Ischemic and hemorrhagic brain stem lesions mimicking diabetic ophthalmoplegia.

Two patients with diabetes mellitus, one of them with an isolated third cranial nerve palsy and the other with an isolated sixth cranial nerve palsy, are presented. MRI investigations including diffusion-weighted MRI revealed a small ischemic brain stem lesion in the former and a small hemorrhagic brain stem lesion in the latter. In the former case wallerian degeneration of the nerve fascicle within the mesencephalon was also detected. These cases indicate that vascular accidents of the brain stem may masquerade as fascicular or infranuclear disturbance of the oculomotor or abducens nerve; therefore, it is important to include brain stem lesions into the differential diagnosis of isolated ophthalmoplegia. Thorough investigation by MRI including diffusion-weighted MRI is helpful for correct diagnosis.