Male, 5 months old, seizures. A 10 x 8 mm cystic structure is evident along the temporal horn of the right lateral ventricle approximately at the level of the choroidal fissure. The structure exerts mild mass effect upon the right hippocampal formation but no definite hippocampal signal abnormality is seen.No other discrete intracranial lesions are detected. The mesial temporal lobe structures are otherwise unremarkable. No evidence for restricted diffusion or parenchymal edema is detected. No intracranial hemorrhage or any other abnormal extra-axial collections are seen.The pituitary gland as visualized is normal for age. The brain stem and cerebellar vermis are unremarkable. The cerebellar hemispheres are fully formed and normal. The cerebellar tonsils terminate above the level of the foramen magnum. The corpus callosum is intact. The pattern of white matter myelination is appropriate for age.
A cystic structure is present along the right temporal horn with imaging features and location most suggestive of a choroidal fissure cyst. A cystic neoplasm is felt to be much less likely, though follow-up imaging with contrast should be considered to exclude this possibility.This lesion exerts mild mass-effect on the right hippocampal formation. However, the true significance of this finding relative to the patient's seizures is uncertain.