Introduction of skull bone fragments into the brain during external ventricular drain placement

To report an observation of small high attenuation foci in the tract of external ventricular drain on computed tomographic (CT) scan after removal of the drain and propose an explanation for this observation.

Six patients with small high attenuation foci in the ventricular drain tract seen on CT after removal of the drain were retrospectively identified. The CT studies before, during, and after ventricular drainage were reviewed for the size, shape, location, and time of appearance of these foci.

In all patients, the high attenuation foci in the drain's tract were identified on CT done within 24 h from removal of the drain. In one patient, the high attenuation focus was seen adjacent to the drain on the CT obtained while the drain was in place. The high attenuation foci maintained constant size and shape on serial follow-up CT, and had variable location along the drain's tract. None of the patients developed symptoms related to these foci.

Small bone pieces from the calvarium after drilling for external ventricular drain can inadvertently be pushed into the brain parenchyma during drain insertion. Early identification of these pieces on CT after removal of the drain and their constant size and shape are the clues for their nature. Temporal evolution of CT findings does not support the possibility of calcification in a small infarction or hematoma in the tract of the drain.