Evaluate for cause of headache with neck extension; rule out mass such as colloid cyst. There is a small posterior fossa and low lying cerebellar tonsils that extend up to 9 mm inferior to the foramen magnum with associated effacement of the regional cerebrospinal fluid. There is no evidence of intracranial hemorrhage, mass, or acute infarct. The brain parenchymal signal and pituitary gland appear unremarkable. The ventricles and basal cisterns are normal in size and configuration. There is no midline shift. The major cerebral flow voids are intact. The paranasal sinuses are grossly unremarkable. There appear to be punctate left lacrimal gland cysts, although these are incompletely characterized.
1. Low-lying cerebellar tonsils and small posterior fossa are suggestive of Chiari I malformation.2. No evidence of colloid cyst or other intracranial mass lesions.