AN MRI ANALYSIS OF BRAIN-STEM AND CEREBELLAR LESIONS AND OLIVARY HYPERTROPHY

We describe the relations between primary brain stem or cerebellar inf arct or haemorrhage and secondary inferior olivary pseudohypertrophy ( OPH). We identified 17 patients (43.6 %) among 39 with brain stem or c erebellar vascular disease who had MRI follow-up more than 3 months af ter their ictus, with OPH. The primary lesions in the 22 cases without OPH were 11 haemorrhages, including 8 medial cerebellar and 3 brain s tem lesions, and 11 infarcts: 4 brain stem lesions without accompanyin g cerebellar involvement, 2 cerebellar infarcts with brain stem extens ion, and 5 cerebellar lesions without a brain stem infarct. The causat ive lesion in the 17 patients with OPH included 5 brain stem and 7 cer ebellar haemorrhages and 5 brain stem infarcts; no cerebellar infarcts without brain stem involvement were found to cause OPH. Primary invol vement of the tegmentum of the brain stem was closely related to secon dary OPH, but we could not characterise MRI differences in the cerebel lar lesions between the patients with or without OPH.