Apparatus for detecting intracranial temperature and blood oxygenation includes a transducer having a working surface for placement against a patient's cranium. The transducer forms a microwave antenna having walls defining an aperture having a pair of opposite broader boundaries and a pair of opposite narrower boundaries at the working surface. The antenna is tuned to a frequency which produces a first output signal indicative of heat emanating from the cranium. An oxygen saturation sensor sharing that aperture includes a radiation emitter located at one of narrower boundaries which directs electromagnetic radiation across the aperture to a radiation detector at the other of the narrower boundaries and which produces a corresponding second output signal. A control unit includes a display and a processor for processing the signals to calculate an intracranial temperature and an oxygen saturation value for display by the control unit.