Abstract
This report presents the case of an extensive synovial chondromatosis of the temporomandibular joint (TMJ), with extension into the middle cranial fossa, middle ear, and carotid canal. Synovial chondromatosis of the TMJ is rare, particularly when associated with intracranial involvement. This case is unique owing to its size and the involvement with the internal carotid artery. The importance of a multidisciplinary approach in the surgical management of such a rare and complex form of this condition is highlighted.
Synovial chondromatosis is defined as a benign, nodular, cartilaginous proliferation arising from joint synovium, bursae, or tendon sheaths. The cartilaginous nodules that characterize the disease may detach from the synovial membrane, becoming loose bodies within the joint space . Loose bodies, however, are not always detected. The condition usually affects the long bones of young adults and is infrequently seen in the temporomandibular joint (TMJ). When associated with the TMJ, it most commonly presents in middle-aged females. Pain, swelling, and altered jaw function are the most common presenting signs and symptoms. Sensory disturbances are an unusual presenting complaint . The aetiology of the condition is not well understood. A primary form appears to exist that has no causative factors, and is thought to behave in a more aggressive manner. A secondary form may result in reactive metaplasia after trauma or prolonged joint disease. It is, however, relatively uncommon for a patient with synovial chondromatosis to have had a preceding trauma .
Case report
A previously healthy 34-year-old male was referred by his general medical practitioner with a right-sided bony hard pre-auricular swelling, which had been gradually increasing in size over a 5-year period. He complained of ipsilateral hearing loss for 2 years. Interestingly, he did not complain of pain, limited mouth opening, or altered occlusion. He had sustained a fracture of his right mandibular condyle approximately 10 years prior to presenting with facial swelling, which had been managed conservatively.
Clinical examination demonstrated a well-defined, non-tender, firm swelling in the right pre-auricular region, which measured approximately 3 × 5 cm. A panoramic radiograph showed a large mixed radiopaque mass overlying the right condyle, extending superiorly ( Fig. 1 ). The condyle itself was not deformed. A computed tomography (CT) scan revealed an irregular, partly calcified lesion surrounding the right condyle, measuring 4.5 × 3.7 cm. Superiorly, the mass had resulted in complete erosion of the floor of the right middle cranial fossa, causing indentation of the inferior and occipitotemporal gyri. Additionally, there was erosion of the lateral wall of the carotid canal. The middle ear cavity was completely opacified with some erosion of the middle ear cavity/external auditory meatus caused by the mass. Subsequent magnetic resonance imaging (MRI) revealed the mass indenting the pterygoids, but without muscular invasion ( Fig. 2 ).
The differential diagnosis based on these findings included chondroblastoma, osteochondromatosis, pigmented villonodular synovitis, and synovial chondromatosis. Given the atypical and extensive appearance of the lesion, an open biopsy was arranged. Histopathological analysis confirmed multiple variously confluent nodules of hyaline cartilage with variable myxoid change, increased cellularity, prominent cytological atypia, and surface calcification. Atypical features included nuclear enlargement, pleomorphism, focal hyperchromatism, and multiple nuclei. Calcification extended to the adjacent fibrous synovial capsule. A diagnosis of synovial chondromatosis was made. Following neurosurgery input, magnetic resonance angiography (MRA) was arranged to allow for surgical treatment planning.
Surgery was undertaken by oral and maxillofacial surgeons, with support from ENT and neurosurgeons. The tumour was approached via a pre-auricular incision with temporal extension. The zygomatic arch was osteotomized in order to optimize access, which was further aided by a condylotomy. The mass consisted of a semi-solid, gelatinous material ( Fig. 3 ), and was excised by piecemeal resection. Although preoperative imaging raised the suspicion of dural penetration, it was possible to separate it from the dura with the aid of an operating microscope, without causing a dural leak. Furthermore, macroscopic disease was resected from the internal carotid artery as it was judged to be safe intraoperatively. The preoperative MRA demonstrated an incomplete circle of Willis, therefore sacrificing the internal carotid artery may have resulted in a neurological disability. As synovial chondromatosis is a benign, metaplastic entity, it is not considered essential to completely excise it if this would put vital structures at significant risk. A temporalis muscle flap was utilized to cover the resultant defect.
The patient made a good recovery, initially sustaining only frontal branch of facial nerve weakness and paresthesia of the right pre-auricular distribution. These have since almost completely resolved. His right-sided hearing problems have also resolved and postoperative mouth opening is improving with physiotherapy. A postoperative CT scan showed minimal residual tumour on the posterior and medial aspect of the original lesion ( Fig. 4 ). The patient is due to be reviewed in the coming weeks for his one year follow up. A further CT scan has been arranged for the one year review appointment to monitor his progress and residual disease. He will need to be reviewed yearly indefinitely, with an MRI initially every 2 years for 6 years, then three-yearly following that.
