The frequency of intracranial and intraspinal neoplasms in the resident population of Rochester, Minnesota.

T HE purpose of this paper is to report the incidence, prevalence, and death ratio for various neoplasms affecting the central nervous system in the resident population of Rochester, Minnesota, for the 10-year period 1945 to 1954, inclusive. It is desirable to have such statistics for various populations. Such information might disclose differences in frequency by race, geographic area or characteristics of population and would be of value in planning for research and needs of medical care. Epidemiologic studies in areas with appreciable variances in incidence might provide relevant clues to etiology. Most previous reports dealing with the frequency of neoplasms affecting the central nervous system have been based on the personal experience of practising neurosurgeons or upon selected necropsy series or proportionate rates of hospital admissions. These data, although of value in describing clinical or pathologic experiences, do not necessarily provide a true picture of the incidence of neoplasms or of their frequency by type in the total population. Surgical series are more likely to be representative of operable neoplasms rather than of all neoplasms in the population; operability, in turn, is influenced by such characteristics as age and general health of the patient and by the presumed type or accessibility of the lesion. The interest and reputation of the surgeon may influence the nature of his series; the relatively high proportion of pituitary tumors in Cushing's series l of intracranial neoplasms is an often cited example of this type of bias. The admission policy of a hospital, such as age, sex or racial limitations, or its emphasis on neurosurgical problems may present another form of bias that prevents accurate generalizations from its data. Series of cases seen at necropsy may likewise be unrepresentative because of the frequency of special interests in research in neoplastic conditions and because of the greater effort expended by the resident staff in obtaining permission for necropsy in cases of puzzling or relatively uncom-