Findings
These images demonstrate cerebellar tonsils which extend below the level of the foramen magnum with packing. The tonsillar descent measures approximately 10 mm. There is ventricular dilatation bilaterally with relative absence of the septum pellucidum. The optic nerves appear small in size. However, the optic chiasm is normal appearance. Diffusion weighted scans show no evidence of acute infarction.The cerebral aqueduct is not well visualized on the sagittal scan. It may be obstructed. On the CSF pulsation studies there is no flow through the aqueduct. It is narrowed.
Impressions
Chiari I malformation.
Absence of the septum pellucidum with optic nerve hypoplasia raising the possibility of septo-optic dysplasia. Clinical correlation is required.Ventricular enlargement without transependymal CSF flow affecting lateral and third ventricles but sparing fourth ventricle.