In a hospital-based study of almost 174,000 total births during 1968–1976, the authors found the incidence of congenital hydrocephalus to be 66 cases per 100,000 births. There was a significantly higher frequency in children born to mothers who themselves had been born in Puerto Rico but no significant difference in incidence between whites and blacks. The influences of maternal age, previous pregnancies, socioeconomic status, temporal and other factors are assessed and compared to previous reports.

A method of measuring flow rate through cerebrospinal fluid (CSF) shunts is reported. It consists of two thermistors in series applied to the skin over the shunt tubing. The thermistors respond by a drop in measured temperature following application of an ice cube placed on the skin overlying the proximal shunt tube. The time required for the thermal response to travel between the two thermistors is related to the velocity of flow through the shunt tubing. Flow rate can then be calculated using the internal diameter of the tubing. A series of animal experiments employing a constant infusion of mock CSF through subcutaneously implanted shunt tubing showed excellent correlation between calculated flow rates and actual infusion rates. The device is noninvasive and easily adapted to use in patients. The measurements are readily repeatable.