accompanied by capsulosynovial proliferative change of the atlanto-odontoid articulation. Noevidence of wedging of the cerebellar vermis, cervicomedullary kinking, syringohydromyelia, cervico-occipital assimilation, or hydrocephalus to suggest high grade chiari M
in spite of cerebellar tonsilliar ectopia, prominant retrocerebrellar CSF space is noted posteriorly above the foramen magnum.