Pre-auricular swelling and malocclusion.

Accepted 15 September 1997 A 58-year-old man was referred to the Head and Neck Clinic for the diagnosis and treatment of a painless swelling in the left pre-auricular region of approximately 18 months duration. The swelling had appeared suddenly and had remained the same size until one month prior to his referral when the swelling abruptly increased in size and then slowly decreased to its original size following two courses of nonsteroidal anti-inflammatory drug (NSAID) therapy. There was no history of joint trauma, pain or joint locking. Loading of the joint during eating and talking did not produce any joint symptoms, but the patient noted that his 'bite' did not feel perfect. The medical history was unremarkable and specifically, there was no history of disease involving any other joints. Physical examination showed a firm, non-tender 3.0 x 3.0 cm swelling anterior to the left ear. There was moderately limited translation of the left condyle and a slight deviation of the mandible to the left during mouth opening. The patient had an active mouth opening of 40 mm interincisally and a mild crepitus was heard during auscultation of the left temporomandibular joint. The patient had a mild malocclusion characterised by a slight left posterior open bite with a mild anterior shift of the left mandible. A computed tomography (CT) scan indicated that the lesion originated within the left intra-articular space and showed a poorly defined peripheral soft tissue component completely encircling the head of the condyle. The mass had displaced the condylar head anteriorly and inferiorly (figure 1).' There was no involvement of the parotid gland. The patient was taken to the operating theatre where the left temporomandibular joint was explored using a pre-auricular approach. The joint capsule was markedly distended and a thick synovial fluid was apparent as the superior joint space was entered. A white, gritty, dough-like mass measuring 3.0 x 2.0 cm was removed from the anteromedial aspect of the upper joint space. The inferior joint space was carefully examined and no additional masses were found. The condylar head was covered with normal looking fibrocartilage. The articular surface was rippled and smooth but markedly flattened. There was no evidence of erosive disease or osteophyte formation. The meniscus appeared normal in colour and texture. There was no evidence of perforation. Histologic examination of the specimen by polarized light microscopy demonstrated positive birefringent, parallel lipid crystals (figure 2).2 Scanning electron microscopic (SEM) analysis demonstrated rhomboid and rod-like crystals ranging in size from 1 to 5 gm (figure 3).3 Infraredspectrophotometric analysis (IRSA) was also carried out.