[A new procedure for removal of foreign bodies in the area of the head].

Identification and extraction of penetrating cranial foreign bodies can cause problems in some cases. Small fragments localized deep in the orbit or cerebrum can be especially hard to detect. Severe bleeding and traumatized anatomy can make orientation difficult. We used a new localizing device, computer-assisted surgery (CAS), to good effect in six such cases. CAS is a localizing technique designed to assist the head surgeon during surgery, providing real-time position information. The method is based upon a three-dimensional volume model of the patient's skull generated by preceding computed tomography imaging procedures (CT or MRI). Intraoperative correlation of a 3D-model and the patient's skull allows for real-time position display of a surgical instrument on the monitor screen. Thereby the surgeon is able to localize even small foreign bodies without extensive exploration. In the case of multiple foreign bodies the surgeon calls up a simple documentation facility recording which of the visible fragments have already been extracted. We successfully used the system for extraction of orbital foreign bodies in four and intracerebral foreign bodies in two cases. In a 4-year-old child with gunshot injury the bullet was located in the precentral region and was easily extracted with the CAS system. In a 21-year-old man 39 glass fragments were extracted from the left orbit. In a 36-year-old man a bone fragment was dislocated to the apex of the orbit directly under the optic nerve. Location and extraction were achieved without damage to the orbital structures with the help of the CAS system.