Imaging features of vertebral artery fenestration

Abstract

Purpose: Vertebral artery fenestration (VAF) is a rare congenital vascular anomaly which has been associated with intracranial aneurysm. VAF can share some similar imaging features with vertebral artery dissection (VAD), which may confound diagnosis of the latter on CT and MR angiography. The purpose of this investigation is to assess the prevalence of VAF, evaluate its association with other vascular anomalies, and identify imaging features to help in distinguishing VAF and VAD.

Methods: Using keyword search on CTA and MRA head and neck imaging reports from 2010 to 2017, cases of VAF and VAD were retrospectively identified and imaging was reviewed. Imaging features including laterality; vertebral segment; length of affected segment; presence, number, and caliber of lumen(s); and presence of other vascular abnormalities were recorded for all cases and subsequently compared using Pearson's chi-squared test to assess for significant differences between the groups. Patient age, gender, and clinical presentations were also recorded.

Results: Of 64,888 CT and MR angiographic examinations performed, VAF was identified in 67 (0.1%) and VAD in 54 (0.1%) patients. Compared with VADs, VAFs were shorter in length (p < 0.001), wider in luminal diameter (p < 0.001), more likely to occur at the V4 segment (p < 0.01), more likely to have two distinct lumens rather than one (p < 0.01), and less likely to present post-trauma (p < 0.01). Coexisting intracranial aneurysms were identified in 9% of patients with VAF.

Conclusion: VAFs, although rare, can be readily distinguished from VADs on angiographic imaging. Diagnosis of VAF should prompt review for intracranial aneurysm.

Keywords: Angiography; Dissection; Fenestration.

Fig. 1

Traumatic VA dissection. a Axial CTA image of 67-year-old female presenting with C2 fracture-dislocation with right vertebral artery dissection (arrow). Note diminished caliber of the right vertebral artery compared with left. b 3D reconstruction shows diminutive and slightly irregular caliber of the right vertebral artery (arrow) compared with normal caliber left vertebral artery (arrowhead)

Fig. 2

VA fenestration. a Axial CTA image from 75-year-old male presenting with left leg and hand weakness. Focal fenestration within the left vertebral artery (arrow) is noted. Note appearance of two lumens of unequal size. b 3D reconstruction of shows focal duplication of lumens within the left vertebral artery (single arrowhead) creating a “needle eye” or fenestrated appearance (arrow). Left internal carotid artery indicated by double arrowheads

Fig. 3

VA dissection. Axial (b) and MIP reconstruction (b) from 3D time of flight MRA neck in a 49-year-old male presenting with acute onset of vertigo and lower extremity weakness show very minimal flow related signal within the right vertebral artery (white arrows), indicating dissection. Note that the entire vertebral artery segment is involved, a single lumen in present, and diminished caliber of the affected vessel is evident

Fig. 4

Initial diagnosis of dissection recategorized as fenestration. Axial (a) image from CTA neck in a 36-year-old female with history of “follow-up dissection” shows two separate lumens of unequal caliber in the left vertebral artery foramen (arrow). Coronal reformatted (b, arrow) and 3D reconstructed (c, arrowhead) images in same patient demonstrates short segment vessel duplication in “needle eye” configuration, more compelling for fenestration rather than dissection. The imaging appearance remained stable on follow-up CTA performed 3 years later