Artery of percheron infarction: imaging patterns and clinical spectrum

Abstract

Background and purpose: Occlusion of the AOP results in a characteristic pattern of ischemia: bilateral paramedian thalamus with or without midbrain involvement. Although the classic imaging findings are often recognized, only a few small case series and isolated cases of AOP infarction have been reported. The purpose of this study was to characterize the complete imaging spectrum of AOP infarction on the basis of a large series of cases obtained from multiple institutions.

Materials and methods: Imaging and clinical data of 37 patients with AOP infarction from 2000 to 2009 were reviewed retrospectively. The primary imaging criterion for inclusion was an abnormal signal intensity on MR imaging and/or hypoattenuation on CT involving distinct arterial zones of the bilateral paramedian thalami with or without rostral midbrain involvement. Patients were excluded if there was a neoplastic, infectious, or inflammatory etiology.

Results: We identified 4 ischemic patterns of AOP infarction: 1) bilateral paramedian thalamic with midbrain (43%), 2) bilateral paramedian thalamic without midbrain (38%), 3) bilateral paramedian thalamic with anterior thalamus and midbrain (14%), and 4) bilateral paramedian thalamic with anterior thalamus without midbrain (5%). A previously unreported finding (the "V" sign) on FLAIR and DWI sequences was identified in 67% of cases of AOP infarction with midbrain involvement and supports the diagnosis when present.

Conclusions: The 4 distinct patterns of ischemia identified in our large case series, along with the midbrain V sign, should improve recognition of AOP infarction and assist with the neurologic evaluation and management of patients with thalamic strokes.

Fig 1.

A, Conventional anatomy demonstrating paired thalamic and midbrain perforating arteries. B, AOP arising as a single unpaired trunk from P1 supplying the bilateral paramedian thalami and rostral midbrain. Reprinted with permission from Amirsys Inc.

Fig 2.

Collective extent of all 4 infarct patterns at the level of the thalamus (A) and midbrain (B) from all 37 cases superimposed.

Fig 3.

Case 2 (A and B) and case 16 (C and D). Axial FLAIR MR images at the level the thalamus (A and C) and midbrain (B and D) demonstrate bilateral paramedian thalamic and midbrain involvement (pattern 1). Notice the hyperintense signal intensity along the pial surface of the midbrain interpeduncular fossa representing the V sign (B and D).

Fig 4.

Case 22. Axial FLAIR (A and B) and DWI (C and D) images at the level of the thalamus (A and C) and midbrain (B and D) demonstrate infarction of the bilateral paramedian thalami without midbrain involvement (pattern 2).

Fig 5.

Axial FLAIR MR images through the midbrain from cases 31 (A), 5 (B), and 9 (C) show a V-shaped hyperintense signal intensity along the pial surface of the midbrain at the interpeduncular fossa (the V sign).

Fig 6.

DSA of the left vertebral injection, lateral (A) and anteroposterior (B) views, and a coronal CTA image (C) from case 23 demonstrate a large unpaired thalamic perforating artery (arrows) arising from the proximal P1 segment supplying the bilateral thalami (ie, an AOP).