Fourth ventricle posterior inferior cerebellar artery aneurysm

Case contributed by Dr Bruno Di Muzio


Incidental finding on brain CT for other reasons.

Patient Data

Age: 45
Gender: Female

There is a 4 mm x 4 mm enhancing nodule in the posterior fossa, likely to arise from the anterior vermis and possibly in continuity with the inferior fourth ventricle. Very small vessels are noted to feed into this nodule.

No acute hemorrhage or infarction identified.

Normal grey white matter differentiation. The ventricles and basal cisterns are unremarkable for patient's age.

The visualized paranasal sinuses and mastoid air cells are clear.

Conclusion: There is a small enhancing nodule within the posterior fossa is of uncertain significance and unlikely to be contributing to the patient's symptoms. It is unclear whether this arises from the 4th ventricle or whether it is in continuity with choroid plexus. MRI recommended to further characterization.

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.


Small arterial aneurysm within the fourth ventricle. 

The left vertebral artery has a mildly tortuous origin, of reasonable caliber. A C1 origin of the left PICA with a large inferior loop projecting into the upper cervical spine passes superiorly through the foramen magnum, and almost in the midline, with a broad necked, 5 mm x 5 mm left PICA aneurysm.

Case Discussion

This case illustrates an incidental finding characterized by a small sacular aneurysm arising from an arterial branch within the fourth ventricle. DSA study confirms to be a posterior inferior cerebellar artery aneurysm.

With regards to possible endovascular treatment options, these would include aneurysm occlusion and parent artery sacrifice (not favored given the very large territory supplied); stent-assisted coil embolization; and a stent without coils (flow diverting or otherwise). Other than the first of these options, all would require dual antiplatelet therapy, complicated by the current need for full anticoagulation (ceased and converted to clexane prior to this procedure). All options carry a moderate risk of PICA territory infarction.

Surgery to clip the aneurysm was proposed and performed without major complications. 

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Case information

rID: 39596
Published: 11th Sep 2015
Last edited: 9th Jul 2016
Tag: rmh
Inclusion in quiz mode: Included

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