There has been much speculation as to the extent of cerebral involvement in poliomyelitis. Recent pathologic and experimental material has suggested that it is greater than what would be suspected on clinical grounds.
The proportion of cases with frank clinical manifestations of encephalitis is relatively small in most epidemics of poliomyelitis. In those instances, the drowsiness deepening into coma, often profound and prolonged, the tremors and the rigidity, leave no doubt as to the invasion of the brain by the disease process. Involvement of the brain is much less certain in milder clinical pictures, although it has been suspected as an explanation of the unusual-emotional states often encountered during the acute stage of poliomyelitis. As for the disturbed behavior which has been known to occur as a late sequel of poliomyelitis, and which is being extensively studied,1 most explanations have been based on the psychologic trauma of crippling disabilities