Introduction : Orbital roof blow-in fractures without involvement of the vertical portion of the frontal bone are a rare entity in the adult population. Mechanisms of this fracture pattern often remain unclear.

Case report : A 22 year-old male presented with a cranioencephalic trauma secondary to a road traffic accident. Brain damage meaning an intraparenchymal haemorrage occurred at the right frontal lobe base, leaving no sequelae. Several cranial base and vault fractures were present (longitudinal fracture of the petrous portion of both temporal bones, and fracture of squamous portion of right temporal bone). As facial fractures, he only presented with a right orbital roof blow-in fracture, thus, ipsilateral to the fractured temporal bone squamous portion. Severe right eye proptosis and muscular entrapment was present, although visual acuity was preserved. In CT Scan, a free fragment of the right orbital roof was impacted against the superior rectus muscle underlying a moderate hematoma. Patient was operated under general anesthesia removing both hematoma and bony fragment. Solution of continuity in the frontal bone base was patched using a PLA/PGA implant, placed passively between superior periosteum and rectus muscle. This manoever mitigate the possibility of brain herniation through the bone leading to an orbital encephalocele.

Discussion : Frontobasal and cranial Vault trauma mechanisms are often very complex, involving both facial and cranial base buttresses. In this particular case, orbital roof fracture might have been produced by energy transmission through fractured petrous portions of both temporal bones. This theory did not satisfy the authors, since there were no other frontobasal fracture lines. We tried to explain the findings through a blow-out mechanism of the anterior cranial fossae. Ipsilateral fracture of squamous portion of the temporal bone, and brain damage near to the site of orbital fracture support this theory.