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.