Brachial plexus injury is a peripheral paresis with the incidence that varies from one to two cases for every 1000 live births. It involves injury to any nerve of the brachial plexus during a birth. The consequence of this complication can usually be the reduced mobility of the upper limb or its part when the rehabilitation process is not done properly. Muscle action is the most important source of increased metabolic heat. Long-lasting injuries appear on thermogram as hypothermic areas which may be caused by reduced muscle contraction, and therefore reduced heat production, which should be possible to observe using the Infrared Thermography Imaging (IRT).