Complete transverse basilar cleft associated with hemifacial microsomia.

Transverse basilar cleft (TBC) is an extremely rare variation of the clivus or the basilar part of the occipital bone. In this report, a unilateral transverse basilar fissure was found at the clivus in a head computed tomography of an 18-year-old female patient diagnosed with hemifacial microsomia (HFM). Image analysis of this patient showed shortening of the ramus of the right mandible along with medial displacement of the right temporomandibular joint and hypoplastic right maxilla. In addition, observation of the clivus showed a cleft between the basioticum and basioccipital bones at the level of the pharyngeal tubercle on the right side. This cleft was identified as TBC. Clival variations, TBC included, attributed to HFM have never been reported. This report draws attention to the complex relationship between abnormal development of clivus and HFM syndrome, and sheds light on a possible genetic and molecular association between these two conditions.