[Skull fracture or accessory suture in a child?]

Differentiation between accessory sutures and fractures in the skull of an infant can be difficult. Apart from the regular sutures there is a multitude of variations that may be mistaken for a fracture line. Such variations include for instance the intraparietal suture between the two ossification centers of the parietal bone or the mendosal suture between the supraoccipital and interparietal bone of the occipital squama. The presented case refers to an approximately 20-month-old female child. During autopsy, a discontinuity in the right paramedian posterior cranial fossa parallel to the internal occipital crest with connection to the foramen magnum was observed. The macroscopic findings suggested a fracture line because of its course. However, neither a hemorrhage in the soft tissue nor callus formation was discernible. The discontinuity was preserved with the adjacent parts of the occipital bone for further histological examination. In the report of a cranial CT, which was carried out five days before the child's death, an accessory suture paramedially in the right posterior cranial fossa was described. When the clinical CT records were re-evaluated, a similar discontinuity at the corresponding position on the other side was detected, though of noticeably shorter length. Additionally, the preserved occipital bone fragment including the discontinuity was histologically processed. In the radiological literature, precise (radiological) criteria for differential diagnosis are indicated. A zigzag pattern with sclerotic borders and a bilateral and fairly symmetric occurrence indicate a suture, whereas a sharp lucency with non-sclerotic edges and a unilateral occurrence indicate a fracture. Taking all the findings into account, the depicted discontinuity was regarded as an accessory suture. This case demonstrates that differentiation between a fracture and an accessory suture may be difficult in the autopsy of a child and underlines the importance of a postmortem CT examination.