Continuous and intermittent measurement of intracranial pressure by Ladd monitor.

Controversy exists as to whether the force of application of the sensor of the Ladd monitor to the anterior fontanelle affects the accuracy of measurements of intracranial pressure. To resolve this problem, an artificial fontanelle was constructed and fontanelle pressure measurements were recorded at varying forces of application of the sensor. This in vitro technique demonstrated that anterior fontanelle pressure measured with the Ladd monitor is dependent on the force of application. Measurements of anterior fontanelle pressure were made in 17 infants and were correlated with simultaneous direct intracranial pressure measurements. These in vivo measurements confirmed the findings on the artificial fontanelle. Both the in vivo and in vitro measurements suggest that an application force of 7 to 10 gm on the sensor will produce an accurate reflection of intracranial pressure. We describe two devices with which the sensor may be applied to the fontanelle with constant measurable force: one for intermittent measurement and another for continuous recording.