Three Territory Sign

Background Multiple acute cerebral territory infarcts of undetermined origin are typically attributed to cardioembolism, most frequently atrial fibrillation. However, the importance of 3-territory involvement in association with malignancy is under-recognized. We sought to highlight the “Three Territory Sign” (TTS) (bilateral anterior and posterior circulation acute ischemic diffusion-weighted imaging [DWI] lesions), as a radiographic marker of stroke due to malignancy.

Methods We conducted a single-center retrospective analysis of patients from January 2014 to January 2016, who suffered an acute ischemic stroke with MRI-DWI at our institution, yielding 64 patients with a known malignancy and 167 patients with atrial fibrillation, excluding patients with both to eliminate bias. All DWI images were reviewed for 3-, 2-, and 1-territory lesions. Chi-square test of proportion was used to test significance between the 2 groups.

Results We found an association between the groups (malignancy vs atrial fibrillation) and the number of territory infarcts (p < 0.0001). Pairwise comparisons using the Holm p value adjustment showed no difference between 1- and 2-territory patterns (p = 0.465). However, the TTS was 6 times more likely observed within the malignancy cohort as compared to patients with atrial fibrillation (23.4% [n = 15] vs 3.5% [n = 6]) and was different from both 1-territory (p < 0.0001) and 2-territory patterns (p = 0.0032).

Conclusion The TTS is a highly specific marker and 6 times more frequently observed in malignancy-related ischemic stroke than atrial fibrillation-related ischemic stroke. Evaluation for underlying malignancy in patients with the TTS is reasonable in patients with undetermined etiology.