Clinical Practice and Cases in Emergency Medicine

Introduction: A posterior circulation stroke at the level of the basilar artery can cause ischemia to the brainstem, cerebellum, and occipital lobes.
Posterior circulation strokes are notoriously more difficult to clinically diagnose than anterior circulation strokes, with a variety of presenting symptoms including altered mental status, dizziness, vision changes, nausea, and vomiting. Anisocoria has been reported to occur in rare cases.

Case Report: We present two cases where patients had an acute episode of altered mental status with a key exam finding of anisocoria, or unequal pupil sizes. The combination of anisocoria
and acute mental status decline are classically associated with traumatic brain injury, increased intracranial pressure, or both. In each of the two cases presented, acute basilar artery occlusion was seen on computed tomography with angiography.

Conclusion: When presented with acute decline in mental status and anisocoria, early clinicalsuspicion of an acute basilar artery occlusion is crucial in diagnosing and managing these patients
with debilitating acute posterior stroke. Time-sensitive interventions such as thrombolytics and mechanical thrombectomy can be lifesaving.