A 28-year-old woman presented with acute right hemiparesis evolving to bilateral hemiplegia and a mute state within 1 week on a background of paranoid psychosis of 8 years duration. CT scan revealed multiple bilateral hypodense enhancing lesions in the central white matter. Biopsy of the lesion showed lamellar alternating zones of demyelination and remyelination, typical of Balo's concentric sclerosis, an acute variant of multiple sclerosis. Immunohistochemical staining for neurofilament showed greater damage to the axis cylinders by the disease than generally perceived by silver stains. Steroid therapy produced a gratifying and sustained improvement. Follow up CT scans and psychometry revealed regression of the demyelinating lesions and improvement of the cognitive state.