 There are low-lying cerebellar tonsils (left greater than right) with a pointed morphology extending up to 10 mm below the foramen magnum, to the level of posterior arch of C1. The CSF space around the brainstem and upper cervical cord by the tip of the cerebellar tonsils is effaced. There is no acute infarct, mass effect, or cerebral edema. The ventricles and basal cisterns are normal in size and configuration. There is no hydrocephalus. There is no midline shift. The skull and extracranial soft tissues are unremarkable.
Findings consistent with Chiari I malformation. No hydrocephalus.