Paget’s disease of the temporal bone
What is Paget’s disease of the temporal bone?
Paget’s disease of the temporal bone is a rare hereditary and chronic condition that can lead to hearing loss and dizziness. Paget’s disease of bone (osteitis deformans) is the abnormal break down and new formation of bone. This process leads to weak, soft and porous bone. It can affect different bones in the body and when it affects the temporal bone it is referrred to as Paget’s disease of the temporal bone.
Who get Paget’s disease of bone?
It is estimated to occur in 3% of patients older than 40 years and increases with age.
It is more common in males. Although the exact cause is not known, genetic factors in combination with some environmental factors are suspected to play a role. The abnormal genes are likely the reason why family members of an affected individual are more likely to develop it. It is unlikely caused by a virus infection, as believed by some. Paget’s disease of bone is more commonly seen in Central Europe, the United Kingdom and countries where people from these areas have settled. In South Africa the prevalence is 2,4% in patients older than 55 years (Guyer 1988).
Which bones are most commonly affected?
Paget’s disease of bone can be confined to one bone of the body in 15% of patients and is then referred to as the monostotic variety. This type seldom affects hearing and balance. More commonly it affects more than one bone and is then referred to as the polyostotic variety. This type can affect the temporal bone of the skull in 65-70% of cases. Besides the skull, the bones most commonly affected include the spine, the pelvis and the long bones of the extremities.
Symptoms of Paget’s disease of bone.
Most patients with Paget’s disease will have no symptoms. The most common symptom is pain in the affected bone/bones. Nearby joints may also be painfull. The new weaker bone may cause deformities and fractures. The spesific symptoms will depend on which bones are affected. Other symptoms include tingling and weakness in extremities. Nerves can also be pinched by the abnormal bone. Luckily the facial nerve is not commonly involved.
Pagets disease of the temporal bone and hearing loss.
Paget’s disease may present with unexplained hearing loss, especially in one ear. In patients with skull involvement, 30-50% may experience hearing loss. According to Deep and co-workers (2017) the most common pattern of hearing loss is a down-sloping, high frequency sensorineural hearing loss, often with a low frequency conductive loss. It is typically bilateral and progressive, occuring at a rate that is greater than observed in age-matched healthy patients. The exact mechanism of hearing loss is not known. Tinnitus occurs in 20% of patients with Paget’s disease of the temporal bone and is believed to co- incide with the hearing loss. Tinnitus may be pulsatile in nature.
Paget’s disease of the temporal bone and vertigo.
Dizziness is reported in 52% of patients in the series by Deep and co-workers (2017). True vertigo is rare with generalized imbalance being the norm. As with hearing loss the mechanism of vertigo and imbalalance is poorly understood.
Complications of Paget’s disease of bone.
Paget’s disease of bone may lead to deformities, fractures, pinched nerves and osteoarthritis. The facial nerve is rarely affected. Heart failure may develop in some patients due the fact that the heart must pump harder to get the blood through the affected bone. Bone cancer may develop in 1% of patients with Paget’s disease of bone.
How is Paget’s disease of bone diagnosed?
After clinical examination it is likely that an X ray, computed tomography (CT) scan, and in some cases a magnetic resonance (MR) imaging of the affected area be ordered.
There are other bony conditions, such as fibrous dysplasia (FD) that may look like Paget’s disease of bone on imaging. Blood tests will show an increase in alkaline phosphatase, an enzyme found in bone. Radio isotope studies will demonstrate other affected areas in the body an may be requested if whidespread involvement is suspected.
Treatment of Paget’s disease of bone.
Not all patients may require active treatment. In asymptomatic patients follow up will usually be advised. Depending on the activity, severity and site of the involvement, treatment may be necessary even if a patient is not symptomatic. This is indicated in a preventative sense, to avoid later complications. The medical treatment of choice is biphosphonates, commonly used in osteoporosis. It may cause side effects in which case calcitonin, a natural occuring hormone in calcium metabolism, may be used as an alternative. Surgery may be indicated in patients with fractures, joint problems, deformed bones and in those where nerves are compressed. Surgery may improve hearing loss and some patients may benefit from bone conducton hearing devices such as the BONEBRIDGE from MED-EL and the PONTO or even cochlear implantation (CI).