We reported a clinical case of an roentgen negative foreign body in the right temporal lobe of the brain in a patient with a penetrating craniocerebral injury which mimicked pneumocephalus.

Materials and methods. A man, 36 years old, was referred to the A.I. Burnazyan Federal Medical Biophysical Center to continue treatment for concomitant head and chest trauma. From the history it was known that 2 weeks ago penetrating cranioorbital head injury by a wooden stick happened, which was completely removed during the initial surgical treatment. According to computed tomography in the right temporal lobe of the brain a pathologic area with a density corresponding to the gas, -890HU, was noted, which differentiated between the wound canal filled with air and an  roentgen negative foreign body. Magnetic resonance imaging data did not provide additional information. An experiment was carried out in which it was demonstrated that a dry branch can have a gas density, in particular, - 850HU. Based on the history, the duration of the injury, the shape and the contours of the pathological area in the right temporal lobe, the final conclusion was made about the presence of a foreign body in the brain, which was confirmed during surgery.