Synovial chondromatosis (SC) is an uncommon disorder that primarily affects large joints, with a predilection for knee, hip and elbow joints. Cartilaginous nodules form within the sub-synovial membrane and may detach, forming loose free-floating, sometimes calcified, bodies within the joint space. It is progressive and does not undergo spontaneous resolution. SC may rarely affect the Temporomandibular joint (TMJ). The disease is usually confined to the superior joint space but it may erode the mandibular condylar head or the floor of the middle cranial fossa, destroy the temporal skull base and/or invade the intracranial structures. Intracranial extension, as occurred in our case of SC, is extremely rare.

The diagnosis is made on the basis of imaging and histology. Differential diagnoses include osteoma, osteoblastoma, osteochondroma, condylar hyperplasia, chondroblastoma, chondrosarcoma, and osteosarcoma. Complete excision is the treatment of choice since incomplete removal may result recurrence.

In this presenting case, surgery was performed as a combined procedure with a neurosurgeon. Superior joint space was approached via a pre auricular incision. Surgical access was enhanced by dividing the zygomatic arch and performing an osteotomy of the condylar neck at the sigmoid notch. Attachment of the lateral pterygoid muscle was preserved. Bony defects in the cranial base were filled with “Norian SRS Fast Set Putty”. Condylar head and zygomatic arch were reduced and fixed with mini-plate osteosynthesis.

Conflict of interest: None declared.