Anterior inferior cerebellar artery occlusion accompanied by hemorheology-documented increased blood viscosity: a case report.

Anterior inferior cerebellar artery (AICA) occlusion is a subtype of posterior circulation stroke. Confirmation of its angiomorphology and etiology is challenging because of the complex mechanisms underlying small-artery thrombogenesis. In addition to conventional factors, physicians frequently overlook hemorheological changes. In this case report, we describe right AICA occlusion in a 50-year-old man. He presented with an unsteady walk, tinnitus, dizziness, and left-sided peripheral facial palsy observed over 36 hours, accompanied by increased blood viscosity on hemorheological evaluation. Magnetic resonance imaging revealed acute infarction in the left cerebellar hemisphere and middle cerebellar peduncles. Magnetic resonance angiography (MRA) and computed tomographic angiography (CTA) failed to detect AICA occlusion, which was later confirmed using digital subtraction angiography. Repeat routine blood examinations showed elevated erythrocyte and leukocyte counts and serum hemoglobin concentrations that persisted over many days. Hemorheological evaluation revealed increased whole blood viscosity at a low shear rate. AICA occlusion should thus be diagnosed based on its initial characteristic manifestations; notably, MRA and CTA may fail to detect arterial occlusion. The importance of hemorheological change as a factor of stroke is frequently neglected. We therefore report this case hoping to emphasize its relevance, especially in small-artery occlusion.