Residual foreign bodies in the neck might result in life-threatening complications. This patient presented with a delayed rupture of the CCA and IJV, subcutaneous emphysema, pneumomediastinum, and hemopneumothorax. The residual foreign body might damage the tunica media with intact adventitia, and lead to the formation of a pseudoaneurysm. Presentation can be delayed for several days, and is usually with a hematoma and pressure symptoms because of minor bleeding . Severe bleeding from arterial damage is catastrophic and is even fatal . Moreover, the hematoma might compress and displace the trachea, causing airway obstruction or choking. In this case, the foreign body pierced the right cervical pleura, causing air to leak through the perforation into the mediastinum and pleural space.
Two underlying mechanisms might account for the delayed rupture of the CCA and IJV caused by this residual foreign body. The action of swallowing or violent coughing might have induced the migration of the sharp broken chopstick close to adjacent vessels, and its tip pricked into the vessel wall. In addition, the residual chopstick could have caused the formation of a pseudoaneurysm, which eventually led to the massive bleeding from the delayed rupture of the neck vessels.
The residual broken chopstick was not detected until continuous bleeding was manifest, with a delay of three days from injury to definitive diagnosis. This delay should be attributed to two facts. First, the patient did not provide a detailed history of the trauma. The possibility of a residual foreign body was not taken seriously because the mild stab wound only exhibited slight bleeding and no hard objects were palpated by physical inspection. Second, the doctor did not emphasize the occurrence of subcutaneous emphysema on the first visit, and CT scanning of the chest was not performed. As a result, no efforts were made to discover the reason for the hemopneumothorax that was caused by the neck trauma.
Detection of wooden foreign bodies is difficult from a plain X-ray. In this case, a plain X-ray of the neck did not reveal the foreign body impacted in soft tissue. This was probably due to the fact that there was similar transmitted light under X-ray between the wooden object and nearby soft tissue. A radiopaque foreign body might be obscured by the opacity of cervical vertebrae, resulting in the disappearance of the foreign body on a common radiograph. Kantarci et al.  reported that the entry of a wooden foreign body into the neck was detected neither in the emergency department nor during conventional radiograms. CT scanning has been demonstrated to be an effective imaging modality in detecting wooden foreign bodies. The cross-sectional view on CT imaging is beneficial in determining the location of the foreign body and its relationship to vital structures in the neck . Sonography is a useful modality in detection and localization of radiolucent foreign bodies in soft tissue which can avoid misdiagnosis during primary emergency evaluation . Jacobson et al.  demonstrated that ultrasound can effectively locate 2.5mm-long wooden foreign bodies with a sensitivity and specificity of 86.7% and 96.7%, respectively. The sensitivity and specificity of ultrasound for the detection of 5.0mm-long wooden foreign bodies has been demonstrated to be 93.3% and 96.7%, respectively . The early detection of a residual foreign body eliminates the risk of the delayed rupture of a vessel.