 There is persistent inferior herniation with rounded contour of the cerebellar tonsils. Given the limitations of technique and measurement error, the herniation measures up to 4 mm below the foramen magnum when measured at the same position as on the prior exam and is unchanged. There is no acute infarct, mass effect, or cerebral edema. There is no hydrocephalus. The ventricles are unchanged, normal in size and configuration. There is no midline shift. The skull and extracranial soft tissues are unremarkable.
Mild inferior cerebellar tonsillar herniation without significant change. No hydrocephalus or change in ventricular caliber.