AICA fusiform

This is a case of AICA dissecting aneurysm with distal territory reconstitution by the Primitive Lateral Basivertebral Anastomosis of Padget (PLBVA).

The  MRI showed a fusiform aneurysm which enlarged over several years time. The patient presented with transient hearing loss. All of the above show typical features of a dissecting fusiform aneurysm, including significant stenosis distal to the aneurysm. There is a hypoplastic left PICA, and duplicated AICAs — with the larger inferior one having the aneurysm and supplying the inferior hemispheric cerebellar territory, as dominant AICA-PICA does. VR images, as well as DSA images above, beautifully show the PLBVA just lateral to the aneurysm, connecting the more superior smaller AICA with the lower AICA segments.  Injection of basilar above the larger inferior AICA and below the superior AICA show the PLBVA network.  Why does this network develop? — a collateral response to flow constraint in the AICA branch distal to the aneurysm.  In other words, post-aneurysmal stenosis promoted the growth of this normally tiny PLBVA collateral. 

To prove the efficiency of the PLBVA we performed occlusion test with subselective catheterization with tip of Headway Duo (yellow arrow) in the stenotic segment just distal to the aneurysm (proximal marker = blue arrow). Injecting from the guide with Headway Duo in above position as an effective test occlusion shows full reconstitution of distal AICA inferior cerebellar territory via the PLBVA.  

At this point occlusion of the aneurysm with sacrifice was performed safely.

The Primitive Lateral Basivertebral Anastomosis of Padget (PLBVA) is an important longitudinal anastomotic network that runs along the brainstem / anterior cerebellar surface, in parallel with the basilar artery.  It is believed to be a homolog of the lateral spinal artery, in the same way, that the basilar is a homolog of the anterior spinal artery.  Very rarely seen. aneurysm with sacrifice was performed safely.