RESUMEN
Lateral medullary syndrome (LMS), also known as Wallenberg's syndrome, PICA syndrome, results from occlusion of the posterior inferior cerebellar artery, with associated infarction of parts of medulla oblongata, and cerebellum on the ipsilateral side. It often manifests as various patterns of sensory, motor, and autonomic deficits. While sensorimotor dysfunction presents as a predicted pattern of clinical signs and symptoms, autonomic dysfunction is usually less clinically apparent, and can be easily mistaken as a concomitant pathology in the end organ it affects. In this case, we present a case of an unusual pattern of cardiac arrhythmia as the first objective finding of LMS, caused by autonomic instability following infarction of vagus nerve nuclei in the medulla.