UNUSUAL PATHOLOGIES AFFECTING THE TEMPOROMANDIBULAR JOINT
Authors: Loughlin, A., Annan, D., Makdissi, J., Adams, A.
Temporomandibular joint (TMJ) pain is a common clinical complaint in the Primary Care setting with an estimated 26% of the population complaining of oro-facial pain1. On the occasions when imaging of the TMJ is indicated, unusual findings can be unearthed. This is a selection of the more unusual pathologies affecting the TMJ observed in a London Hospital. It is crucial that the more aggressive conditions are readily diagnosed and appropriate treatment commenced due to the high morbidity associated with lesions of the TMJ due to the anatomical proximity to the middle cranial fossa and and temporal bone.
Gout arises when supersaturation of tissues with urate occurs. This leads to the formation of monosodium urate crystals in and around joints. Gout is classified as a metabolic arthritis and has four stages; asymptomatic hyperuricaemia, acute gouty arthritis, intercritical gout and chronic tophaceous gout. Rarely, gout may affect the TMJ and may lead to its destruction2.
Demographics: Common joint disease affecting 1:40 people in the UK. Gender ratio 4:1 (M:F). Gout can affect men of any age but is rare in pre-menopausal women. The incidence of gout increases with age from age 20 with a plateau over 80 years3.
Radiological features: May include general signs such as lysis of the condyle, effacement of the normal architecture and loss of cortical definition2. In cases with subcortical cysts without erosion, intrasynovial/juxtasynovial masses and where there are multiple radiopaque foci within a mass extending beyond the confines of the joint, gout should be considered4.
SICKLE CELL DISEASE
This is a group of disorders which affects haemoglobin which in turn alters the shape of the red blood cells and may result in vascular occlusion. The low blood flow within bone increases the potential for vaso-occlusive crisis. Bone marrow hyperplasia occurs in response to increased demand for haemopoietic tissue. There are also bony changes associated with ischaemic events- if the ischaemia involves the joints, a septic arthritis may occur.
Demographics: 1:4600 people living in the UK have sickle cell disease making it the most common inherited disease5. It is more common in people of African and Afro-Caribbean origin and is increasing in prevalence in the UK because of immigration into the UK and new births6.
Radiological features: Radiographically sickle cell disease may be obvious as osteopenia of the mandible and thinning of the bony cortices. Bone and joint areas affected by hypoxia may initially cause bone hypervascularization and significant inflammatory processes visible as hyperintense in MRI in T2. Persistent hypoxia and inflammation result in aseptic bone necrosis which appears as hypointense signal in T2.
TB is a chronic granulomatous disease caused by bacterial infection with Mycobacterium tuberculosis. TB commonly affects the lungs but may also affect extrapulmonary sites and nearly 10% of all extrapulmonary sites are maxillofacial manifestations7. Tuberculous osteomyelitis of the mandible forms less than 2% of all skeletal TB8.
Demographics: There were 9.2 cases of TB per 100,000 in the UK in 2017. People born outside the UK account for 71% of TB notifications. This is 13 times higher than in populations born within the UK. Co-infection with HIV affects 2.8% of TB sufferers9.
Radiological features: MRI features of TB infection in the peripheral joints can show synovitis, joint effusion, bone resorption and abscess formation. This case demonstrates an expansive lesion with destruction of the condyle and fossa without alteration of the disc. There is a subcutaneous mass adjacent to the parotid gland with a liquid like centre and resorption of the condylar head.
ANKYLOSING SPONDYLITIS (AS)
AS is an inflammatory arthritis where there is long term inflammation of the joints of the axial skeleton. Occasionally other joints can be involved with involvement of the TMJ being reported in 10-24% of cases10. AS affects the synovial and cartilaginous articulations and the sites of tendon and ligament attachment to bone. In patients with AS, gross restriction of mouth opening along with pain in the TMJ may occur.
Demographics: AS usually presents in the 3rd decade of life and rarely presents after 45 years. The prevalence of AS is 0.1-1.4% of the global population. Within Europe, there is an incidence of 18.6 cases per 10,000 population (<0.01%). AS affects males more commonly than females with a gender ratio of 3.8:1 (M:F) in European populations11.
Radiological features: On radiological investigation, AS may present as massive deformity and severe erosion of the condyle.
Hyperparathyroidism is the effect of excess parathyroid hormone (PTH) on the body and is classified as either primary (caused by a problem with the parathyroid glands), secondary (caused by chronic hypocalcaemia usually related to renal disease) or tertiary (where chronic overstimulation of the parathyroid gland in secondary hyperparathyroidism causes autonomous parathyroid hyperfunction). There are multiple systemic effects of hyperparathyroidism including bone pain related to osseous demineralisation, abdominal pain due to renal calculi and psychiatric disturbances12.
Demographics: Tertiary hyperparathyroidism affects patients who suffer from secondary hyperparathyroidism. It is most commonly seen in patients who have undergone renal transplantation and have a persistent hypercalcaemia12.
Radiological findings: There are a range of radiological findings associated with hyperparathyroidism. Osteopenia and osteosclerosis, soft tissue calcifications, subperiosteal bone formation and subchondral resorption. Within the maxillofacial region; loss of the lamina dura may be seen. Brown tumours (multilocular radiolucent areas) and ossifying fibromas of the jaws (encountered in hyperparathyroid jaw tumour syndrome) may also be demonstrated13.
SKULL BASE OSTEOMYELITIS
Osteomyelitis is an infection of the bone. It is not uncommon to develop osteomyelitis in the mandible from odontogenic causes however the tooth bearing portion of the mandible is the commonly affected site. TMJ osteomyelitis however is a rare finding and carries with it significant morbidity. Condylar infections are usually haematogenous in origin14.
Demographics: Extremely rare; approximately 20 cases reported in literature14. The age range was from 14-82 years with no gender predilection. Risk factors include chronic systemic disease, alteration in bone vascularity and immunocompromise (diabetes mellitus, malignancy, HIV/AIDS) however 60% cases without a noteworthy medical history.
Radiological findings: Irregular bony resorption of the condyle and skull base. Opacification of the mastoid air cells. Loss of the normal soft tissue architecture in the region of the infratemporal fossa.
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