INFARCTION OF THE LOWER BRAIN-STEM - CLINICAL, ETIOLOGIC AND MRI-TOPOGRAPHICAL CORRELATIONS

Using a standard protocol including MRI and magnetic resonance angiogr aphy (MRA), we studied 28 consecutive patients, all with an acute infa rct in the lower brainstem. MRI patterns above and below the inferior olivary nucleus enabled identification of six topographical types of i nfarct. small midlateral, dorsolateral, inferolateral, large inferodor solateral, dorsal and paramedian infarcts. Small midlateral, dorsolate ral, inferolateral and inferodorsolateral infarcts were the most commo n types and were associated with Wallenberg's syndrome, with specific clusters and severity of neurological features in each of the four gro ups. Dorsal infarcts were both anatomically and clinically overshadowe d by a constant associated cerebellar infarct in the posterior inferio r cerebellar artery (PICA) territory. Paramedian infarction led to cro ssed tongue and sensorimotor hemiplegia, while a patient with an almos t complete hemimedullary infarct had unusual ipsilateral sensory and m otor disturbances due to lesion extension toward the upper spinal cord . A coexisting cerebellar infarct was present in 36% of the cases, but was never found with midlateral or inferolateral infarct. Angiography showed an embolic occlusion of the PICA in Jive patients (18%), four of them having dorsal or dorsolateral infarct. Atheromatosis was by fa r the most frequent stroke aetiology (72%), with intracranial vertebra l artery tight stenosis or occlusion in 28% of the cases and in 75% of the cases with large inferodorsolateral infarct. Vertebral artery dis section and cardioembolism accounted each for 14% of the cases, the la tter being associated with dorsal infarct. Our study shows that differ ences in topographical patterns of infarction in the lower brainstem p robably reflect differences in aetiopathogenic mechanisms.