A cephalhaematoma and maybe more, a tricky diagnosis

Abstract

BACKGROUND: Cephalhematomas are fairly common occurrences in children who have undergone traumatic births. These often result in ultrasound requests in order to rule out central nervous system damage.

CASE PRESENTATION: We present the case of a 13-day-old boy with a large cephalhaematoma who was referred for a transfontanellar ultrasound. The ultrasound exam revealed a cephalhaematoma with what appeared to be a large extra-axial collection on the other side of the of the skull, opposite to the site of the cephalhaematoma. An MRI was performed to confirm the finding, revealing the collection to be caused by the mirror image artefact.

DISCUSSION: The mirror image artefact is caused by the delayed return of ultrasound waves due to multiple reflections before reaching the ultrasound probe. This can cause the appearance of some images to be repeated and found in abnormal positions when the signal is interpreted and displayed on the screen. This is an important artefact to be aware of as it may cause images to be misinterpreted and cause unnecessary alarm, all the while making it very difficult to outright dismiss the possibility of the image being real, posing a diagnostic dilemma for the radiologist.

The existence of the mirror image artefact once again shows that ultrasound, though undeniably useful, can be fraught with challenges. Knowledge of these artefacts is important yet does not necessarily allow the radiologist to differentiate between a real image and an artefactual one.