Neurosurgical stimulation, impedance monitoring and data acquisition system.

We describe the design of a programmable neurosurgical stimulator with impedance monitoring facilities. The computer is used both to control a stimulator and for the storage of various parameters employed in the process. The stimulator is designed to minimize tissue damage by injecting net zero charge; its output is a current, independent of load resistance. By measuring electrode voltage, the load impedance can be calculated. Software is provided in order to log patient data, and trajectory details with reference to coordinates calculated from other imaging systems such as CAT scanners.