 The left cerebellar tonsil extends 4 mm below the level of the foramen magnum, and the right 5 mm. Both maintain a normal rounded morphology.The ventricles and sulci are normal in size. There are no masses, mass effect or midline shift. The pituitary gland is normal in size. There is no evidence for intracranial hemorrhage or acute cerebral, brainstem or cerebellar infarction. No diffusion-weighted abnormalities are identified. There are no extraaxial fluid collections or subdural hematomas. Flow voids are present within the major vessels indicating patency. The paranasal sinuses and mastoid air cells are clear. There is no abnormal enhancement within the brain.
1.The left cerebellar tonsil extends 4 mm below the level of the foramen magnum, and the right 5 mm. Both maintain a normal rounded morphology. This constellation of findings is indeterminate, but the differential diagnosis is cerebellar ectopia versus Chiari malformation, with distinction requiring correlation with symptoms.2.Otherwise negative MRI of the brain including gadolinium enhancement.