Incidence of intracranial bullet fragment migration.

Migration of retained bullets or bullet fragments may present as a complication of gunshot wounds to the head. This phenomenon has been reported in cases of abscess formation or retained copper fragments. Management of such migratory fragments is controversial. The purpose of this study is to determine the incidence of fragment migration in a population of neurosurgical patients treated for gunshot wounds to the head. Two-hundred and thirteen cases treated at Detroit Receiving Hospital between 1985 and 1987 were reviewed. Each patient treated had initial and one week follow-up imaging studies. Nine cases of documented migratory intracranial bullet fragments were identified. Thus, the incidence in this population is 4.2%. The fragments in eight cases were composed of copper, and in the remaining case, lead. No case was associated with an abscess. Fragments in the anterior fossa were found to migrate towards the sella turcica, while those of the middle fossa and posterior hemispheres migrate towards the confluence of sinuses (Torcula Herophili). Fragment migration was documented as early as 36 h post-injury. Based on this study, we recommend serial imaging studies to look for migrating bullet fragments and surgical removal aided by intra-operative ultrasound to localize the fragment when possible.