[Chronic encephalitis with mesencephalic predominance. A clinico-pathologic case].

A 70 year-old woman presented with a progressive supranuclear ophthalmoplegia, with "apraxia" of eyelid opening, axial akinesia and dementia. CT scan showed a mild cortico-subcortical atrophy and there was a high level of immunoglobulins, with an oligoclonal pattern, without cell reaction in the CSF. The patient died two years after the onset. Post-mortem examination, limited to CNS, showed subacute encephalitis confined to the tectal, pretectal, subthalamic areas and to Ammon's horns. These changes and their location were strongly suggestive of polioencephalomyelitis with or without cancer, in which such a prevalent midbrain involvement has been exceptionally described.