Headaches. Chiari malformation. Low levels of thyrotropin. BRAIN:The cerebellar tonsils are peg-shaped and extend to 11 mm below the level of foramen magnum, resulting in crowding at this level with near complete obliteration of the CSF space at the level of the cervicomedullary junction. Of note, the odontoid process is mildly retroflexed.There is no dilatation of the ventricles. There is no evidence of intracranial hemorrhage, mass, or acute infarct. There is a developmental venous anomaly in the left frontal lobe, which is a common incidental finding. Otherwise, the brain parenchyma is unremarkable and there is no abnormal intracranial enhancement. There is no midline shift. The major cerebral flow voids are intact. There is trace mucosal thickening in the maxillary and anterior ethmoid sinuses.CSF flow study shows preserved anterior but no posterior CSF flow at the level of foramen magnum. Immediately below the level of foramen magnum, there is preserved anterior and posterior CSF flow.PITUITARY:The pituitary gland is normal in size. It shows homogenous contrast enhancement without definite focal lesion. Pituitary infundibulum is normal thickness and midline. The optic chiasm and hypothalamus are unremarkable. The cavernous sinuses are symmetric and unremarkable as well.
1.Chiari I malformation with attenuated CSF flow dorsally at the level of foramen magnum as described above, but no ventricular dilatation. The odontoid process is mild retroflexed.2.Left frontal developmental venous anomaly, which is a common incidental finding. The brain is otherwise unremarkable.3.Normal pituitary MRI without definite focal lesion.