Although the effectiveness of hemispherectomy was established, the high incidence of hydrocephalus and delayed mortality from superficial cerebral hemosiderosis in up to one-third of patients led to a rapid decline in the procedure 1) 2).
In the 1970s, Rasmussen recognized that the extent of resection and the residual surgical cavity were contributing factors to superficial cerebral hemosiderosis. Preservation of the frontal and occipital lobes and disconnecting them from the rest of the brain resulted in a “functional complete but anatomical subtotal hemispherectomy,” giving rise to the functional hemispherectomy, which protected against superficial cerebral hemosiderosis and delayed hydrocephalus, and to a resurgence for the disconnection procedure 3).