The previously identified nodular lesion within the fourth ventricle is again demonstrated and corresponds to a vascular aneurysm, unfortunately it is not possible to identify the origin of this arterial branch in this imaging protocol (probably arising from the posterior inferior cerebellar artery).
The lesion measures 4.4 x 3.5 mm in its maximum axial diameters.
There are no abnormal focal areas of altered signal intensity in the cerebral hemispheres, brainstem or cerebellum. Ventricular system and cisternal spaces appear normal. No evidence of intracranial space occupying lesion. There is no shift of the midline structures. The visualized orbits, paranasal sinuses and calvarium appear unremarkable.
Conclusion:
Small arterial aneurysm within the fourth ventricle.