A 74-year-old man complained of having hearing difficulties and a blockage in his ear. He has a history of chronic ear drainage. Two years ago, he had a procedure to drain the infection from his right ear. Since then, he has had continuous ear drainage. He also reported feeling pain and warmth in his ear, and noticed that his hat size had become a little bit larger. He was otherwise healthy, and has not had previous surgery. Examination of his ear showed copious pus and debris in the ear canal. His audiogram is on the right (Fig. 1).
Diagnosis: Paget's Disease
The patient's CT scan showed an abnormal bone growth in the skull that involves the temporal bone (Fig. 2), indicating that he had Paget's disease of the skull. Paget's disease is a hereditary bone disorder characterized by involvement of the skull, spine, pelvis, and long bones of the extremities. It affects approximately three percent of people over 40 years old. The increased bone turnover makes the bone fragile. When the long bones are involved, patients are at risk of a fracture.
Early in the process of Paget's disease of the temporal bone, patients may feel some warmth and/or pain in the skull area. As the disease progresses, many patients get headaches. The disease can sometimes lead to narrowing of the external auditory canal, which results in chronic otitis externa. In this case, the patient likely had a canalplasty or canal wall down mastoidectomy for chronic otitis externa. However, he had continued drainage due to irregular bony growth. About a third of patients with skull involvement usually develop increased skull circumference and notice that their hat size has increased, like what happened with this patient.
The most common pattern of hearing loss is a down-sloping, high-frequency sensorineural hearing loss that is often in conjunction with a low-frequency conductive loss.
Hearing loss among patients with Paget's disease of the temporal bone is generally bilateral and progressive. It also occurs faster than in the general age-matched population. The rate of hearing loss in patients with this condition is approximately 2 dB per year. This patient had conductive hearing loss on the right side, but the left side was unaffected (Figs. 1 and 2).
Paget's disease is either monostotic (single-bone involvement) or polyostotic (multiple-bone involvement). The polyostotic form involves the skull in 65 to 70 percent of patients. In patients with skull involvement, 30 to 50 percent have hearing loss and 20 to 25 percent have vestibular dysfunction (Ann Otol Rhinol Laryngol. 1975;84:1; Lancet. 1956;271(6933):51).
Demineralization of the petrous apex is often seen on CT imaging. Decreased density of the petrous bone with bony expansion often occurs (Fig. 3). Unlike fibrous dysplasia, Paget's disease normally involves the dense otic capsule. The normal otic capsule bone is very dense and appears white on CT imaging. The otic capsule can be involved in Paget's disease in approximately 56 percent of the temporal bones (see Figs. 4 & 5; Otol Neurotol. 2017 Jul;38(6):907). Narrowing of the internal auditory canal can be seen in patients with severe otic capsule involvement (Fig. 6). The ossicles can be involved in some patients. This causes conductive, sensorineural, or mixed hearing loss. Some patients have successfully undergone cochlear implantation (CI) for hearing loss due to Paget's disease, though CI candidacy among this population is rare (Laryngoscope. 2011 Feb;121(2):358).
Medical treatment of Paget's disease is tailored to its symptoms. Asymptomatic patients are observed, while those with headaches can be treated with nonsteroidal anti-inflammatory drugs such as ibuprofen. Patients with cranial neuropathy from compression or progressive bony deformity may require further treatment. For these patients, bisphosphonates are the first-line therapy that reduces the increased rate of bone turnover. Calcitonin, which can inactivate osteoclasts (bone cells that cause destruction/resporption of bone), is used in the treatment of patients with aggressive Paget's. External canal narrowing can be treated with alcohol/acetic acid irrigations. Later, after significant stenosis, surgery can be done to widen the canal.
Treatment of hearing loss in Paget's disease has been performed with calcitonin alone or in combination with etidronate. These approaches have been found to stop the progression of hearing loss in some patients with Paget's disease of the temporal bone (Arch Otolaryngol Head Neck Surg. 1988;114(8):891). Many patients develop progressive bilateral mixed hearing loss that eventually leads to total deafness despite medical interventions. Stapedectomy has not been very successful in treating conductive hearing loss in these patients, but bone-anchored hearing aids have been used with much success. CT imaging is also beneficial in finding the best place for an osseointegrated implant and avoid the demineralized cortex affected by the disease.
Several mechanisms have been considered to cause hearing loss in patients with Paget's disease. Hearing levels have been reported to be closely associated with cochlear capsule bone mineral density, which suggests that local changes in the cochlear bone may lead to hearing loss. Other possible mechanisms for the sensorineural hearing loss in Paget's disease of the temporal bone include damage to cochlear hair cells, microfractures, compression or stretching of auditory nerves due to new bone formation around and within the internal auditory canal, or as a result of basilar invagination, spiral ligament degeneration, endolymphatic hydrops, or vascular shunts created by the hypervascular pagetic bone (Otol Neurotol. 2017). The mechanisms that have been thought to cause conductive loss include ossicular fixation from a low-hanging tegmen from an abnormal bone growth that abuts the ossicles in the epitympanum, fibrous fixation of the ossicles, distortion of the oval window that dislodges the stapes footplate from its normal position, or round window obliteration. Pulsatile tinnitus may also occur due to conductive hearing loss or the presence of large vascular channels in the new bone, among others. The facial nerve is generally not involved in Paget's disease, though rare bouts of facial spasm have been reported.
Paget's disease is diagnosed by serum testing in combination with radiographic imaging (x-rays or bone scans) to check for characteristic changes. Early in the course of the disease, the skull demonstrates predominantly lytic lesions. Over time, the bone thickens and enlarges as the osteoblasts remodel, and characteristic ‘‘cotton-wool’’ densities become visible on x-rays.
In rare cases, Paget's disease can have a malignant transformation, which occurs in approximately one percent of patients. The malignancies that can result from Paget's in order of frequency include osteogenic sarcoma, giant cell tumors, chondrosarcomas, malignant fibrous histiocytomas, and fibrosarcomas. If a patient is found to have a rapid increase in blood alkaline phosphatase levels, he or she should be screened for malignancy development.
BONUS VIDEOS: VISUAL DIAGNOSIS
Read this month's Clinical Consultation case, then watch the accompanying videos from Hamid R. Djalilian, MD, to review the patient's imaging for yourself.
- Video 1. Axial (horizontal) CT of the right temporal bone showing the Paget's changes in the temporal bone http://bit.ly/2qctCh7.
- Video 2. Axial (horizontal) CT of left temporal bone showing normal control http://bit.ly/2qdfFzr.
- Video 3. Coronal (vertical, parallel to face) CT of the right temporal bone showing the temporal bone changes in the coronal plane and the narrowing of the internal auditory canal http://bit.ly/2qbyza7.
- Video 4. Coronal (vertical, parallel to face) CT of the left temporal bone showing the normal temporal bone http://bit.ly/2qkwhWl.
- Video 5. Sagittal (vertical, parallel to auricle) CT of the right temporal bone showing the facial nerve canal and its course. The images start from the center of the head to the right auricle http://bit.ly/2CGHk3a.
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