Posterior inferior cerebellar artery (PICA) dissecting aneurysm and subarachnoid hemorrhage

Case contributed by Prof Peter Mitchell


Headache of abrupt onset. Deterioration in conscious state, WFNS grade 4, intubated and ventilated.

Patient Data

Age: 50
Gender: Female

Extensive subarachnoid blood is demonstrated within the suprasellar, ambient, and quadrigeminal plate cisterns and the sylvian fissures bilaterally. Large volume of blood also fills prepontine cistern and extends through foramen magnum. Intraventricular blood demonstrated within the lateral, third and fourth ventricles. Periventricular hypodensity likely related to chronic microvascular ischemia.

A complex, multiple aneurysm arises from the right posterior inferior cerebellar artery (PICA) approximately 12mm beyond its origin, with both fusiform and saccular components.  A high grade stenosis in the more proximal PICA supports a diagnosis of dissecting aneurysm.

Conclusion: Large volume subarachnoid hemorrhage (largest volume posterior fossa) with
intraventricular blood and hydrocephalus, with a large right PICA aneurysm.

A complex abnormality of the right PICA is shown - shortly after its origin there is an eccentric high-grade stenosis with small false aneurysm, and some 10 mm beyond this is a smaller 3 mm mixed fusiform and saccular aneurysm, just beyond this a larger 4.5 millimeter aneurysm at the bifurcation of PICA, incorporating both branches in its base. The left vertebral is patent and fills the basilar but is of smaller caliber. No other intracranial aneurysm, and no arteriovenous or dural arteriovenous fistula or malformation is shown.

Dissecting aneurysm of the right posterior inferior cerebellar artery, with dissection commencing just beyond the origin of the vessel, with 2 larger aneurysms arising from the body of PICA beyond this, managed with PICA occlusion. Balloon supported coil embolization occlusion of the PICA, high grade stenosis precluding trapping the aneurysms with coils distally. No retrograde opacification of PICA from ipsilateral AICA.

Day 2 no evidence of PICA territory infarction. 

Case Discussion

PICA dissection without involvement of the vertebral artery is rare but reported, and usually requires management with sacrifice of the vessel.  Endovascular sacrifice is preferred over microsurgical exploration.  In appropriate clinical circumstances, balloon occlusion testing of adequacy of collaterals can be considered.

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Case information

rID: 22956
Published: 8th May 2013
Last edited: 14th Aug 2019
Inclusion in quiz mode: Included