Osteolysis circumscripta evanescans.

A circumscribed radiolucent skull abnormality was detected on plain radiographs obtained to evaluate minor cranial trauma in a young boy. The lesion disappeared on follow-up X-rays performed later in the day. Analysis of the case revealed that the lesion was an artifact resulting from a superimposed hole in a wooden backboard on which the patient was X-rayed initially. Radiographs shot through a protective backboard may be misleading, and not all abnormalities identified belong to the patient.