Introduction: Steno-occlusive lesion in vertebral artery and posterior inferior cerebellar artery (PICA) or perforator occlusion could result in lateral medullary infarction. However, exact mechanism of lateral medullary infarction is not straightforward due to limited information from MR angiography (MRA) and variations of posterior circulation.
Hypothesis: The mechanism of lateral medullary infarction could be evaluated based on DWI/PWI pattern.
Methods: We selected the acute ischemic stroke patients in whom acute ischemic changes were in the lateral medulla with or without PICA territory on DWI and available PWI. We categorized cases in 4 groups based on DWI/PWI patterns. Cases with isolated lateral medullary infarction were divided into those with normal perfusion (LM) and with perfusion delay (LM-P) on PICA territory. Cases having both lateral medullary and PICA territory cerebellar infarction were further divided into those with mismatched perfusion delay (LC-UP) and with matched perfusion delay (LC-MP).
Results: A total number of 43 patients were included and DWI revealed infarction solely on lateral medulla (n=36) or both lateral medulla and cerebellum (n=7). The number of cases was 24, 12, 4 and 3 in LM, LM-P, LC-UP and LC-MP respectively. One third of isolated lateral medullary infarction shows perfusion delay in PICA territory (LM-P) suggesting proximal large artery pathology. In contrast, two thirds of isolated lateral medullary infarction may be due to perforator occlusion either by perforator pathology or less likely embolic occlusion.
Conclusion: DWI/PWI pattern classification of PICA territory is useful to understand the underlying mechanism of lateral medullary infarction.