An unexpected Holter monitor result: multiple sinus arrests in a patient with lateral medullary syndrome.

A 52-year-old man presented with vomiting, dysphagia, left-sided ataxia and dissociated sensory loss. Diffusion-weighted MRI showed evidence of acute infarct in the left lateral medulla and left medial cerebellar hemisphere, probably secondary to thromboembolism from left vertebral artery dissection. While making an uneventful recovery as an inpatient, a routine 24 h ECG was performed 2 weeks after the stroke to investigate possible paroxysmal atrial fibrillation. The recording instead revealed 56 asymptomatic episodes of sinus arrest, necessitating implantation of a permanent pacemaker to prevent sudden cardiac death. The medulla contains key structures involved in autonomic regulation, including the dorsal vagal nucleus and the nucleus tractus solitarius. Acute infarction may disrupt cardiac autonomic regulation pathways, resulting in altered parasympathetic and sympathetic outflow to the sinoatrial and atrioventricular nodes, with potentially life-threatening effects.