Extracranial vertebral artery involvement in neurofibromatosis type I. Report of four cases and literature review

Abstract

Neurofibromatosis type 1 (NF-1) is one of the most common inherited diseases and as an autosomal dominant genetic disorder results from NF-1 gene mutation with 100% penetration and wide phenotypic variability. The disease can involve a wide variety of tissues derived from all three embryonic layers. NF-1 vasculopathy has been described primarily in peripheral arteries, but arteries supplying the CNS may also be involved. Of those, extracranial vertebral involvement is the commonest and most important. A series of four patients with NF-1 and vascular disease of the vertebral artery is described with a review of the pathophysiology, vascular phenotypes, their management and the pertinent literature.

Figure 1

Case 1. A) Sagittal T2-W MRI (A) revealing large flow void epidural structures at C2-5, compatible with venous pouches and a partially thrombosed superior portion, causing severe cord compression. B) Axial T1-W MRI post Gd enhancement showing extension of the epidural venous pouches along the left neural foramen with nerve root compressions. C,D) Right and left vertebral angiograms demonstrating AV shunting from the LVA at C4 level, compatible with VVAVF. Dysplastic change and tortuousity of the LVA proximal and distal to the fistula are also noted with indirect collaterals from the left ascending cervical artery and thyrocervical trunk due to a "sump effect".

Figure 2

Case 1 (continued),A,B) Left cervical arteries angiogram: collateral contribution to the fistula throughout deep cervical and thyrocervical trunk. C,D) The control after glue and particle embolization. E,F) The right vertebral angiographic control after completed left vertebral occlusion with no remaining fistula.

Figure 3

Case 2. Right vertebral angiogram AP view pre and post gold valve balloon (GVB) embolization demonstrating dysplastic change of the RVA with early filling of the epidural venous plexus at C4 level which completely disappeared after deployment of one No. 9 GVB that enabled preservation of the RVA.

Figure 4

Case 3. Right vertebral angiogram, AP view, pre-embolization (A) and left vertebral angiogram (B) lateral view pre-embolization both demonstrate an AV shunt at the left C3-4 level, with venous blood draining into dilated epidural pouches and then further draining into the jugular veins. There is complete obliteration of the VVAVF after GDC embolization and sacrifice of the LVA (C, right VA angiogram, AP view).

Figure 5

Case 4. On T2W MRI sequences enlargement of transverse foramen due to a mass presumably representing a large aneurysm (high signal due to low flow and turbulence) can be seen that demonstrates contrast enhancement (A-C: T1 weighted images after contrast) and bone erosion on CT (D). Adjacent structures are compressed.

Figure 6

Case 4 . Angiography (A: right vertebral artery injection, B: left vertebral artery injection) reveals a large fusiform shaped aneurysm at C5-6 level of the RVA with good supply to the posterior circulation through the LVA. After GDC embolization contrast stagnation in the aneurysm was noted immediately after sacrifice of the proximal RVA. Post embolization angiograms (D,E) confirmed complete obliteration of the aneurysm.

Figure 7

Schematic Illustration of the pathophysiology of the presented cases. In the first three patients, a vertebrovertebral arteriovenous fistula was present. In these drawings, the dysplastic artery ruptured to a venous vertebral compartment and major important reflux to the epidural venous plexus causing spinal cord and radicular compression can be appreciated (AC). D) Illustration of the vertebral aneurysm with irregular and thick walls of the RVA associated with adjacent bone erosion from the pulsatility and enlargement of the transverse foramen causing compression of the exiting nerve root as was present in patient 4.