The hemispherectomy, the removal of part or all of one of the hemispheres of the brain, had also fallen almost completely out of use after its development in the 1920s, and it was reintroduced under Freeman when he returned to Hopkins. It was used when patients suffered from any of three conditions—Rasmussen's encephalitis, irregular brain development or stroke—and had failed to respond to less-drastic treatments. The technique was used and to some degree brought to public awareness by neurosurgeon Ben Carson in the 1980s. According to Carson, Freeman "helped work out many of the techniques and problems associated with the cerebral hemispherectomy."
