Isolated Ocular Ipsipulsion as a Clue to Central Vertigo in Lateral Medullary Infarction

<b>Background:</b> Horizontal conjugate eye deviation (HCED) is typically associated with supratentorial strokes affecting the frontal eye fields and associated pathways. However, a rare form of HCED, ocular ipsipulsion, is caused by a lateral medullary lesion. The presumed mechanism involves disruption of decussating olivocerebellar fibers, leading to an imbalance in vestibular nuclei activity. <b>Purpose:</b> To report a case of isolated ocular ipsipulsion as a diagnostic clue to central vertigo. <b>Research Design:</b> Case report. <b>Study Sample:</b> An 82-year-old man with a right lateral medullary infarction. <b>Data Collection:</b> Neurological examination and brain magnetic resonance imaging (MRI) were performed. Ocular findings were documented through bedside observation and video recording. <b>Results:</b> The patient presented with acute vertigo and HCED consistent with ocular ipsipulsion, without other neurological signs. On brain MRI a right lateral medullary infarction was observed. <b>Conclusions:</b> This oculomotor dysfunction can be the only clue in the neurological examination to suspect a central vertigo. Clinicians should be aware of this sign and include its assessment in the bedside evaluation of acute vertigo in the emergency setting if a central cause is suspected.