A 22-year-old man comes in with complaints of ear blockage and possible cerumen impaction. He has been trying to clean his ear with a cotton swab but feels that his ear canal is blocked. He denies having extensive exposure to water or cold air. Examination of his right ear canal showed complete canal occlusion and bony growth under the skin at the bony cartilaginous junction. The left ear canal appeared normal. His audiogram is on the right.
Diagnosis: Fibrous Dysphasia
Bony growths in the ear canal are generally caused by one of two disease processes. Chronic exposure to cold water or cold air with water can result in the growth of bony protuberances along the external auditory canal's suture lines, where the tympanic bone interfaces with the petrous or squamous bone. Called exostoses or surfer ears, these growths are usually seen on the roof and the anterior and posterior walls of the external auditory canal. Over time, the bony exostoses can reach the center of the canal and cause blockage.
Patients with this condition generally show symptoms of ear canal occlusion such as water trapping or recurrent external auditory canal infection. This condition is frequently seen in surfers in the West Coast of the United States, where it is possible to surf in the ocean year-round. The combined exposure to water and wind causes the water to evaporate, thereby cooling the ear canal. This, in turn, instigates a reactive bone formation in the periosteum (covering of the bone). The same outcome from cold water exposure has been observed in patients who used cold water for nasal irrigation after a sinus surgery. Since the skin in the bony external canal is very thin, the periosteum is more exposed to cold temperatures, compared with other bones in the body that are covered by protective layers of fat and muscles.
Another condition characterized by one-sided bony growth is osteoma of the external auditory canal. An osteoma is a benign tumor of the bone that tends to occur in the bony cartilaginous junction. A surgery is usually done to remove occlusive osteomas.
In this case, the patient elected to have a surgical procedure to remove the bony growth in the right ear canal. A CT scan was performed in preparation for his surgery. CT scan of the right side of the temporal bone showed a ground-glass appearance in the mastoid area (Figs. 2, 3, 4). The patient's imaging results were most suspicious for fibrous dysplasia of the temporal bone, where the normal bone (bright white) is replaced by a “ground glass” (dark gray).
Fibrous dysplasia is a benign fibro-osseous disease. Known to have a generally slow progression, this disease can affect the bones of the skull, as well as the axial or appendicular skeleton. Fibrous dysphasia is caused by a congenital mutation of the G-protein subunit α gene on chromosome 20. Histologically, the normal bone in the affected area is slowly replaced with irregular fibrous tissue and mature trabecular bones. About 70 percent of cases are monostotic, wherein only a single bone in a single location is involved. Some cases can also be polyostotic, which involves multiple bones. Some patients with the polyostotic type of the disease have also been diagnosed with the McCune-Albright syndrome, a rare disorder characterized by precocious puberty and café-au-lait (brown) spots on the body.
Fibrous dysplasia can also affect the axial (spine) and appendicular (arms and legs) skeletons. When the axial or appendicular skeleton is involved, fibrous dysplasia most commonly presents with pain or as a fracture at the site of lesion. A fracture occurs because the affected bone is not as structured and strong as normal skeletal bone. When it's in the skull, fibrous dysplasia most commonly presents with pain as a mass or as a result of cranial neuropathies. Patients may have atypical facial pain, headaches, or sinus pain (a frequent site of lesions in the skull is the sinuses). Cranial neuropathies may include double vision, hearing loss, facial paralysis, facial paresthesia (numbness or tingling), among others.
Patients with fibrous dysplasia in the temporal bone will most commonly present with conductive hearing loss due to occlusion of the external auditory canal or involvement of the ossicles. The otic capsule bone is generally spared. However, stenosis of the internal auditory canal or the facial nerve fallopian canal can lead to hearing loss or facial paralysis. When symptomatic, patients may undergo surgery to recontour the bone and open the ear canal or to decompress the internal auditory canal or facial nerve. Since the fibrous dysplasia bone has a tendency to regrow, patients with this condition may require multiple procedures.
This patient underwent a transcanal procedure, which was performed using a micro-osteotome and an ultrasonic serrated knife (Otol Neurotol. 2016;37:1418 http://bit.ly/2jih2Ky;Otol Neurotol. 2016;37:185 http://bit.ly/2jihf0l). The transcanal technique is advantageous in reducing the need for multiple post-auricular incisions should the patient require additional surgeries. However, it is technically difficult and requires previous experience in treating exostoses.
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 CT of the right temporal bone showing the fibrous dysplasia bone encroaching on the canal from the anterior-posterior direction.
- Video 2. Axial CT of the left temporal bone showing the normal anatomy of the patient.
- Video 3. Coronal CT of the right temporal bone showing the fibrous dysplasia bone that is causing the narrowing of the canal from superior-inferior direction.
- Video 4. Coronal CT of the left temporal bone showing the normal canal thickness and the mastoid.
- Video 5. Sagittal CT of the right temporal bone showing the transcanal view (looking from the side). The area close to the tympanic membrane is spared in this patient.
- Video 6. Sagittal CT of the left temporal bone showing the normal transcanal view (looking from the outside of the ear inward).
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