Upbeat nystagmusinapatient with asmall medullary infarct

A 43 year old man presentedwith decreased sensitivity intheleft sideofthe faceand bothupper limbs,and with upbeatnystagmusand skewdeviation. MRI demonstrated a welil defined lesion compatible withan infarct intheleft side ofthemedulla, caudalandventral tothe vestibular nuclei, possibly involving the most caudalof the perihypoglossal nuclei, thenucleusintercalatus. Ocular motor studies, usingan infrared system, showedthatthenystagmusslowphase decayedexponentially, suggesting a failure ofintegration forvertical eye movements. Verticalintegration might, therefore, be performedpartlyin the nucleus intercalatus.