[Magnetic resonance imaging in horizontal oculomotor paralysis caused by infarction].

Four patients with focal brainstem ischemic strokes and various types of horizontal oculomotor disturbances have been studied clinically and radiologically. One had a six nerve palsy, one a unilateral internuclear ophthalmoplegia, one a Fisher's one-and-a-half syndrome, and one a paramedian pontine reticular formation syndrome with a sixth nerve palsy. In all patients a C.T. Scan and a Magnetic Resonance Imaging (MRI) were obtained. The MRI study was performed on a CGR Magniscan 5000 with a superconducting magnet of 0.5 Tesla. In all patients a hypersignal in T2 weighted images was shown and corresponded to the brainstem infarct. MRI allowed accurate delineation of the lesion and clinico-radiologic correlations in three patients. But the low specificity of MRI does not permit to distinguish edema from necrosis, gliosis or demyelination in a region with a pathological MRI signal. In one patient this low specificity and perhaps partial volume effects decreased the accuracy of the clinico-topographic correlation.