Baló's encephalitis periaxialis concentrica.

In 1928, Baló described a law student with an unusual fatal illness marked by aphasia and a right hemiplegia, with later optic neuritis and normal cerebrospinal fluid. At autopsy, he found a disease of the white matter characterised by foci varying in size from a lentil to that of a pigeon's egg and presenting gray softening and, in part, concentricity, where the medullary sheaths were destroyed and the axis cylinders were intact. He was uncertain whether this was a variant of acute multiple sclerosis or of Schilder's disease. The basis of concentric sclerosis is still unclear though current opinion favours a variant of acute multiple sclerosis.