Acute Distal Vertebral Artery Occlusion in Patients with Asymmetrical Vertebral Artery Geometry: Role of Black-Blood-Enhanced MR Imaging

Abstract

Background: The purpose of this study was to evaluate the diagnostic value of contrast enhancement in a unilateral distal vertebral artery (VA) using black blood (BB)-enhanced magnetic resonance (MR) imaging in patients with acute neurological symptoms and asymmetrical VA geometry. Methods: From January 2020 to August 2021, we retrospectively analyzed BB-contrast-enhanced MR imaging and MR angiography (MRA) findings in stroke patients visiting the emergency room for an evaluation of acute neurological symptoms. We classified four patterns according to asymmetrical VA geometry using MRA and contrast enhancement using BB-enhanced MR imaging: type 1 = enhanced VA + no visualization of VA, type 2 = enhanced VA + hypoplastic VA, type 3 = non-enhanced VA + hypoplastic VA, or type 4 = non-enhanced VA + no visualization of VA. Results: In total, 288 patients (type 1 = 65, type 2 = 17, type 3 = 130, type 4 = 76) were enrolled in this study. Of these patients, 82 (28.5%) showed contrast enhancement of a unilateral distal VA on BB-enhanced MR imaging, and 51 (17.8%) had positive findings on diffusion-weighted imaging (DWI) in the ipsilateral medulla, pons, or posterior inferior cerebellar artery (PICA) territory. The contrast enhancement of a unilateral distal VA using BB-enhanced MR imaging demonstrated a significantly higher prevalence in patients with acute infarction on DWI (50.0% vs. 4.9%, p < 0.001). Conclusions: The contrast enhancement of a unilateral distal VA on BB-enhanced MR imaging is associated with acute infarction of the medulla, pons, or PICA territory and suggests acute occlusion of a distal VA.

Keywords: black blood imaging; contrast enhancement; magnetic resonance imaging; stroke.

Figure 1

Four types of asymmetrical VA geometry on black blood enhanced MR and MRA. (A) Type 1 = unilateral contrast-enhanced VA + no visualization of VA on MRA; (B) Type 2 = unilateral enhanced VA + hypoplastic VA; (C) Type 3 = no enhanced VA + hypoplastic VA; (D) Type 4 = unilateral complete occlusion of VA + no visualization of VA.

Figure 2

An 83-year-old woman with acute vertigo attack. (A) Diffusion-weighted imaging shows the acute infarction in the left posterior inferior cerebellar artery territory (arrows); (B) Contrast-enhanced MRA shows no visualization of the left vertebral artery; (C) Axial imaging of black-blood enhanced MR imaging shows strong enhancement of left vertebral artery (arrow); (D) Coronal reformatted imaging of black-blood-enhanced MR imaging shows long segment contrast enhancement of left vertebral artery (arrows). This finding suggests contrast stagnation by acute occlusion of the distal vertebral artery related to acute infarction of the posterior inferior cerebellar artery territory.