There is a well-marginated defect with a thin sclerotic border in the midline of the occipital bone measuring 8.5 x 3.3 mm. Superficial to the defect, a well-defined ovoid heterogeneous lesion with areas of fluid attenuation is seen in the scalp measuring 1.8 x 0.8 x 1.9 cm, which appears to communicate with the intracranial space.
Enlarged retrocerebellar CSF space with an intact cerebellar vermis. No communication with the fourth ventricle is seen. Findings are compatible with a mega cisternal magna.