Abstract: The invention relates to a sensor device for detecting changes in location and position of a proband in a neuronavigation system which is used to carry out and support surgical interventions. Said device can be fixed to the head of the proband and the output signals are supplied to a system computer as correction data. According to the invention, a shaped tooth rack for receiving a fixing agent and a sensor capsule with means for detachably fixing to the tooth rack are provided. The shaped tooth rack is fixed in the oral cavity of the proband with the fixing agent, the sensor capsule being oriented towards the outside in the direction of the cheek so that the oral cavity remains essentially free.