58 year-old who became acutely unresponsive while talking on the phone




CT noncontrast




       
CTA axial source images




CTA coronal and 3D recons




Right vertebral artery injection lateral, AP, and 3D recons




Right Vertebral artery injection AP and lateral views s/p coiling


Findings:

CT: diffuse subarachnoid hemorrhage
CTA and angiogram:  Right vertebral artery focal enlargement just distal to the PICA origin involving the anterior spinal artery origin

DDX:

Fusiform aneurysm, dissecting aneurysm, FMD


Diagnosis:

Right vertebral artery dissecting aneurysm just distal to the PICA origin involving the anterior spinal artery


Discussion:

A vertebral artery dissection usually begins with an expanding hematoma in the vessel wall.  This intramural hematoma can arise spontaneously or secondary to minor trauma.  It also can be introduced through an intimal flap that develops at the level of the inner lumen of the vessel.  Subadventitial dissections tend to cause pseudoaneurysmal dilation of the vertebral artery, which may compress adjacent neurologic structures. These subadventitial dissections are prone to rupture through the adventitia, resulting in subarachnoid hemorrhage. In an autopsy series of more than 100 patients with subarachnoid hemorrhage, 5% of the hemorrhages were from vertebral dissection.  Due to their natural history to rebleed, rapid treatment, often with coil embolization is favored.  In this case, a risk factor was the presence of the anterior spinal artery origin within the dissection.  Fortunately, after coiling there was retrograde  filling  of  the  anterior  spinal  artery  via  muscular perforators  from  the  proximal  right  vertebral  artery.

Submitted by Dinesh Rao, MD, UW Neuroradiology Fellow

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