A case of lateral medullary syndrome that could not be diagnosed by initial MRI

Acute vestibular syndrome (AVS) is a clinical condition characterized by dizziness or vertigo that develops acutely with nausea/vomiting, gait instability, and/or head-motion intolerance and lasts for a day or more. Most patients presenting with AVS are diagnosed as having a benign peripheral condition commonly called vestibular neuritis. However, central causes of AVS can also closely mimic benign peripheral AVS, particularly vestibular neuritis. Herein, we report a case of lateral medullary syndrome in a patient who presented with acute vertigo, in whom showing differential diagnosis from peripheral vertigo proved difficult by initial magnetic resonance imaging (MRI). A 47-year-old male patient presented to the emergency room complaining of severe vertigo and headache. The initial brain MRI showed no evidence of bleeding or stroke. Physical examination revealed left-directional horizontal nystagmus and gait disorder. There were no abnormal findings on examination of the central nervous system, other than nystagmus. However, during the clinical course, several other neurological findings became evident. A follow-up MRI performed two days after the onset of vertigo showed lateral medullary infarction, suggestive of the diagnosis of lateral medullary syndrome, and the patient was admitted to a neurological department for further treatment. Lateral medullary syndrome is caused by injury to the lateral part of the medulla in the brain. It has been reported that initial MRI of the brain sometimes fails to show abnormal findings in cases of lateral medullary syndrome. In patients presenting with acute vertigo, we should consider the possibility of central vertigo due to brainstem or cerebellar infarction, even in young patients without risk factors for cerebro-vascular disorders. Although the initial MRI findings show no signs of brain infarction in some patients of the lateral medullary syndrome presenting with AVS, physicians should keep in mind the importance to repeated neurological examinations and also a second MRI examination, if needed, to rule out the diagnosis of lateral medullary syndrome.