Magnetic and Impedance Measurements for the Detection of Spreading Depression at a Distance

3. With neurosurgical exposure of vulnerable brain tissue, the monitoring of disturbances such as SD beneath the surface, causing local changes of electrical impedance, may be carried out through the application of current and the measurement of voltage changes restricted to the tissue surface. 4. In neurosurgical monitoring an important distinction must be made between mild superficial disturbances and deeper profound disturbances, which in some respects produce similar signals at the surface. Information about the depth of the disturbance can be extracted from multiple surface impedance measurements, and may assist in making this distinction.